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  • 1.
    Akram, Muhammad Nadeem
    et al.
    University of South-Eastern Norway, Norway.
    Baraas, Rigmor C.
    University of South-Eastern Norway, Norway.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Improved wide-field emmetropic human eye model based on ocular wavefront measurements and geometry-independent gradient index lens2018In: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 35, no 11, p. 1954-1967Article in journal (Refereed)
    Abstract [en]

    There is a need to better understand the peripheral optics of the human eye and their correction. Current eye models have some limitations to accurately predict the wavefront errors for the emmetropic eye over a wide field. The aim here was to develop an anatomically correct optical model of the human eye that closely reproduces the wavefront of an average Caucasian-only emmetropic eye across a wide visual field. Using an optical design program, a schematic eye was constructed based on ocular wavefront measurements of the right eyes of thirty healthy young emmetropic individuals over a wide visual field (from 40° nasal to 40° temporal and up to 20° inferior field). Anatomical parameters, asymmetries, and dispersion properties of the eye’s different optical components were taken into account. A geometry-independent gradient index model was employed to better represent the crystalline lens. The RMS wavefront error, wavefront shapes, dominant Zernike coefficients, nasal-temporal asymmetries, and dispersion properties of the developed schematic eye closely matched the corresponding measured values across the visual field. The developed model can help in the design of wide-field ophthalmic instruments and is useful in the study and simulations of the peripheral optics of the human eye.

    The full text will be freely available from 2019-11-30 09:42
  • 2.
    Alahamami, Mastour A.
    et al.
    Indiana University, USA.
    Elsner, Ann E.
    Aeon Imaging, USA;Indiana University, USA.
    Baskaran, Karthikeyan
    Indiana University, USA.
    YoussefAgha, Ahmed H.
    Indiana University, USA.
    Brahm, Shane
    Indiana University, USA.
    Young, Stuart B.
    Indiana University, USA.
    Litvin, Taras V.
    University of California Berkeley, USA.
    Ozawa, Glen Y.
    University of California Berkeley, USA.
    Cuadros, Jorge
    University of California Berkeley, USA.
    Muller, Matthew S.
    Aeon Imaging, USA.
    Investigation of Photoreceptors in Diabetic Macular Edema2014In: IOVS, Orlando, Florida, USA, 2014, Vol. 155(13)Conference paper (Refereed)
    Abstract [en]

    Abstract Purpose: To evaluate the photoreceptor integrity in diabetic patients with macular edema using spectral domain optical coherence tomography (SD-OCT) Methods: We compared macular thickness in diabetic patients with and without macular edema to determine the role of damage to the external limiting membrane (ELM) or photoreceptors. Diabetic patients were selected from the screening study of > 2000 minority patients seen at Eastmont Wellness Center, Oakland, CA. Patients underwent photoscreening with a Canon Cr-DGi nonmydriatic camera (Tokyo, Japan) and an iVue OCT (Optovue Inc, Fremont, CA). Retinal scans of 70 diabetic patients, age range 33-68 yr., were selected so that A) 50% of patients had clinical significant macular edema (CSME), as diagnosed by the presence of hard exudates within 1 disc diameter from the fovea in the color photos, B) the full range of central macular thicknesses in our population was included. And C) patients with CSME were the same age as those not diagnosed with CSME. We graded the retinal scans according to the external limiting membrane (ELM) integrity; 6 patients had damaged ELM and the remaining 64 had intact ELM. Similarly, we graded the retinal scans according to the photoreceptor integrity; 14 patients had damaged photoreceptors and the remaining 56 had intact photoreceptors Results: Average retinal thickness was 254 µm (±57.4) and 356 µm (±95.9) in patients with intact and damaged ELM, respectively; and was 240 µm (±30.0), and 363 µm (±90.0) in patients with intact and damaged photoreceptors, respectively. Retinal thickness means were significantly greater for patients with damaged compared with intact ELM ( P=0.031). Similarly, Retinal thickness means in patients with damaged photoreceptors were significantly greater compared to patients with intact photoreceptors ( P = 0.0001). We also observed that all 6 patients who have damaged ELM were diagnosed with CSME, but were not significantly older than the diabetic patients not diagnosed with CSME ( P = 0.393) Conclusions: ELM and photoreceptor layer damage are found more often when retinal thickness exceeds 355 µm. It is not known if this outer retinal damage is the result of the edema or whether there is more edema because the outer retinal blood brain barrier is failing

  • 3. Alahamami, Mastour A.
    et al.
    Elsner, Ann E.
    Indiana University School of Optometry, USA.
    Muller, Matthew S.
    Aeon Imaging, USA.
    Baskaran, Karthikeyan
    Indiana University School of Optometry, USA.
    Gast, Thomas J.
    Indiana University School of Optometry, USA.
    Litvin, Taras V.
    Indiana University School of Optometry, USA.
    Ozawa, Glen Y.
    University of California Berkeley, USA.
    Cuadros, Jorge
    University of California Berkeley, USA.
    Haggerty, Bryan P.
    Indiana University School of Optometry, USA.
    Malinovsky, Victor E.
    Indiana University School of Optometry, USA.
    Clark, Christopher A.
    Indiana University School of Optometry, USA.
    Brahm, Shane
    Indiana University School of Optometry, USA.
    Young, Stuart B.
    Indiana University School of Optometry, USA.
    Comparison of cysts in red and green images for diabetic macular edema2014Conference paper (Refereed)
    Abstract [en]

    Purpose: To improve the detection of macular cyst with photoscreening, we tested whether in a population of largely minority patients the red channel image from a color fundus camera visualizes cysts in diabetic macular edema better than the green channel image. In assessing diabetic retinas for clinically significant macular edema, the presence of cysts must be judged with respect to the central macula. Some grading programs use red free images, often derived from green channel images, to enhance visualization of retinal vessel damage or macular pigment, but some red and near infrared instruments have detected cysts better than short wavelength techniques. Methods: We evaluated macular cysts in 13 diabetic patients diagnosed with clinically significant macular edema, age range 33-68 years. Diabetic patients were selected from the screening study of >2000 underserved patients seen at Eastmont Wellness Center, Oakland, CA. Patients underwent photoscreening with a nonmydriatic color fundus camera (Canon Cr-DGi, Tokyo, Japan) and SD-OCT (iVue, Optovue Inc, Fremont, CA). The color fundus images for those patients were transformed into red and green channels to evaluate the appearance of macular cysts in red channel images and green channel images. The region of each cyst was compared SD-OCT scans (Adobe Photoshop CS5.1, San Jose, CA). Only cysts touching the central 1 mm around the fixation from the SD-OCT scans were sampled. Results: The average size of retinal cysts in red channel images, 124.57 µm (±106.96), was significantly greater than in green channel, 59.44 µm (±76.6), (p<0.006). Entire cysts could not be seen in 5 eyes in the green channel images. Conclusions: Our results indicate that the grading of cysts in the central macular might be improved by incorporating red channel images. There are a number of potential factors that could make cysts less visible in the green channel images, including poorer light penetration through to the deeper retina or macular pigment. Anterior segment issues impact more on green channel images. This population includes mostly minority patients who have dark fundi, and darker images.

  • 4.
    Alhamami, Mastour
    et al.
    Indiana University, USA.
    Elsner, Ann
    Indiana University, USA;Aeon Imaging, USA.
    Malinovsky, Victor
    Indiana University, USA.
    Clark, Christopher
    Haggerty, Bryan
    Indiana University, USA.
    Ozawa, Glen
    University of California, USA.
    Cuadros, Jorge A
    University of California, USA ; EyePACS, USA.
    Baskaran, Karthikeyan
    Indiana University, USA.
    Gast, Thomas
    Indiana University, USA;Aeon Imaging, USA.
    Litvin, Taras
    University of California, USA.
    Muller, Matthew
    Aeon Imaging, USA.
    Brahm, Shane
    Indiana University, USA.
    Young, Stuart
    Indiana University, USA.
    Miura, Masahiro
    Tokyo Medical University Ibaraki Medical Center, Japan.
    Comparison of Cysts in Red and Green Images for Diabetic Macular Edema2017In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 94, no 2, p. 137-149Article in journal (Refereed)
    Abstract [en]

    Purpose: To investigate whether cysts in diabetic macular edema are better visualized in the red channel of color fundus camera images, as compared with the green channel, because color fundus camera screening methods that emphasize short-wavelength light may miss cysts in patients with dark fundi or changes to outer blood retinal barrier.

    Methods: Fundus images for diabetic retinopathy photoscreening were acquired for a study with Aeon Imaging, EyePACS, University of California Berkeley, and Indiana University. There were 2047 underserved, adult diabetic patients, of whom over 90% self-identified as a racial/ethnic identify other than non-Hispanic white. Color fundus images at nominally 45 degrees were acquired with a Canon Cr-DGi non-mydriatic camera (Tokyo, Japan) then graded by an EyePACS certified grader. From the 148 patients graded to have clinically significant macular edema by the presence of hard exudates in the central 1500 [mu]m of the fovea, we evaluated macular cysts in 13 patients with cystoid macular edema. Age ranged from 33 to 68 years. Color fundus images were split into red, green, and blue channels with custom Matlab software (Mathworks, Natick, MA). The diameter of a cyst or confluent cysts was quantified in the red-channel and green-channel images separately.

    Results: Cyst identification gave complete agreement between red-channel images and the standard full-color images. This was not the case for green-channel images, which did not expose cysts visible with standard full-color images in five cases, who had dark fundi. Cysts appeared more numerous and covered a larger area in the red channel (733 +/- 604 [mu]m) than in the green channel (349 +/- 433 [mu]m, p < 0.006).

    Conclusions: Cysts may be underdetected with the present fundus camera methods, particularly when short-wavelength light is emphasized or in patients with dark fundi. Longer wavelength techniques may improve the detection of cysts and provide more information concerning the early stages of diabetic macular edema or the outer blood retinal barrier.

