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Baskaran, Karthikeyan, Senior LecturerORCID iD iconorcid.org/0000-0002-3745-0035
Publikasjoner (10 av 43) Visa alla publikasjoner
Arthur, E., Young, S. B., Elsner, A. E., Baskaran, K., Papay, J. A., Muller, M. S., . . . Cuadros, J. A. (2019). Central Macular Thickness in Diabetic Patients: A Sex-based Analysis. Optometry and Vision Science, 96(4), 266-275
Åpne denne publikasjonen i ny fane eller vindu >>Central Macular Thickness in Diabetic Patients: A Sex-based Analysis
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2019 (engelsk)Inngår i: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 96, nr 4, s. 266-275Artikkel i tidsskrift (Fagfellevurdert) Published
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.

sted, utgiver, år, opplag, sider
American Academy of Optometry, 2019
HSV kategori
Forskningsprogram
Naturvetenskap, Optometri
Identifikatorer
urn:nbn:se:lnu:diva-81656 (URN)10.1097/OPX.0000000000001363 (DOI)000463198100005 ()30907864 (PubMedID)2-s2.0-85063866010 (Scopus ID)
Tilgjengelig fra: 2019-04-03 Laget: 2019-04-03 Sist oppdatert: 2019-08-29bibliografisk kontrollert
Baskaran, K., Macedo, A. F. & Calabrèse, A. (2019). Rater and algorithm data of maximum reading speed (MRS) and critical print size (CPS) of 101 low vision participants..
Åpne denne publikasjonen i ny fane eller vindu >>Rater and algorithm data of maximum reading speed (MRS) and critical print size (CPS) of 101 low vision participants.
2019 (engelsk)Dataset, Primärdata
HSV kategori
Forskningsprogram
Naturvetenskap, Optometri
Identifikatorer
urn:nbn:se:lnu:diva-82621 (URN)
Tilgjengelig fra: 2019-05-20 Laget: 2019-05-20 Sist oppdatert: 2019-05-22
Baskaran, K., Macedo, A. F., He, Y., Hernandez-Moreno, L., Queirós, T., Mansfield, J. S. & Calabrèse, A. (2019). Scoring reading parameters: An inter-rater reliability study using the MNREAD chart. PLoS ONE, 14(6), 1-14, Article ID e0216775.
Åpne denne publikasjonen i ny fane eller vindu >>Scoring reading parameters: An inter-rater reliability study using the MNREAD chart
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2019 (engelsk)Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 14, nr 6, s. 1-14, artikkel-id e0216775Artikkel i tidsskrift (Fagfellevurdert) Published
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.

sted, utgiver, år, opplag, sider
Public Library of Science, 2019
Emneord
MNREAD acuity chart, visual impairment, algorithms
HSV kategori
Forskningsprogram
Naturvetenskap, Optometri
Identifikatorer
urn:nbn:se:lnu:diva-84759 (URN)10.1371/journal.pone.0216775 (DOI)000470658500005 ()31173587 (PubMedID)2-s2.0-85067111247 (Scopus ID)
Tilgjengelig fra: 2019-06-08 Laget: 2019-06-08 Sist oppdatert: 2019-08-29bibliografisk kontrollert
Hernandez-Moreno, L., Moreno Perdomo, N., Aleman, T. S., Baskaran, K. & Macedo, A. F. (2018). Absent Foveal Pit, Also Known as Fovea Plana, in a Child without Associated Ocular or Systemic Findings. Case Reports in Ophthalmological Medicine, 1-5, Article ID 2146826.
Åpne denne publikasjonen i ny fane eller vindu >>Absent Foveal Pit, Also Known as Fovea Plana, in a Child without Associated Ocular or Systemic Findings
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2018 (engelsk)Inngår i: Case Reports in Ophthalmological Medicine, ISSN 2090-6722, E-ISSN 2090-6730, s. 1-5, artikkel-id 2146826Artikkel i tidsskrift (Fagfellevurdert) Published
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.

sted, utgiver, år, opplag, sider
Hindawi Publishing Corporation, 2018
HSV kategori
Forskningsprogram
Naturvetenskap, Optometri
Identifikatorer
urn:nbn:se:lnu:diva-77000 (URN)10.1155/2018/2146826 (DOI)000440906700001 ()30147974 (PubMedID)
Tilgjengelig fra: 2018-07-26 Laget: 2018-07-26 Sist oppdatert: 2019-02-27bibliografisk kontrollert
Miranda, A. M., Nunes-Pereira, E. J., Baskaran, K. & Macedo, A. F. (2018). Eye movements, convergence distance and pupil-size when reading from smartphone, computer, print and tablet. Scandinavian Journal of Optometry and Visual Science, 11(1), 1-5
Åpne denne publikasjonen i ny fane eller vindu >>Eye movements, convergence distance and pupil-size when reading from smartphone, computer, print and tablet
2018 (engelsk)Inngår i: Scandinavian Journal of Optometry and Visual Science, ISSN 1891-0882, E-ISSN 1891-0890, Vol. 11, nr 1, s. 1-5Artikkel i tidsskrift (Fagfellevurdert) Published
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.