  • 5.
    Arthur, Edmund
    et al.
    Indiana University, USA.
    Young, Stuart B.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Elsner, Ann E.
    Muller, Matthew S.
    Gast, Thomas J.
    Haggerty, Bryan P.
    Clark, Christopher A.
    Brahm, Shane
    Litvin, Taras V.
    Ozawa, Glen Y.
    Cuadros, Jorge
    Individual Retinal Layer Thickness in Diabetic Patients with Clinically Significant Macular Edema: A Gender Based Analysis2016Conference paper (Refereed)
    Abstract [en]

    Purpose: To compare segmented retinal layer thicknesses between male and female diabetics with clinically significant macular edema (CSME). This study expands our earlier analysis of central macular thickness (CMT) measurements in diabetic males vs. females. Methods: Diabetic retinopathy screening of 2080 diabetics from Alameda County, CA, indicated 142 patients with CSME, as judged by EyePACS certified graders using color fundus images (Canon CR6-45NM). Of the 2080 diabetics, 1784 were imaged with SD-OCT (Optovue iVue). From the 142 patients, we selected 11 males with good fixation, CMT > 300 µm, and no other ocular complications, along with 11 females with the greatest values of CMT while controlling for age, HbA1c and diabetes duration. Manual segmentation of retinal layers using custom software (Mathworks Matlab) of the SD-OCT images of these subjects was done. We analyzed thicknesses for regions 1 deg - 2 deg for nasal and temporal retina in a B-scan centered on the fovea. A 2 X 2 ANOVA probed the differences in thickness for gender, meridian, and their interaction. We also analyzed the central 1 mm of the outer retinal layers, and performed t-tests. Results: Males had significantly thicker nerve fiber layer (NFL) (13.30 ± 2.85 µm) than females (10.13 ± 6.13 µm) and ganglion cell layer-inner plexiform layer (GCL-IPL) (62.54 ± 21.18 µm) than females (48.07 ± 25.91 µm), p < 0.05. There was no effect of meridian and no interaction (p > 0.05). All other layers except the retinal pigment epithelium (RPE) were thicker for males than females even though these were not significant (p > 0.05). There were no significant differences for the layers of the outer retina, which were highly variable and distorted by cysts. Conclusion: Outside the fovea, NFL and GCL-IPL thicknesses were significantly higher in males than females.

  • 6.
    Arthur, Edmund
    et al.
    Indiana University, USA.
    Young, Stuart B.
    Bowersox Vision Center, Shelbyville, USA.
    Elsner, Ann E.
    Indiana University, USA.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Papay, Joel A.
    Indiana University, USA.
    Muller, Matthew S.
    Aeon Imaging, LLC, Bloomington, USA.
    Gast, Thomas J.
    Indiana University, USA;Aeon Imaging, LLC, Bloomington, USA.
    Haggerty, Bryan P.
    Indiana University, USA.
    Clark, Christopher A.
    Indiana University, USA.
    Malinovsky, Victor E.
    Indiana University, USA.
    Brahm, Shane G.
    Peter Christensen Health Center, Lac Du Flambeau, USA.
    Litvin, Taras V.
    University of California, USA.
    Ozawa, Glen Y.
    University of California Berkeley, USA.
    Cuadros, Jorge A.
    University of California Berkeley, USA.
    Central Macular Thickness in Diabetic Patients: A Sex-based Analysis2019In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 96, no 4, p. 266-275Article in journal (Refereed)
    Abstract [en]

    SIGNIFICANCE The pathological changes in clinically significant diabetic macular edema lead to greater retinal thickening in men than in women. Therefore, male sex should be considered a potential risk factor for identifying individuals with the most severe pathological changes. Understanding this excessive retinal thickening in men may help preserve vision. PURPOSE The purpose of this study was to investigate the sex differences in retinal thickness in diabetic patients. We tested whether men with clinically significant macular edema had even greater central macular thickness than expected from sex differences without significant pathological changes. This study also aimed to determine which retinal layers contribute to abnormal retinal thickness. METHODS From 2047 underserved adult diabetic patients from Alameda County, CA, 142 patients with clinically significant macular edema were identified by EyePACS-certified graders using color fundus images (Canon CR6-45NM). First, central macular thickness from spectral domain optical coherence tomography (iVue; Optovue Inc.) was compared in 21 men versus 21 women without clinically significant macular edema. Then, a planned comparison contrasted the greater values of central macular thickness in men versus women with clinically significant macular edema as compared with those without. Mean retinal thickness and variability of central macular layers were compared in men versus women. RESULTS Men without clinically significant macular edema had a 12-μm greater central macular thickness than did women (245 ± 21.3 and 233 ± 13.4 μm, respectively; t40 = −2.18, P = .04). Men with clinically significant macular edema had a 67-μm greater central macular thickness than did women (383 ± 48.7 and 316 ± 60.4 μm, P < .001); that is, men had 55 μm or more than five times more (t20 = 2.35, P = .02). In men, the outer-nuclear-layer thickness was more variable, F10,10 = 9.34. CONCLUSIONS Underserved diabetic men had thicker retinas than did women, exacerbated by clinically significant macular edema.

  • 7.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Optimal Use of Peripheral Vision2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    People who lose their central vision have to rely on their peripheral vision for all visual tasks. The ability to resolve fine details in the periphery is reduced due to retinal limitations and the optical aberrations arising from the use of off-axis vision. The aim of this work is to improve vision by enhancing the image quality at the preferred retinal locus by means of correcting the optical errors. The focus of this thesis has been to measure and correct peripheral optical errors, as well as to evaluate their impact on resolution acuity in both normal and central visual field loss subjects.

     In order to measure peripheral optics we employed a COAS HD VR open view aberrometer which is based on the Hartmann-Shack principle. Psychophysical methods were used to evaluate peripheral grating resolution acuity. We assessed the repeatability of the wavefront sensor in measuring the peripheral ocular aberrations. The symmetry of peripheral ocular aberrations between the left and right eyes was examined. The influence of age on peripheral ocular aberrations was also investigated. We evaluated peripheral vision with sphero-cylindrical correction in healthy eyes and performed the first adaptive optics aberration correction at the preferred retinal locus of a single central visual field loss subject.

     We found that the aberrometer was repeatable and reliable in measuring peripheral ocular aberrations. There was mirror symmetry between the two eyes for most of the peripheral aberration coefficients. Age had a significant influence on peripheral ocular aberrations; there were larger amounts of higher-order aberrations in old eyes than in young eyes. Peripheral low contrast resolution acuity improved with peripheral refractive correction in subjects who had higher amounts of off-axis astigmatism. Finally, adaptive optics aberration correction improved both high and low contrast resolution acuity measured at the preferred retinal locus of the single low vision subject.

     Because of their versatility, open view aberrometers will hopefully be a standard clinical instrument at low vision clinics as they allow for measurements to be rapidly performed at any location in the visual field. The existence of off-axis astigmatism should be better communicated within the low-vision rehabilitation community. Currently, the off-axis refractive errors can be corrected with conventional methods and we hope that the higher-order aberrations can also be corrected in a more realistic ways in the future.  

     In conclusion, this thesis has shown that peripheral visual function can be improved by optical correction. The findings of this thesis have broadened the knowledge of peripheral optical errors and their influence on vision.

  • 8.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Calabrèse, Aurélie
    Castet, Eric
    Moreno, Laura
    Silva, Marta
    Macedo, António Filipe
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Scoring reading parameters: an inter-rater reliability study using the MNREAD test2017Conference paper (Refereed)
    Abstract [en]

    Aim: Estimating MNREAD parameters such as Critical Print Size (CPS) and Maximum Reading Speed (MRS) - using the time taken to read blocks of text - often requires subjective analysis of the reading profile. Depending on the rater, parameters may be over- or under-estimated, resulting in difficult or even impossible between-study comparisons. The aim of this project was to evaluate the inter-rater reliability of MNREAD parameters in subjects with visual impairment. Methods: Reading times for the Portuguese version of the MNREAD chart from 32 subjects, reading binocularly were analyzed. Reading speed was computed by a single experimenter (AFM) using reading time and number of errors. Based on reading speeds, three experimented raters (AFM, AC and KB) computed MRS and CPS using the following method. CPS was defined as the print size at which subsequent smaller print sizes were read at 1.96 x standard deviation slower than the mean of the preceding print sizes; MRS was estimated as the mean reading speed for sentences in print larger than the CPS. Inter-rater reliability was assessed using intra-class correlation (ICC) coefficient for both MRS and CPS for all three raters. Results: Near acuity range was 0.14-1.9 logMAR. The average measure ICC for CPS was 0.896 with a 95% CI from 0.814 to 0.946 (p< 0.001). The average measure ICC for MRS was 0.984 with a 95% CI from 0.970 to 0.992 (p< 0.001). Conclusion: A high degree of reliability was found between the three raters for both CPS and MRS. Even though some small variability exists this may be due to raters’ high-level experience with MNREAD data. Future directions will involve: 1) including more raters with various level of experience in MNREAD rating; 2) investigating the degree of inter-rater reliability for raters using different estimation methods.

  • 9.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Ekblad, Johan
    SYAB, Kalmar.
    Inde, Krister
    Indenova, Karlstad.
    Melis-Dankers, Bart
    Royal Dutch Visio, Centre of Expertise for Blind and Partially Sighted People, Netherlands.
    Driving performance in participants with quadrantanopia and hemianopia in Sweden: a closed circuit driving track study2015Conference paper (Refereed)
    Abstract [en]

    Background: The ability to drive a car is one of the important aspect of a person’s independent lifestyle. People with visual field defects after stroke or traumatic brain injury (TBI) have more limitations in driving. In Sweden, they are not allowed to drive and their driving licenses are revoked. The Swedish transport agency does not allow any on-road test for them to prove their practical fitness to drive. Therefore, the aim was to evaluate driving performance in participants with visual field defects after TBI in a closed circuit driving track.Methods: Eleven participants with varying degrees of quadrantanopia and hemianopia after TBI were recruited for this study. The mean age of the participants was 58 ±13.7 years (37 - 73 years). All participants underwent 10 weeks of explorative saccadic training at the hospital prior to driving assessment. Driving performance were assessed by two driving instructors and they graded the participants from 1 (fail) to 5 (excellent) on the following five categories: maneuvering the vehicle, safety margin, traffic rules, scanning for potential hazards and reacting to situations. The subject passed the driving test only if they scored 3 or more in each category.Results: Five (45%) out of 11 participants passed the driving test and they were adjudged as fit to drive. Remaining six (55%) participants failed at least in one category. Three of them failed in visual scanning, two failed in maneuvering and one failed in both the aforementioned categories as well as safety margin.Discussion: A rehabilitation program aimed at improving safe driving should be implemented and an on-road assessment of fitness to drive should be allowed in Sweden for this population in future.Conclusion: The decision on practical fitness to drive cannot be based solely on the presence of visual field defect and an on-road assessment is required.

  • 10.
    Baskaran, Karthikeyan
    et al.
    Indiana University, USA.
    Elsner, Ann E.
    Indiana University, USA ; Aeon Imaging, USA.
    Muller, Matthew S.
    Aeon Imaging, USA.
    Haggerty, Bryan P.
    Indiana University, USA.
    Papay, Joel A.
    Indiana University, USA.
    Gast, Thomas
    Indiana University, USA ; Aeon Imaging, USA.
    Litvin, Taras V.
    University of California Berkeley, USA.
    Ozawa, Glen Y.
    University of California Berkeley, USA.
    Cuadros, Jorge
    University of California Berkeley, USA.
    Petrig, Benno L.
    Aeon Imaging, USA.
    Stability of fixation in diabetes patients with and without clinically significant macular edema2014Conference paper (Refereed)
    Abstract [en]

    Purpose - Eye diseases affecting central vision impair fixation and interfere with day-to-day tasks such as reading. Diabetic retinopathy and clinically significant macular edema (CSME) are leading causes of visual impairment in diabetes patients. The aim of this study is to find whether diabetic patients with CSME have poorer fixation stability compared to patients without CSME, by analyzing the fundus images obtained from the Laser Scanning Digital Camera (LSDC).

    Methods - Two hundred underserved, diabetic patients were screened for diabetic retinopathy at the Eastmont Wellness Center within the EyePACS telemedicine network, using LSDC. One eye of each patient who had diabetic retinopathy was included in this study. Non-mydriatic color fundus photos were classified for presence of CSME by two independent, certified EyePACS graders. The first 50 patients (25 males &amp; 25 females) with CSME were selected and 50 (27 males &amp; 23 females) diabetic patients without CSME were selected as controls. Mean age was 59 (±9) years for patients with CSME and was 55 (±10) years for patients without CSME. The subjects included 53% Hispanics, 26% African Americans and 21% other. A series of 20 images (36 deg field, 1024 X 1024 pixels, and 850 nm) were acquired at 11 fps. Eye positions were obtained by selecting a region of interest in the first image of each series and aligning the remaining images to that region by cross-correlation. The bi-contour ellipse area (BCEA) and the standard deviation of the Euclidean distance (SDED) were used to quantify fixation stability.

    Results - The fixation stability for patients with CSME was significantly worse than for those without CSME (t test: p &lt; 0.001, 0.007 for BCEA and SDED, respectively). The mean fixation stability obtained by the BCEA metric was 2.74 (±0.40) log(minArc2) and 2.34 (±0.42) log(minArc2) for patients with and without CSME, respectively. For SDED the mean was 48.4 (±28.8) microns and 34.6 (±20.4) microns for patients with and without CSME, respectively. The correlation with age was not significant for either group (R2 = 0.052, 0.011).

    Conclusions - Diabetic patients with CSME had poorer fixation stability than patients without CSME for both metrics. Fixation stability is a potential tool for assessing macular function and could be used for tracking the treatment and progression of macular edema.The LSDC images provide one method to quantify fixation stability rapidly.

  • 11.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Inde, Krister
    Ekblad, Johan
    Melis-Dankers, Bart
    Closed circuit driving performance in persons with quadrantanopia and hemianopia in Sweden2016In: Scandinavian Journal of Optometry and Visual Science, ISSN 1891-0882, E-ISSN 1891-0890, Vol. 9, no 2, p. 14-Article in journal (Refereed)
    Abstract [en]

    In Sweden, persons with homonymous visual field defects (HVFDs) are not allowed to drive and usually their driving licences are revoked. Although earlier studies (de Haan et al. 2014; Elgin et al. 2010) have shown that HVFDs do not necessarily impair practical fitness to drive, the Swedish transport agency does not allow them any on-road driving testing to prove their practical fitness to drive. The aim of this study was to evaluate driving performance in participants with visual field defects after acquired brain injury in a closed circuit driving track. Eleven former drivers with varying degrees of quadrantanopia and hemianopia after acquired brain damage were recruited for this study from the stroke rehabilitation department at Kalmar County Hospital. The median age of the participants was 55 years and their age ranged from 37 to 73 years. Driving performance was assessed by two experienced driving instructors. They graded the participants on a scale from 1 (major faults) to 5 (excellent) on the following five categories: manoeuvring the vehicle, risk assessment, traffic rules, visual scanning and situation awareness. The subject would pass the driving test only if they had scored 3 or more in each category. The subjects who passed the closed circuit driving track test were evaluated further with a driving simulator. Five (45%) out of 11 participants passed the driving test and were adjudged as fit to drive. The remaining six (55%) participants failed in at least one category. Three failed in visual scanning, two failed in manoeuvring and one failed in both the aforementioned categories as well as risk assessment. Three subjects who passed the closed circuit driving track test were also evaluated in a driving simulator. Out of the three subjects, only one was able to complete and pass the evaluation while the remaining two participants aborted the evaluation due to simulator sickness. Homonymous visual field defects do not necessarily impair fitness to drive. Therefore, an on-road assessment of practical fitness to drive should be allowed in Sweden for this population in the near future. The decision on practical fitness to drive cannot be based solely on the presence of visual field defects. A rehabilitation program aimed at improving safe driving should be put into practice with an on-road driving training and assessment procedure. It should be developed and implemented by experienced traffic inspectors as a complementary part of the decision to either issue or revoke a driving licence for this population.

  • 12.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Inde, Krister
    SMS Projektgrupp, .
    SYAB Kalmar, .
    SMS resultatrapporten2015Report (Refereed)
  • 13.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Lewis, Peter
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Rosen, Robert
    Biomedical and X-Ray Physics.
    Unsbo, Peter
    Biomedical and X-Ray Physics.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Effects of Optical Defocus on Resolution Acuity in Preferred Retinal Locus2011In: Invest Ophthalmol Vis Sci 2011;52: E-Abstract 1900., 2011, Vol. 52, no 6Conference paper (Refereed)
    Abstract [en]

    PurposeResolution acuity in the peripheral visual field is primarily limited by retinal sampling. In healthy eyes, the correction of peripheral refractive errors does not produce significant visual benefits other than improved detection and low contrast acuity. However, studies (Lundstrom L et al, Optom Vis Sci, 2007;84:1046-52) have shown that peripheral refractive corrections improve resolution acuity in subjects with central visual field loss (CFL) who have an established preferred retinal locus (PRL). The aim of this study was to evaluate the effect of optical defocus on high contrast resolution acuity in the PRL. MethodsResolution acuity was evaluated under spherical defocus in the PRL of three low vision subjects (mean age 75 years) with long standing CFL (due to age-related macular degeneration). Off-axis refractive error at the PRL was measured by an open-field COAS-HD VR aberrometer and was corrected accordingly. The PRL for subject 1 was located at 10{degrees} in the temporal visual field (left eye), subject 2 at 20{degrees} in the nasal visual field (right eye) and subject 3 at 15{degrees} in the inferior visual field (left eye). Stimuli consisting of high-contrast Gabor patches with a visible diameter of 3{o} were presented on a CRT monitor situated 1.0 meter from the subject. Resolution thresholds for static visual acuity (SVA) and dynamic visual acuity (DVA) were obtained using an adaptive Bayesian algorithm. Fixation was aided using illuminated concentric rings covering {+/-}25{degrees} in the visual field. Defocus was altered in 1D steps up to {+/-}4D. When measuring DVA, the sine-wave gratings drifted within the Gaussian envelope at an angular velocity of 1{degrees}/sec. ResultsResolution thresholds for both SVA and DVA in the PRL varied significantly with the amount of optical defocus. The results show a 2 - 3 line decrease (logMAR) in SVA and DVA with 4 D positive and negative defocus. There was no significant difference between SVA and DVA with increasing defocus. In the absence of defocus, SVA was significantly better than DVA in the PRL. ConclusionsDefocus as low as one dioptre has an impact on both static and dynamic high contrast resolution acuity for CFL subjects using a PRL. The results of this study suggest that, for CFL subjects using a PRL, resolution acuity is not only sampling limited but also influenced by the optics of the eye.

  • 14.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Macedo, António Filipe
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Calabrèse, Aurélie
    Aix-Marseille University, France.
    Rater and algorithm data of maximum reading speed (MRS) and critical print size (CPS) of 101 low vision participants.2019Data set
  • 15.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Macedo, António Filipe
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry. University of Minho Braga, Portugal.
    He, Yingchen
    University of Minnesota, USA.
    Hernandez-Moreno, Laura
    University of Minho Braga, Portugal.
    Queirós, Tatiana
    Hospital de Braga, Portugal.
    Mansfield, J. Stephen
    SUNY College at Plattsburgh, USA.
    Calabrèse, Aurélie
    Aix-Marseille University, France;CNRS, France.
    Scoring reading parameters: An inter-rater reliability study using the MNREAD chart2019In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 14, no 6, p. 1-14, article id e0216775Article in journal (Refereed)
    Abstract [en]

    Purpose First, to evaluate inter-rater reliability when human raters estimate the reading performance of visually impaired individuals using the MNREAD acuity chart. Second, to evaluate the agreement between computer-based scoring algorithms and compare them with human rating. Methods Reading performance was measured for 101 individuals with low vision, using the Portuguese version of the MNREAD test. Seven raters estimated the maximum reading speed (MRS) and critical print size (CPS) of each individual MNREAD curve. MRS and CPS were also calculated automatically for each curve using two different algorithms: the original standard deviation method (SDev) and a non-linear mixed effects (NLME) modeling. Intra-class correlation coefficients (ICC) were used to estimate absolute agreement between raters and/or algorithms. Results Absolute agreement between raters was ‘excellent’ for MRS (ICC = 0.97; 95%CI [0.96, 0.98]) and ‘moderate’ to ‘good’ for CPS (ICC = 0.77; 95%CI [0.69, 0.83]). For CPS, inter-rater reliability was poorer among less experienced raters (ICC = 0.70; 95%CI [0.57, 0.80]) when compared to experienced ones (ICC = 0.82; 95%CI [0.76, 0.88]). Absolute agreement between the two algorithms was ‘excellent’ for MRS (ICC = 0.96; 95%CI [0.91, 0.98]). For CPS, the best possible agreement was found for CPS defined as the print size sustaining 80% of MRS (ICC = 0.77; 95%CI [0.68, 0.84]). Absolute agreement between raters and automated methods was ‘excellent’ for MRS (ICC = 0.96; 95% CI [0.88, 0.98] for SDev; ICC = 0.97; 95% CI [0.95, 0.98] for NLME). For CPS, absolute agreement between raters and SDev ranged from ‘poor’ to ‘good’ (ICC = 0.66; 95% CI [0.3, 0.80]), while agreement between raters and NLME was ‘good’ (ICC = 0.83; 95% CI [0.76, 0.88]). Conclusion For MRS, inter-rater reliability is excellent, even considering the possibility of noisy and/or incomplete data collected in low-vision individuals. For CPS, inter-rater reliability is lower. This may be problematic, for instance in the context of multisite investigations or follow-up examinations. The NLME method showed better agreement with the raters than the SDev method for both reading parameters. Setting up consensual guidelines to deal with ambiguous curves may help improve reliability. While the exact definition of CPS should be chosen on a case-by-case basis depending on the clinician or researcher’s motivations, evidence suggests that estimating CPS as the smallest print size sustaining about 80% of MRS would increase inter-rater reliability.

  • 16.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Olsson, Roger
    Theagarayan, Baskar
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Effect of accommodation on peripheral refraction in myopes and emmetropes using a COAS-HD VR open field aberrometer.2016Conference paper (Refereed)
    Abstract [en]

    Purpose To investigate the effect of accommodation on both central and peripheral refractive errors in myopes compared to emmetropes using a COAS-HD VR open field aberrometer. Methods 15 myopic subjects (-1.50 D to -8.25 D) and 14 emmetropic subjects (+0.75 D to -0.25 D) participated in this study. The mean age of the myopic group was 24.3 ± 5.7 years and for the emmetropic group was 23.9 ± 5.7 years. Central and peripheral refraction were measured with a COAS-HD VR open field instrument at seven different eccentricities from 0° to ± 30° in 10° steps for three different accommodative demands 0.33 D, 2.50 D and 4.0 D during monocular viewing. The myopic subjects were corrected with soft contact lenses and the measurements were performed on the right eye for a 3 mm pupil diameter for both groups. Relative peripheral refractive error (RPRE) was calculated for all three accommodative demands for both groups. Results Repeated measures ANOVA showed no significant difference in RPRE across eccentricities or between accommodation demands in the myopes (pÂż0.05). The myopic group had minimal hyperopic shift in the periphery for all three accommodative demands. The largest mean hyperopic shift was 0.37 D at 30° nasal retina for an accommodative demand of 4.0 D. On the other hand, the emmetropic group became relatively myopic at peripheral eccentricities, from 20° onwards for all three accommodative demands. The largest mean myopic shift was 1.01 D at 30° temporal retina for an accommodative demand of 2.50 D. Conclusion In the myopic group, we did not find any significant reduction in hyperopic shift in the periphery with accommodation. The emmetropic group showed myopic shift in the periphery for all three accommodative demands with temporal retina being more myopic than nasal retina.

  • 17.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Rosen, R.
    Lewis, Peter
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Unsbo, P.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Benefit of Adaptive Optics Aberration Correction at Preferred Retinal Locus2012In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 89, no 9, p. 1417-1423Article in journal (Refereed)
    Abstract [en]

    PURPOSE.: To investigate the effect of eccentric refractive correction and full aberration correction on both high- and low-contrast grating resolution at the preferred retinal locus (PRL) of a single low-vision subject with a long-standing central scotoma. METHODS.: The subject was a 68-year-old women with bilateral absolute central scotoma due to Stargardt disease. She developed a single PRL located 25 degrees nasally of the damaged macula in her left eye, this being the better of the two eyes. High- (100%) and low-contrast (25 and 10%) grating resolution acuity was evaluated using four different correction conditions. The first two corrections were solely refractive error corrections, namely, habitual spectacle correction and full spherocylindrical correction. The latter two corrections were two versions of adaptive optics corrections of all aberrations, namely, habitual spectacle correction with aberration correction and full spherocylindrical refractive correction with aberration correction. RESULTS.: The mean high-contrast (100%) resolution acuity with her habitual correction was 1.06 logMAR, which improved to 1.00 logMAR with full spherocylindrical correction. Under the same conditions, low-contrast (25%) acuity improved from 1.30 to 1.14 logMAR. With adaptive optics aberration correction, the high-contrast resolution acuities improved to 0.89/0.92 logMAR and the low-contrast acuities improved to 1.04/1.06 logMAR under both correction modalities. The low-contrast (10%) resolution acuity was 1.34 logMAR with adaptive optics aberration correction; however, with purely refractive error corrections, she was unable to identify the orientation of the gratings. CONCLUSIONS.: Correction of all aberrations using adaptive optics improves both high- and low-contrast resolution acuity at the PRL of a single low-vision subject with long-standing absolute central scotoma

  • 18.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Theagarayan, Baskar
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Carius, Staffan
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Influence of age on peripheral aberration2010Conference paper (Refereed)
    Abstract [en]

    The purpose of this study is to compare peripheral higher order aberrations in young

    and old emmetropic eyes across the horizontal (±40°) and inferior (–20°) visual field.

    Introduction

     

     

    People with central visual field loss use eccentric fixation for various visual tasks.

    Recently studies have shown that the correction of lower order aberrations (defocus &

    astigmatism) can improve eccentric vision in subjects with central visual field loss

    (CFL)[1]. The CFL subjects mostly correspond to older age groups who use eccentric

    fixation angles up to 20°–30°. While there have been studies comparing the off-axis

    lower order aberrations in normal young and old subjects[2], there is only one recent

    study, which has compared off-axis higher order aberrations in normal young and old

    emmetropic eyes up to 20° (horizontal and vertical) eccentricity[3]. In this study we

    have measured off-axis aberrations in a group of 10 young (23 ± 3 years) and 10 old

    (57 ± 4 years) emmetropes. The aberrations of the right eye were measured using

    COAS-HD VR Hartmann-Shack aberrometer in steps 10° out to ± 40° horizontally and

    –20° inferiorly in the visual field. Subjects rotated the eyes to view the fixation targets,

    which were red light emitting diodes, placed at 3 meter from the eye. The aberrations

    were quantified for a pupil area 5 mm in diameter.

    Discussion

     

     

    Mixed between-within subject’s analysis of variance of the horizontal coma C13

    showed that there was a statistically significant difference between age groups

    (p<0.05). The coma increased linearly in both groups from nasal to temporal visual

    field. The rate of change was greater in the old (slope = –0.027 μm/deg) compared

    to the young (slope = –0.012 μm/deg) emmetropes. In the inferior visual field,

    vertical coma C-13 changed linearly in both groups with higher values in old (slope =

    0.015 μm/deg) compared to young (slope = 0.006 μm/deg). The mean spherical

    aberration was positive in older emmetropes (0.053 μm) compared to young

    emmetropes (-0.030 μm). The HO RMS showed a quadratic increase in the

    periphery for both age groups. The HO RMS was greater in older emmetropes but it

    was not statistically significant (p>0.05) when compared to young emmetropes.

     

    Conclusions

     

     

    Our results show that there is an increase in coma, spherical aberration, and HO

    RMS with age in the periphery.

  • 19.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Theagarayan, Baskar
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Carius, Staffan
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Measurement of Off-axis Refraction with a Commercial Open Field Aberrometer2010Conference paper (Refereed)
    Abstract [en]

    Purpose:

    People with central visual field loss (CFL) use their remaining peripheral vision in order to see better when performing various visual related tasks. At large off-axis angles, the eccentric vision can be limited both by the low resolution capacity of the peripheral retina and by the optical aberrations caused due to oblique angles. Previous work has shown that eccentric correction of induced off-axis astigmatism can improve vision in a preferred retinal location (PRL) for people with CFL. However, the eccentric refraction is often difficult to determine with traditional refractive methods. This work therefore shows the use of a commercially available wavefront sensor to measure fast and reliable off-axis refraction. Data on off-axis refraction is also of interest in the field of myopia research.

    Methods:

    We used the new open-field high-definition complete ophthalmic analysis system, COAS HD -VR, to evaluate off-axis refraction. Using the special Vision Research tool in this system stimulus (fixation objects) can be presented in a large part of the visual field. The instrument can measure out to 40 degrees in the horizontal visual field and 20 degrees in the vertical visual field with a range from sphere +7 D to − 17 D. It measures astigmatism up to 10 D. This instrument also allows natural binocular viewing without obstacles. Aberrations of the right eye of 30 emmetropes (24 ± 4 years) were studied. Off-axis refraction and higher order (HO) aberrations were measured in steps of 10° out to ± 30° in the horizontal visual field

    Results:

    The first data on young emmetropic eyes with this new instrument showed promising results for low (LO) and higher order (HO) aberrations in the peripheral visual field. Of the LO aberrations, astigmatism increased significantly with the off–axis angle, from 0.25 D at 10° Nasal to 1.65 D at 30° Nasal. In the HO aberrations, coma (C13) showed a linear increase across the horizontal visual field (p < 0.05)

    Conclusions:

    The COAS HD-VR shows promising results and good usability for future research in evaluation of off-axis refraction. In future we believe the aberrometer can be used clinically to measure off-axis refractions in low vision patients.

  • 20.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Theagarayan, Baskar
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Carius, Staffan
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Ocular Aberrations in the Peripheral Visual Field With a Commercial Open-View Aberrometer2010In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 51, no 5, article id 3951Article in journal (Refereed)
    Abstract [en]

    PurposeThe interest in off-axis aberrations has increased with the discovery of a possible link between myopia development and peripheral optics. The most common technology to measure the off-axis aberrations is a Shack-Hartmann wavefront aberrometer. This is the first study to report peripheral aberrations in a large sample of emmetropic population with a commercial open-view Shack-Hartmann aberrometer. MethodsThe commercial open-view Shack-Hartmann aberrometer COAS-HD VR was used to measure the aberrations in the peripheral vision. Aberrations of the right eye of 30 emmetropes (24 {+/-} 4 years) were studied. Off-axis aberrations were measured in steps of 10{degrees} out to {+/-} 30{degrees} in the horizontal visual field. The subjects turned their eye to view the off-axis fixation target (light emitting diode placed at 3 meters) during the measurement. The resulting wavefront aberrations were parameterized with Zernike coefficients for a 5 mm diameter pupil. All analyzes are reported according to optical society of America (OSA) recommended standards. ResultsAberrations from the 2nd to 6th order and the total higher-order root-mean-square (HO RMS) were analyzed using one-way ANOVA. The defocus C02 was significantly myopic in the nasal visual field (+20{degrees}, +30{degrees}) whereas there was no significant difference in the temporal visual field. Astigmatism C22 increased quadratically from {+/-}10{degrees} in the periphery and coma C13 showed a linear increase across the horizontal visual field (p < 0.05). The spherical aberration C04 and the total HO RMS showed a significant change at {+/-}30o. ConclusionsOur results showed that in young emmetropes there was a significant increase of HO RMS at {+/-}30{degrees}, which is expected. Astigmatism, horizontal coma, and spherical aberration vary systematically across the horizontal visual field in agreement with Seidel theory. The findings of our study with a large sample of emmetropic population agree with the previous studies done with laboratory built aberrometers.

  • 21.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Theagarayan, Baskar
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Carius, Staffan
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Repeatability of Peripheral Aberrations in Young Emmetropes2010In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 87, no 10, p. 751-759Article in journal (Refereed)
    Abstract [en]

    PURPOSE.: The purpose of this study is to assess the intrasession repeatability of ocular aberration measurements in the peripheral visual field with a commercially available Shack-Hartmann aberrometer (complete ophthalmic analysis system-high definition-vision research). The higher-order off-axis aberrations data in young healthy emmetropic eyes are also reported.

    METHODS.: The aberrations of the right eye of 18 emmetropes were measured using an aberrometer with an open field of view that allows peripheral measurements. Five repeated measures of ocular aberrations were obtained and assessed in steps of 10 degrees out to +/-40 degrees in the horizontal visual field (nasal + and temporal -) and -20 degrees in the inferior visual field. The coefficient of repeatability, coefficient of variation, and the intraclass correlation coefficient were calculated as a measure of intrasession repeatability.

    RESULTS.: In all eccentric angles, the repeatability of the third- and fourth-order aberrations was better than the fifth and sixth order aberrations. The coefficient of variation was <30% and the intraclass correlation coefficient was >0.90 for the third and fourth order but reduced gradually for higher orders. There was no statistical significant difference in variance of total higher-order root mean square between on- and off-axis measurements (p > 0.05). The aberration data in this group of young emmetropes showed that the horizontal coma (C13) was most positive at 40 degrees in the temporal field, decreasing linearly toward negative values with increasing off-axis angle into the nasal field, whereas all other higher-order aberrations showed little or no change.

    CONCLUSIONS.: The complete ophthalmic analysis system-high definition-vision research provides fast, repeatable, and valid peripheral aberration measurements and can be used efficiently to measure off-axis aberrations in the peripheral visual field

  • 22.
    Baskaran, Karthikeyan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Unsbo, Peter
    Biomedical and X-Ray Physics.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Influence of age on peripheral ocular aberrations.2011In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 88, no 9, p. 1088-1098Article in journal (Refereed)
    Abstract [en]

    PURPOSE.: To compare peripheral lower and higher order aberrations across the horizontal (±40°) and inferior (-20°) visual fields in healthy groups of young and old emmetropes. METHODS.: We have measured off-axis aberrations in the groups of 30 younger (24 ± 3 years) and 30 older (58 ± 5 years) emmetropes. The aberrations of OD were measured using the COAS-HD VR Shack-Hartmann aberrometer in 10° steps to ±40° horizontally and -20° inferiorly in the visual field. The aberrations were quantified with Zernike polynomials for a 4 mm pupil diameter. The second-order aberration coefficients were converted to their respective refraction components (M, J45, and J180). Mixed between-within subjects, analysis of variance were used to determine whether there were significant differences in the refraction and aberration components for the between-subjects variable age and the within-subjects variable eccentricity. RESULTS.: Peripheral refraction components were similar in both age groups. Among the higher order coefficients, horizontal coma (C3) and spherical aberration (C4) varied mostly between the groups. Coma increased linearly with eccentricity, at a more rapid rate in the older group than in the younger group. Spherical aberration was more positive in the older group compared with the younger group. Higher order root mean square increased more rapidly with eccentricity in the older group. CONCLUSIONS.: Like the axial higher order aberrations, the peripheral higher order aberrations of emmetropes increase with age, particularly coma and spherical aberration.

  • 23. Bharadwaj, S.R.
    et al.
    Hoenig, MP
    Sivaramkrishnan, VC
    Baskaran, Karthikeyan
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Simonian, D
    Mau, K
    Rastani, S
    Schor, CM
    Variation of Binocular-Vertical Fusion Amplitude with Convergence.2007In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 48, no 4, p. 1592-1600Article in journal (Refereed)
  • 24.
    Boström, Johanna
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Pettersson, Lovisa
    ,Karolinska Institutet.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Källmark, Fredrik
    Källmarkskliniken, Stockholm.
    Gierow, Peter
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Meibography: Inter-rater reliability2016In: 8th International Conference on the Tear Film & Ocular Surface: Basic Science and Clinical Relevance: Conference Program & Abstract Book, 2016, p. 47-Conference paper (Refereed)
    Abstract [en]

    Purpose. The tear film lipid layer holds an important role in maintaining the integrity and health of the anterior surface of the eye. The meibomian glands found in eyelids are responsible for producing most of the lipids of the tear film. Dysfunction of the meibomian glands leads to increased evaporation of tears, which may lead to dry eye. Meibography is a method used for assessing the drop out of meibomian glands. The aim of this study was to evaluate the reliability between two different examiners when rating meibography images. Methods. The Sirius 3D scheimpflug camera (C.S.O., Florence, Italy) was used to photograph the everted upper and lower eyelids of the right and left eye of 52 subjects. The grade of meibomian gland loss was subjectively graded using the five-grade Meiboscale (Pult, 2012) and the percentage of gland loss was calculated using Phoenix Meibography software (version 3.0.1.021, bon Optic VertriebsGmbH, Lübeck, Germany). Data was analyzed using MedCalc for Windows (version 16.4.3, MedCalc Software, Ostend, Belgium). Results. The inter-rater reliability for the Meiboscale grade of meibomian gland loss was calculated using weighted Cohen’s kappa (linear weights). The result for all 208 images was Kw = 0.542 (95 % CI 0.454 to 0.630), which indicates a moderate agreement. The inter-rater reliability for the percentage of meibomian gland loss was calculated using intraclass correlation coefficient. The result for all 208 images was ICC = 0.794 (95 % CI 0.737 to 0.839), which indicates a substantial agreement. Conclusions. Imaging is an invaluable tool when managing patients in clinical practice. When performing meibography to evaluate meibomian gland loss, using software to calculate the percentage of gland loss gives a better inter-rater agreement than subjective grading of the images.

  • 25. Chekitaan, S
    et al.
    Baskaran, Karthikeyan
    Department of Paediatric Ophthalmology and Strabismus, Medical and Vision Research Foundation, Sankara Nethralaya, 18 College Road, Chennai, 600006, India .
    Meenakshi, S
    The results of treatment of anisomyopic and anisohypermetropic amblyopia2008In: International ophtalmology, ISSN 0165-5701, E-ISSN 1573-2630, Vol. 29, no 4, p. 231-237Article in journal (Refereed)
    Abstract [en]

    Purpose To analyze the results of treatment of anisomyopic and anisohypermetropic amblyopia comparing full-time and part-time occlusion. Methods Retrospective analysis of case records of 100 patients of anisometropic amblyopia was carried out. Age, visual acuity, cycloplegic refraction, response, and compliance to treatment were recorded. Full-time occlusion (FTO) or part-time occlusion (PTO) was prescribed as treatment. Results The age of children ranged from 4 to 13 years (mean 7.65 years). In total, 66% of the patients were anisomyopic and 34% were anisohypermetropic. FTO was prescribed in 64 (64%), PTO in 29 (29%). Follow-up ranged from 1 to 24 months. The paired t-test revealed significant improvement of mean visual acuity in the FTO group (t = 13.272) compared with the PTO group (t = 7.386). A final visual acuity of 6/9 or better was achieved by 51% (34/66) anisomyopic amblyopes and 52% (18/34) anisohypermetropic amblyopes. Noncompliance to the treatment was 21%. Occlusion amblyopia was seen in four (4%) of the children. Conclusion FTO is superior to PTO for the treatment of amblyopia. The greatest amount of improvement in visual acuity was seen in simple myopes and the least in simple hyperopes. Compliance is critical for successful treatment of amblyopia.

  • 26. Elsner, Ann E.
    et al.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Gast, Thomas J.
    Muller, Matthew S.
    Litvin, Taras V.
    Ozawa, Glen Y.
    Cuadros, Jorge
    Underserved diabetic patients with refractive errors insufficient to lead to seeking eyecare2015Conference paper (Refereed)
    Abstract [en]

    Purpose: The increase in prevalence of diabetes is anticipated to increase the numbers of patients needing eye examinations. For our Phase II SBIR data, we reported that for > 2000 underserved diabetic patients in Alameda County, California, > 60% of patients reported no eye examination for at least 3 years despite that free photo diabetic retinopathy screenings were offered with follow on examination and eyecare. If eye screening for diabetic patients is not mandated, it becomes the responsibility of the patient or their primary care physician or endocrinologist to understand and act on the need for eye examinations. Methods: From the Alameda Health system of clinics, 197 diabetic patients agreed to be photoscreened for diabetic retinopathy. Our sample was enriched to have an increased probability of eye complications; thus, 26% had no apparent diabetic retinopathy; 38%, 17% and 4% had mild, moderate and severe non-proliferative diabetic retinopathy; and 13% had proliferative diabetic retinopathy. Of the 141 patients with diabetic retinopathy, 29% had bilateral CSME. Of the 132 diabetic patients (67 males and 65 females) returning for full eye exams, 52% were Hispanic, 21% African American, 14% Asian, and 8% NonHispanic Caucasian and Other, with an average age of 58.1 ± 9.4 years. Refractive errors were defined as spherical equivalent (SE) refraction, calculated as the spherical power plus one-half of the cylindrical power. Results: The overall mean spherical equivalent refraction M was −0.16 ± 1.50 D in the right eye (−6.0 D to +3.0 D) and +0.14 ± 1.35 D (−7.0 D to +4.0 D) in the left eye. Out of 132 patients, eight patients (6.1%) had visual acuity worse than 0.3 logMAR in both eyes. The right eyes of four patients and left eyes of eight patients had visual acuity worse than 0.3 logMAR, with fellow eyes having normal visual acuity. Conclusions: In a sample of largely minority, working age adults, there was very little refractive error and relatively good visual acuity when refracted, despite diabetic retinopathy or diabetic macular edema. Thus, working age diabetic patients may not regularly seek eye care for spectacle correction that would lead to the detection of diabetic retinopathy or diabetic macular edema.

  • 27.
    Green, Jason J. A.
    et al.
    Indiana University, USA.
    Elsner, Ann E.
    Indiana University, USA;Aeon Imaging, USA.
    Baskaran, Karthikeyan
    Indiana University, USA.
    Haggerty, Bryan P.
    Indiana University, USA.
    Clendenon, Jeff
    Aeon Imaging, USA.
    Muller, Matthew S.
    Aeon Imaging, USA.
    Retina Artery to Vein Intensity Ratio as a Function of Wavelength and Dark-Field Offset With Low Cost Ophthalmoscope2014Conference paper (Refereed)
    Abstract [en]

     PurposeTo quantify light return from retinal vessels for oxygenation status. To use a low-cost Digital Light Ophthalmoscope (DLO) based on a novel structured light pattern Digital Light Projector for quantitative retinal imaging.  MethodsFive normal subjects of ages 27-63 and various eye colors were imaged without mydriasis. The DLO produced a progressively scanning 6 pixel wide stripe, 96 stripe illumination pattern (85 μm stripe width at retina) with LEDs at 635 +/- 25nm (Red) and 535 +/- 70nm (Green) with a constant fixation target location across tests. The illumination was synchronized to a 13.2 Hz rolling shutter CMOS sensor (11 μm resolution at retina). To collect the light return from the retina at varying light multiply scattered levels, aperture offset was varied in position with respect to the illumination centerline: dark-field mode was obtained with large offsets and confocal mode had small offsets, where offset was varied from -517 μm (row start 30) to 1353 μm (row start 200). Multiple images of 12 bit dynamic range were captured in sequence, aligned with translational cross correlation, then time averaged to reduce noise. The artery and vein gray scale intensity level was measured at vessel centers for: 1) both vessels over background retina and 2) artery over the optic disc and vein over background. Mean-to-mean intensity ratios were then compared.  ResultsWith an aperture width of 704 μm, intensity varied by 2.60 bits (a factor of 4.5) for each subject per condition: red, green, artery, and vein, 3.39 bits if same subject and condition (2.3% Red A/V ratio CoV σ/μ), and by 5.07 bits over all tests. Yet, the ratio (Red/Green Artery)/(Red/Green Vein) was close to unity across offsets and linear fits had an R^2 regression of, for case 1: 0.72, 0.06, 0.25, 0.18, and 0.49, and case 2: 0.0005, 0.89, 0.75, 0.50, and 0.18. The Artery/Vein ratio trend slopes, intercept points, and inversions varied between subjects, i.e. contrast reversals were observed.  ConclusionsThe DLO can be utilized electronically to effectively perform quantitative fundus imaging at both Red and Green wavelengths, which is a step towards performing oximetry. 77 is zero offset

  • 28.
    Hernandez-Moreno, Laura
    et al.
    University of Minho Braga, Portugal.
    Moreno Perdomo, Natacha
    Hospital Santa Maria Maior E.P.E-Barcelos, Portugal.
    Aleman, Tomas S.
    University of Pennsylvania, USA.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Macedo, António Filipe
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry. University of Minho Braga, Portugal.
    Absent Foveal Pit, Also Known as Fovea Plana, in a Child without Associated Ocular or Systemic Findings2018In: Case Reports in Ophthalmological Medicine, ISSN 2090-6722, E-ISSN 2090-6730, p. 1-5, article id 2146826Article in journal (Refereed)
    Abstract [en]

    The purpose of this report is to describe a case of bilateral foveal hypoplasia in the absence of other ophthalmological or systemic manifestations. We characterize the case of a 9-year-old Caucasian male who underwent full ophthalmologic examination, including functional measures of vision and structural measurements of the eye. Best corrected visual acuity was 0.50 logMAR in the right eye and 0.40 logMAR in the left eye. Ophthalmoscopy revealed a lack of foveal reflex that was further investigated. Optical coherence tomography (OCT) confirmed the absence of foveal depression (pit). OCT images demonstrated the abnormal structure of retina in a region in which we expected a fovea; these findings were decisive to determine the cause of reduced acuity in the child.

  • 29.
    Ingling, Allen W
    et al.
    Aeon Imaging, USA.
    Muller, Matthew S
    Aeon Imaging, USA.
    Green, Jason J
    Indiana Univ, USA.
    Gast, Thomas
    Aeon Imaging, USA ; Indiana Univ, USA.
    Haggerty, Bryan
    Indiana Univ, USA.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry. Indiana Univ, USA.
    Clendenon, Jeffrey
    Aeon Imaging, USA.
    Stanfield, Kenneth A
    Aeon Imaging, USA.
    Elsner, Ann E
    Aeon Imaging, USA ; Indiana Univ, USA.
    Fixation stability readily obtained from confocal color fundus imaging2015In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 56, no 7, p. 515-515Article in journal (Refereed)
    Abstract [en]

    PurposeStabile fixation underpins most visual tasks such as reading, and is important for accurate assessment of visual function and treatment. Retinal imaging instruments average images over time to improve the signal to noise ratio, discarding useful eye movement data. We determined whether the frame-to-frame motion of the retina during non-mydriatic color fundus imaging could provide fixation stability measures, e.g. Bivariate Contour Ellipse Area (BCEA). MethodsNon-mydriatic color fundus images were acquired using the Digital Light Ophthalmoscope (DLO). Twenty subjects with varied fundus pigmentation were tested without mydriasis. The DLO uses a digital light projector with LED light sources to provide the illumination for both confocal imaging and fixation stimuli. The DLO projects a series of lines across the fundus that is synchronized to the 2D CMOS sensor, providing high contrast confocal imaging. Monochromatic 40 deg images were acquired with alternating red and green LED illumination at 14.3 Hz and overlayed to present a pseudo-color image to the operator in real time. To reduce pupil constriction and patient discomfort, the green LED was long-pass filtered with a 570 nm filter. A 1.5mm entrance pupil and time-averaged power of &lt;30 uW were used. Images were aligned automatically with custom software (MATLAB) using cross-correlation and 2D translation. A canvas of twice the image size was used to allow image alignment despite moderate eye movements. Blinks and large saccades were discarded and BCEA was computed. ResultsThe image alignment algorithm successfully aligned nearly all the frames, rejecting 3.7%, and allowing fixation stability to be computed from color fundus image data. The BCEA for 1 standard deviation was 2.97 log minarc2 for all subjects and both the red and yellow-orange illumination. There was no difference between the BCEA for red or yellow-orange illumination (t = .86). ConclusionsThe color DLO records sufficiently high quality images to reliably calculate measures of fixation stability. Despite recruiting an especially challenging population that included dark fundi, small pupils, high refractive errors, and media issues, we achieved success in all subjects tested to date.

  • 30.
    Kristiansson, Håkan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Lewis, Peter
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Rosén, Robert
    Biomedical and X-Ray Physics.
    Unsbo, Peter
    Biomedical and X-Ray Physics.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Effect of Optical Defocus on Peripheral Resolution Acuity in Old Healthy Emmetropes2011Conference paper (Refereed)
    Abstract [en]

    Background:

    A recent study by Rosén et al found peripheral low contrast resolution acuity, but not high contrast acuity, to be affected by defocus in young healthy eyes. Since aging causes considerable degradation in peripheral optics even in healthy subjects we wanted to see if, older subjects were also sensitive to defocus in low contrast acuity.

     

    Purpose:

    The aim of this study was to evaluate the effect of optical defocus on high and low contrast resolution acuity in the peripheral visual field of healthy older emmetropes.

     

    Subjects:

    High- and low-contrast resolution acuity was evaluated under spherical defocus in the 20° nasal visual field of four healthy older emmetropic subjects. The off-axis refractive error at the 20° nasal visual field was measured by a COAS-HD VR aberrometer and was corrected accordingly for each subject.

     

    Methods:

    Resolution thresholds for visual acuity (VA) were obtained using stimuli consisting of high- (100%) and low- (10%) contrast gratings that were presented on a CRT monitor situated 1.0 meter from the subject. Stimuli, 3° in diameter were presented for 300 ms using a 2AFC paradigm. Two repeated measurements, for both high and low contrast, were obtained for each point of defocus in 1.0 D steps up to ±4 D at 45mm vertex distance. The results are corrected to effective defocus at the corneal plane.

     

    Results:

    Defocus had no visible effect on high contrast VA, although there was a slight decrease in VA with higher amounts of positive defocus. However, defocus was found to have a significant effect on low contrast VA. Moreover, low contrast resolution was more sensitive to positive defocus than the negative defocus.

     

    Conclusions:

    Defocus has an impact on low contrast resolution whereas no such effect was found for high contrast resolution. These results are similar to those obtained by Rosén et al1 in young eyes. These results suggest that low contrast optotypes could possibly be used for determining subjective refraction in low vision subjects.

  • 31.
    Lewis, Peter
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Rosen, Robert
    Royal Institute of Technology KTH.
    Lundström, Linda
    Royal Institute of Technology KTH.
    Unsbo, Peter
    Royal Institute of Technology KTH.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Objectively Determined Refraction Improves Peripheral Vision2014In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 91, no 7, p. 740-746Article in journal (Refereed)
    Abstract [en]

    Purpose. The purpose of this study was twofold: to verify a fast, clinically applicable method for determining off-axis refraction and to assess the impact of objectively obtained off-axis refractive correction on peripheral low-contrast visual acuity. Methods. We measured peripheral low-contrast resolution acuity with Gabor patches both with and without off-axis correction at 20 degrees in the nasal visual field of 10 emmetropic subjects; the correction was obtained using a commercial open-field Hartmann-Shack wavefront sensor, the COAS-HD VR aberrometer. Off-axis refractive errors were calculated for a 5-mm circular pupil inscribed within the elliptical wavefront by COAS using the instruments' inbuilt "Seidel sphere" method. Results. Most of the subjects had simple myopic astigmatism, at 20 degrees in the nasal visual field ranging from -1.00 to -2.00 DC, with axis orientations generally near 90 degrees. The mean uncorrected and corrected low-contrast resolution acuities for all subjects were 0.92 and 0.86 logMAR, respectively (an improvement of 0.06 logMAR). For subjects with a scalar power refractive error of 1.00 diopters or more, the average improvement was 0.1 logMAR. The observed changes in low-contrast resolution acuity were strongly correlated with off-axis astigmatism (Pearson r = 0.95; p < 0.0001), the J(180) cross-cylinder component (Pearson r = 0.82; p = 0.0034), and power scalar (Pearson r = -0.75; p = 0.0126). Conclusions. The results suggest that there are definite benefits in correcting even moderate amounts of off-axis refractive errors; in this study, as little as -1.50 DC of off-axis astigmatism gave improvements of up to a line in visual acuity. It may be even more pertinent for people who rely on optimal peripheral visual function, specifically those with central visual field loss; the use of open-field aberrometers could be clinically useful in rapidly determining off-axis refractive errors specifically for this patient group who are generally more challenging to refract.

  • 32.
    Lewis, Peter
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Rosén, Robert
    Biomedical & X-Ray Physics.
    Unsbo, Peter
    Biomedical & X-Ray Physics.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Clinical Impact of Objectively Determined Peripheral Refractive Error Correction on Low-Contrast Resolution AcuityManuscript (preprint) (Other academic)
  • 33.
    Lewis, Peter
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Rosén, Robert
    KTH, Royal Institute of Technology, Stockholm, Sweden.
    Unsbo, Peter
    KTH, Royal Institute of Technology, Stockholm, Sweden.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    The Effect of Refractive-Correction on Peripheral Low-Contrast Resolution Acuity2012Conference paper (Other academic)
    Abstract [en]

    Purpose: High-contrast resolution acuity in the peripheral retina has been shown to be sampling-limited, however, a recent study indicates that peripheral low-contrast resolution acuity (PLCRA) is degraded by imposition of optical defocus. On the other hand, it has not been investigated whether refractive errors present in the peripheral field of normal, emmetropic eyes are sufficient to degrade PLCRA. The aim of this study was to evaluate the effect of peripheral refractive-correction on PLCRA in young emmetropes.Methods: Low-contrast (10 %) resolution acuity was measured off-axis (20° nasal visual field) on the right eyes of 10 emmetropic subjects (age 22 ± 2 years), both with and without peripheral refractive correction. Central and peripheral refractive errors were acquired using an open-field COAS-HD VR aberrometer. Stimuli, consisting of low-contrast Gabor patches with a visible diameter of 2°, were presented on a CRT monitor situated 3.0 meters from the subjects. Resolution thresholds were determined using a 2-alternative forced-choice Bayesian algorithm.Results: All the subjects had off-axis astigmatism (against-the-rule) at 20° in the nasal visual field ranging from -1.00 DC to -2.00 DC; of which four had -1.00 DC, three had -1.25 DC, one had -1.50 DC and the remaining two had -2.00 DC. Two of the subjects with -1.25 DC had -0.50 DS to -0.75 DS spherical errors; the rest had purely cylindrical errors. The mean uncorrected and corrected low-contrast resolution acuities for all subjects were 0.92 logMAR and 0.86 logMAR respectively. This shows an improvement in resolution acuity of 0.06 logMAR (p = 0.028) after correction of off-axis refractive errors. However when grouped according to the amount of astigmatism, the -1.00 DC group showed no difference in acuity with correction, the -1.25 DC, -1.50 DC and -2.00 DC groups improved on average by 0.05, 0.14 and 0.16 logMAR respectively.Conclusions: Correction of off-axis refractive errors had a positive effect on low-contrast resolution thresholds in the peripheral visual field on the emmetropic subjects in this study. Moreover, the effects become appreciable only for those subjects having larger degrees of astigmatism. This suggests that optical factors influence peripheral visual tasks involving low-contrast. There may be benefits in correcting even moderate amounts of off-axis refractive errors, especially for people who rely on optimal peripheral visual function.

  • 34.
    Lewis, Peter
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Holm, Victoria
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Dynamic Stimulus Presentation Facilitates Peripheral Resolution Acuity2013In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 54, article id e-abstract 574Article in journal (Other academic)
    Abstract [en]

    Purpose: Peripheral high-contrast resolution is sampling limited; the center to center spacing between ganglion cells ultimately limiting visual performance (Thibos et al., 1987). Although retinal image motion in the fovea has a detrimental effect on visual acuity, previous studies have suggested that retinal image motion may be advantageous in the peripheral visual field (Bex et al., 2003; Brown, 1972; Macedo et al., 2010). The aim of this study was to evaluate the effect of drift motion on peripheral resolution acuity.

    Methods: Peripheral high-contrast resolution acuity in a group of 26 subjects (age 23.5 ± 3.2 years) was initially determined using a 2-alternative forced-choice Bayesian algorithm; the threshold value defined as the spatial frequency resulting in a 75% correct response rate. The stimuli used to measure static visual acuity were stationary Gabor-patches with a visible diameter of 2° and were presented at 20° in the nasal visual field. We determined the percentage correct response rate for varying velocities using drifting Gabor patches of the same spatial frequency as determined during measurement of static visual acuity. The sine-wave gratings drifted within the Gaussian envelope at one of 10 angular velocities, varying from 0.2 to 2.0 degrees/second in 0.2 degrees/second steps.

    Results: Results showed an overall improvement in the subjects’ performance for all velocities. There was a significant difference in the percentage of correct responses between static stimulus presentation and for velocities of between 0.4 to 1.2 degrees/second (p < 0.05, One-way repeated measures ANOVA with Bonferroni post hoc tests). The average “correct response” for static stimulus presentation was 76 ± 2 %, improving to at least 85 % for velocities between 0.4 to 1.2 degrees/second. At velocities greater than 1.2 degrees/second performance was still better than for static stimulus presentation, but showed a gradual decline with increasing speed.

    Conclusions: In line with previous studies stimulus motion has a positive effect on peripheral high-contrast resolution acuity. Presenting moving stimuli may benefit patients who rely on peripheral visual function, such as those with central visual field loss subsequent to AMD.

  • 35. Lundström, L.
    et al.
    Rosén, R.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Jaeken, B.
    Gustafsson, Jörgen
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Artal, P.
    Unsbo, P.
    Symmetries in peripheral ocular aberrations2011In: Journal of Modern Optics, ISSN 0950-0340, E-ISSN 1362-3044, Vol. 58, no 19-20 SI, p. 1690-1695Article in journal (Refereed)
    Abstract [en]

    A mirror symmetry in the aberrations between the left and right eyes has previously been found foveally, but while a similar symmetry for the peripheral visual field is likely, it has not been investigated. Nevertheless, the peripheral optical quality is often evaluated in only one eye, because it is more time efficient than analyzing the whole visual field of both eyes. This study investigates the correctness of such an approach by measuring the peripheral wavefront aberrations in both eyes of 22 subjects out to +/- 40 degrees horizontally. The largest aberrations (defocus, astigmatism, and coma) were found to be significantly correlated between the left and right eyes when comparing the same temporal or nasal angle. The slope of the regression line was close to +/- 1 (within 0.05) for these aberrations, with a negative slope for the horizontally odd aberrations, i.e. the left and right eyes are mirror symmetric. These findings justify that the average result, sampled in one of the two eyes of many subjects, can be generalized to the other eye as well.

  • 36.
    Miranda, Antonio Miguel
    et al.
    University of Minho Braga, Portugal.
    Nunes-Pereira, Eduardo J
    University of Minho Braga, Portugal.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Macedo, António Filipe
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry. University of Minho Braga, Portugal.
    Eye movements, convergence distance and pupil-size when reading from smartphone, computer, print and tablet2018In: Scandinavian Journal of Optometry and Visual Science, ISSN 1891-0882, E-ISSN 1891-0890, Vol. 11, no 1, p. 1-5Article in journal (Refereed)
    Abstract [en]

    This study investigated the use of eye-tracking glasses to monitor visual behaviour when reading from electronic devices and paper in free-viewing conditions. The Tobii-Pro-Glasses were used to monitor 20 subjects with normal vision during reading tasks. Reading was performed in a smartphone, computer, paper and tablet. Texts from the IReST-test were read in devices in a random order. Participants read one text in each device and then repeated the same task 1 hour later; in total each participant read eight different texts. The sequence for the devices was randomized. We found differences between devices for saccade amplitude, fixation duration, convergence distance and pupil size. Reading speed between computer and tablet was slightly different (8 words-per-minute) and pupil size reduced up to 20% in electronic devices compared to print. Behavioural changes observed whilst reading from different devices may reflect an attempt from readers to optimize performance. The need to maintain visual performance under different visual condition may lead to increased visual symptoms. Eye-tracking glasses could be a valuable tool to investigate visual aspects of digital strain.

  • 37.
    Muller, Matthew S.
    et al.
    Aeon Imaging, USA.
    Elsner, Ann E.
    Aeon Imaging, USA;Indiana University, USA.
    Baskaran, Karthikeyan
    Indiana University, USA.
    Kollbaum, Elli J.
    Indiana University, USA.
    Petrig, Benno L.
    Aeon Imaging, USA.
    Real-Time Retinal Imaging with Integrated Visual Function Testing Using the Digital Light Ophthalmoscope2014In: IOVS, Orlando, Florida, USA, 2014, Vol. 55(13)Conference paper (Refereed)
    Abstract [en]

    Abstract Purpose: To perform low cost fixation stability assessment and kinetic perimetry during live fundus viewing using the Digital Light Ophthalmoscope (DLO). Methods: Kinetic perimetry was performed on 12 undilated normal subjects aged 25 - 63 with real-time confocal retinal imaging using the DLO. Having similar functionality to a Scanning Laser Ophthalmoscope, but at far lower cost, the DLO uses a single digital light projector to provide both the illumination for confocal imaging, and the stimuli for visual function measurements. Confocal retinal imaging is performed at 20 Hz with a 35.1 deg field of view. The imaging illumination is provided by a red 630 nm LED, with 40 µW time-averaged power at the cornea. Stimuli are shown in black over the red imaging illumination and are operator controlled in shape and position in real-time. The black stimuli are easily seen by the subject and are also clearly visible on the live view of the fundus. Subjects were instructed to stare at a fixation target while a Goldman V size (1.72 deg diameter) target was presented near the optic nerve head. The path taken by the stimulus was guided by one of eight meridians that converged at a point on the optic nerve head. The meridians were equally separated by 45 deg, and 7 deg long. Each stimulus moved incrementally outwards, from “not seen” to “seen”, at approximately 2.5 deg per sec. Once the stimulus was seen by the subject, an 8 image frame buffer was saved. Fixation stability was separately measured by acquiring 60 frames over 3 sec while the subject fixated on a cross-hair target with 0.3 deg line thickness. Results: The stimuli were directly visible on the retinal image frames, providing precise visual function testing. The visual function maps, formed by registering and superimposing the fundus images obtained for each stimulus meridian path, agreed well with the boundaries of the optic nerve head. The subjects’ fixation was 0.25±0.13 deg, measured over a 2 sec blink-free interval of the 3 sec acquisition. Conclusions: The DLO with integrated visual function testing is a flexible and cost-effective platform for conducting image-corrected visual function tests, such as kinetic perimetry and fixation stability assessment, and can be readily extended to scotoma mapping and reading tests.

  • 38. Muller, Matthew S
    et al.
    Gast, Thomas
    Clendenon, Jeffrey
    Ingling, Allen W
    Stanfield, Kenneth A
    Green, Jason J
    Baskaran, Karthikeyan
    Indiana University School of Optometry, USA.
    Haggerty, Bryan
    Peabody, Todd
    Elsner, Ann E
    Non-mydriatic color fundus imaging with the Digital Light Ophthalmoscope2015Conference paper (Refereed)
    Abstract [en]

    Purpose To provide non-mydriatic confocal color fundus imaging of sufficient quality for screening for diabetic retinopathy despite dark fundus pigmentation, small pupil, high refractive error, or other anterior segment issues. MethodsNon-mydriatic color fundus images of 34 volunteers (aged 39.2 ± 13.2 yr) were acquired using the Digital Light Ophthalmoscope (DLO). 10 subjects had dark fundi and/or high refractive errors, as well as other anterior segment issues. Unique to retinal cameras, the Digital Light Ophthalmoscope (DLO) uses a digital light projector with LED light sources to provide the illumination for both confocal imaging and fixation stimuli. The DLO projects a series of lines across the fundus that is synchronized to the electronic rolling shutter read-out on a 2D CMOS sensor, providing high contrast confocal imaging that is highly customizable through software. Monochromatic 40 deg field images were acquired with alternating red and green LED illumination at 14.3 Hz and overlayed to present a pseudo-color image to the operator in real time. To reduce pupil constriction and patient discomfort while maintaining strong blood absorption, the green illumination was long-pass filtered with a 570 nm filter, and a 1.5mm entrance pupil and time-averaged power of &lt;30 uW was used. ResultsThe DLO provided gradable quality non-mydriatic fundus images in all tested subjects, including those with dark fundi or pupils &lt; 2 mm, as judged by an EyePACS certified grader. The use of long pass filters in the green LED permitted high contrast, non-mydriatic images with illumination wavelengths &gt;570 nm and limited pupil constriction. Retinal vessels at the 4th branch or smaller, as well as neovascularization in diabetic retinopathy, could be seen. Hyperpigmentation was clearly seen both peripherally as bear tracks and centrally at the posterior pole. The aperture width and color balance can be adjusted to provide high contrast and yet relatively uniform and natural color across the image. ConclusionsThe DLO provides confocal color fundus images in real time without the use of short (&lt; 570nm) wavelength light. Despite recruiting an especially challenging population that included dark fundi, small pupils, high refractive errors, and media issues, we achieved a 100% success rate in obtaining gradable images for screening.

  • 39.
    Muller, Matthew S.
    et al.
    Aeon Imaging, USA.
    Green, Jason J.
    Indiana University, USA.
    Baskaran, Karthikeyan
    Indiana University, USA.
    Ingling, Allen W.
    Aeon Imaging, USA.
    Clendenon, Jeffrey L.
    Aeon Imaging, USA.
    Gast, Thomas J.
    Aeon Imaging, USA.
    Elsner, Ann E.
    Indiana University, USA.
    Non-mydriatic confocal retinal imaging using a digital light projector2015In: Proceedings of SPIE, vol 9376: Emerging Digital Micromirror Device Based Systems and Applications VII, 93760E / [ed] Michael R. Douglass; Philip S. King; Benjamin L. Lee, SPIE - International Society for Optical Engineering, 2015, p. 93760E-1-93760E-10Conference paper (Refereed)
    Abstract [en]

    A digital light projector is implemented as an integrated illumination source and scanning element in a confocal nonmydriatic retinal camera, the Digital Light Ophthalmoscope (DLO). To simulate scanning, a series of illumination lines are rapidly projected on the retina. The backscattered light is imaged onto a 2-dimensional rolling shutter CMOS sensor. By temporally and spatially overlapping the illumination lines with the rolling shutter, confocal imaging is achieved. This approach enables a low cost, flexible, and robust design with a small footprint. The 3rd generation DLO technical design is presented, using a DLP LightCrafter 4500 and USB3.0 CMOS sensor. Specific improvements over previous work include the use of yellow illumination, filtered from the broad green LED spectrum, to obtain strong blood absorption and high contrast images while reducing pupil constriction and patient discomfort.

  • 40.
    Nadeem Akram, Muhammad
    et al.
    University College of Southeast Norway, Norway.
    Baraas, Rigmor C.
    University College of Southeast Norway, Norway.
    Gilson, Stuart
    University College of Southeast Norway, Norway.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Accurate Wide-field Emmetropic Human Eye Model Based On Ocular Wavefront Measurements2017Conference paper (Refereed)
    Abstract [en]

    Purpose: To develop accurate wide-field eye model that reproduces the wavefront aberration of emmetropic eye. To demonstrate the ability to develop individual eye models based on the newly developed generic eye model. Methods: A high resolution Shack-Hartmann wavefront sensor is employed to measure the wavefront error from 40 deg Nasal to 40deg Temporal field and up to 20deg Inferior field of view in steps of 10deg of thirty young emmetropic subjects. Zernike polynomials up to 6th order are fitted to the measured wavefront over a circular exit pupil diameter of 4 mm. A mean wavefront is constructed for each field angle from the measured data set. A lens design program is used to reconstruct an model-eye that reproduces same wavefront as the mean wavefront of the measured data set over each field angle. Anatomical parameters range limits as well as dispersion of the eye (cornea, aqueous, lens and vitreous regions) is incorporated during model development to give a realistic eye model. Our model is different from previously published models in that it does not use Gradient index lens (GRIN) as the lens material simplifying optical modeling and ray tracing. In addition, the cornea and lens components are allowed to be tilted, decentered and rotated with respect to the optical axis to provide a much better fit to the measured set of wavefronts. Results: The RMS values, the wavefront shapes, Zernike coefficients and chromatic performance as predicted by the developed model closely match the measured values over the field of view. Our model does re-reproduce the Nasal-Temporal asymmetries found in the eye performance. Personalized eye models developed using the generic eye model also give excellent fit to the measured wavefront over the field of view. Conclusion: We believe our wide-field emmetropic eye model provides better ability to model peripheral vision. It can also be used for the design of advanced ophthalmic instruments, designing lenses for myopia control and low vision optical aids.

  • 41.
    Ozawa, Glen Y.
    et al.
    UC Berkeley School of Optometry, USA.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry. Indiana University, USA.
    Litvin, Taras V.
    UC Berkeley School of Optometry, USA.
    Elsner, Ann E.
    Indiana University, USA.
    Cuadros, Jorge
    UC Berkeley School of Optometry, USA.
    Clark, Christopher Anderson
    Indiana University, USA.
    Brahm, Shane
    Indiana University, USA.
    Young, Stuart B.
    Indiana University, USA.
    Robinson, Christina M.
    Indiana University, USA.
    Muller, Matthew S.
    AEON Imaging, USA.
    Central macular thickness of diabetic eyes with and without exudates within one disc diameter of the foveola2014Conference paper (Refereed)
    Abstract [en]

    Abstract Purpose: In diabetic retinopathy screenings, exudates within 1 disc diameter (DD) of the foveola are routinely used as a surrogate marker for clinically significant macular edema (CSME). We compared central macular thickness of diabetic eyes, which in photos, had and did not have exudates within 1 DD of the foveola. Methods: Patients were recruited from a diabetic retinopathy screening program serving mainly minorities in Alameda County, CA. One eye from each of 200 diabetic patients with diabetes was selected: 100 cases (50 males and 50 females) had exudates within 1 DD of the foveola, and 100 gender-, age-, and ethnicity-matched control diabetics did not have exudates within 1 DD of the foveola. Central macular thickness was determined using the iVue SD-OCT (Optovue Inc, Fremont, CA). Immediately following the OCT, three overlapping fundus photographs of each eye were taken with a Canon Cr-DGi nonmydriatic camera (Tokyo, Japan). Photos were graded by two EyePACS certified graders in a blind manner. Sensitivity and specificity of retinal photos for CSME were determined using the OCT as a gold standard. A 3-way ANOVA was performed for gender, age group (&lt;55 years vs &gt;55 years), and case versus control. Results: Central macular thickness was significantly greater for eyes with exudates within 1DD of the foveola versus eyes without (261±54 vs 244±23 μm, p=0.002). Notably, central macular thickness was greater in eyes with exudates within 1 DD of the fovea compared to those without in only the males (275±54 vs 249±25 μm, p=0.003). In the females, the two groups did not differ (247±51 vs 237±19 μm, p=0.2). ANOVA analysis also showed that central macular thickness was significantly greater among the entire group of males compared to the females (262±45 vs 243±39 μm, p&lt;0.0001). Regardless of exudates, older patients (&gt;55 years) had significantly greater central macular thickness than younger patients (260±54 vs 245±39 μm, p=0.009). In this study, exudates within 1 DD of the foveola had a sensitivity and specificity of 96% (95% CI=90-99%) and 82% (73-88%) for CSME, respectively. Conclusions: This study suggests that the surrogate marker for CSME, exudates within 1 DD of the foveola, is associated with central macular thickening. This central macular thickening is significantly greater in males, but not in females. Thus, the surrogate marker for CSME may be more important in males than in females.

  • 42.
    Rodrigues, Clarinda
    et al.
    Linnaeus University, School of Business and Economics, Department of Marketing.
    Rodrigues, Paula
    Macedo, António Filipe
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Baskaran, Karthikeyan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.
    Eye tracking the impact of in-store sensory and price messages on visual attention and intended purchase behavior2018In: Presented at the 13th Global Brand Conference, Newcastle upon Tyne, UK, May 2-4, 2018, 2018Conference paper (Refereed)
  • 43.
    Sivaramakrishnan, V. C.
    et al.
    Medical Research Foundation, India.
    Baskaran, Karthikeyan
    Medical Research Foundation, India.
    Bharadwaj, S. R.
    University of California, USA.
    Influence of convergence on vertical fusional vergence amplitude2005In: American Journal of Ophthalmology, ISSN 0002-9394, E-ISSN 1879-1891, Vol. 139, no 3 Suppl., p. S46-, article id EY313Article in journal (Refereed)
    Abstract [en]

    Purpose: Deficiency in vertical fusional vergence amplitude (VFVA) is known to cause asthenopia and oculomotor imbalances. The measurement of VFVA however is confounded by its increase with convergence (Hara et al., 1998). A quantitative relationship between the two vergences is thus necessary to predict the VFVA at a given convergence angle. Here, we sought to derive such a relationship by measuring the VFVA at a range of convergence angles. Methods: 30 subjects (17–21 yrs) wearing red-green goggles fused a pair of red-green concentric circles projected on a computer monitor at a distance of 50 cms in a dark room. The horizontal and vertical separation between the red-green circles determined the convergence and vertical vergence demand respectively. The VFVA was measured at 8 equally spaced convergence demands ranging from 0.58° to 11.13°. The convergence demands were either systematically increased or randomly varied across different sessions. in each session, the convergence demand was kept constant while the vertical vergence demand was varied in steps of 0.03°. The maximum vertical vergence demand that could be fused determined the VFVA. Results: The subjects’ data was divided into four groups based on the range of convergence demands that could be fused. in all the groups, the VFVA increased linearly with the systematic increase in convergence demand (mean regression equation: y 0.15x 0.49). Randomizing the convergence demands did not show any significant change in this relationship (y0.12x 0.80). Conclusion: The VFVA increases linearly in the range of convergence demands tested. The linear regression equation derived could be used in a clinical setup to predict the VFVA at a given convergence angle

  • 44.
    Young, Stuart B.
    et al.
    Indiana University, USA.
    Baskaran, Karthikeyan
    Indiana University, USA.
    Elsner, Ann E.
    Indiana University, USA;Aeon Imaging, USA.
    Muller, Matthew S.
    Aeon Imaging, USA.
    Gast, Thomas J.
    Indiana University, USA.
    Malinovsky, Victor E.
    Indiana University, USA.
    Clark, Christopher A.
    Indiana University, USA.
    Brahm, Shane
    Indiana University, USA.
    Litvin, Taras V.
    University of California Berkeley, USA.
    Ozawa, Glen Y.
    University of California Berkeley, USA.
    Cuadros, Jorge
    University of California Berkeley, USA.
    Central Macular Thickness in Diabetic Patients: A Gender Based Analysis2014Conference paper (Refereed)
    Abstract [en]

    PURPOSE: To investigate gender differences in central macular thickness (CMT) in underserved diabetic patients who were judged to have clinically significant macular edema (CSME), using the criterion of hard exudates within 1500 microns of the fovea. METHODS: Using EyePACS certified graders, 142 of 2080 diabetic patients from Alameda County, CA, clinics, had CSME as judged from color fundus images (Canon CR6-45NM). Of the 2080 patients, 1784 were imaged with SD-OCT (iVUE). Graders then analyzed the SD-OCT images for hard exudates and macular edema, excluding subjects with poor fixation or other ocular conditions. From these data, 142 patients with CSME, 11 males had CMT >300 microns. The 11 females from the group with the greatest values of CMT were then compared for CMT, and mean age. A control group, diabetic patients without CSME, showed a 12-micron larger CMT for males, as compared with females. Thus, a one-tailed t-test was used to determine if the CMT for males with CSME also was greater than for females by 12 microns. We compared mean age, self-report of duration of diabetes, and HbA1c values between genders. RESULTS: Males with CSME had an average CMT of 377 microns, statistically greater than the 12 micron difference expected between genders, with females averaging 321 microns (p<0.05). There was no statistical significance in the mean age between genders 59.3 vs. 59.2 yr. (p>0.05) or the population HbA1c levels 9.5 vs. 9.3% for males and females (p>0.05), respectively. While females had slightly longer durations of diabetes, Chi square analysis also showed no significance between genders (p>0.05). In the OCT images, males had cysts that were larger and more numerous. CONCLUSIONS: In patients with CSME, males had greater CMT than females. This difference is not explained by differences in thickness with gender when CSME is not found, nor by age or duration of diabetes. Instead, the cystic changes in the retinas of males were more striking.

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