sted, utgiver, år, opplag, sider
The Norwegian Association of Optometry, 2018
Emneord
Reading, Displays, Reading, Eye tracking glasses, Digital eye strain
HSV kategori
Forskningsprogram
Naturvetenskap, Optometri
Identifikatorer
urn:nbn:se:lnu:diva-77025 (URN)10.5384/SJOVS.vol11i1p1 (DOI)
Tilgjengelig fra: 2018-07-30 Laget: 2018-07-30 Sist oppdatert: 2018-11-07bibliografisk kontrollert
Rodrigues, C., Rodrigues, P., Macedo, A. F. & Baskaran, K. (2018). Eye tracking the impact of in-store sensory and price messages on visual attention and intended purchase behavior. In: Presented at the 13th Global Brand Conference, Newcastle upon Tyne, UK, May 2-4, 2018: . Paper presented at 13th Global Brand Conference, Newcastle upon Tyne, UK, May 2-4, 2018.
Åpne denne publikasjonen i ny fane eller vindu >>Eye tracking the impact of in-store sensory and price messages on visual attention and intended purchase behavior
2018 (engelsk)Inngår i: Presented at the 13th Global Brand Conference, Newcastle upon Tyne, UK, May 2-4, 2018, 2018Konferansepaper, Oral presentation only (Fagfellevurdert)
HSV kategori
Forskningsprogram
Ekonomi, Marknadsföring
Identifikatorer
urn:nbn:se:lnu:diva-74345 (URN)
Konferanse
13th Global Brand Conference, Newcastle upon Tyne, UK, May 2-4, 2018
Tilgjengelig fra: 2018-05-15 Laget: 2018-05-15 Sist oppdatert: 2018-12-05bibliografisk kontrollert
Akram, M. N., Baraas, R. C. & Baskaran, K. (2018). Improved wide-field emmetropic human eye model based on ocular wavefront measurements and geometry-independent gradient index lens. Optical Society of America. Journal A: Optics, Image Science, and Vision, 35(11), 1954-1967
Åpne denne publikasjonen i ny fane eller vindu >>Improved wide-field emmetropic human eye model based on ocular wavefront measurements and geometry-independent gradient index lens
2018 (engelsk)Inngår i: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 35, nr 11, s. 1954-1967Artikkel i tidsskrift (Fagfellevurdert) Published
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&#x00B0; nasal to 40&#x00B0; temporal and up to 20&#x00B0; inferior field). Anatomical parameters, asymmetries, and dispersion properties of the eye&#x2019;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.

sted, utgiver, år, opplag, sider
Optical Society of America, 2018
Emneord
Crystalline lens, Eye models, Gradient index lenses, Monochromatic aberrations, Refractive index, Visual optics
HSV kategori
Forskningsprogram
Naturvetenskap, Optometri
Identifikatorer
urn:nbn:se:lnu:diva-78543 (URN)10.1364/JOSAA.35.001954 (DOI)000448935600022 ()2-s2.0-85055896169 (Scopus ID)
Tilgjengelig fra: 2018-10-30 Laget: 2018-10-30 Sist oppdatert: 2019-08-29bibliografisk kontrollert
Nadeem Akram, M., Baraas, R. C., Gilson, S. & Baskaran, K. (2017). Accurate Wide-field Emmetropic Human Eye Model Based On Ocular Wavefront Measurements. In: : . Paper presented at 16th International Myopia Conference, 14-17 September 2017, Aston University, Birmingham, UK. , Article ID P 053.
Åpne denne publikasjonen i ny fane eller vindu >>Accurate Wide-field Emmetropic Human Eye Model Based On Ocular Wavefront Measurements
2017 (engelsk)Konferansepaper, Poster (with or without abstract) (Fagfellevurdert)
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.

HSV kategori
Forskningsprogram
Naturvetenskap, Optometri
Identifikatorer
urn:nbn:se:lnu:diva-74520 (URN)
Konferanse
16th International Myopia Conference, 14-17 September 2017, Aston University, Birmingham, UK
Tilgjengelig fra: 2018-05-24 Laget: 2018-05-24 Sist oppdatert: 2018-12-07bibliografisk kontrollert
Alhamami, M., Elsner, A., Malinovsky, V., Clark, C., Haggerty, B., Ozawa, G., . . . Miura, M. (2017). Comparison of Cysts in Red and Green Images for Diabetic Macular Edema. Optometry and Vision Science, 94(2), 137-149
Åpne denne publikasjonen i ny fane eller vindu >>Comparison of Cysts in Red and Green Images for Diabetic Macular Edema
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2017 (engelsk)Inngår i: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 94, nr 2, s. 137-149Artikkel i tidsskrift (Fagfellevurdert) Published
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.

Emneord
diabetic retinopathy, diabetic macular edema, clinically significant macular edema, retina imaging, light tissue interactions, cystoid macular edema, color fundus photography, diabetic retinal screening
HSV kategori
Forskningsprogram
Naturvetenskap, Optometri
Identifikatorer
urn:nbn:se:lnu:diva-58221 (URN)10.1097/OPX.0000000000001010 (DOI)
Tilgjengelig fra: 2016-11-20 Laget: 2016-11-20 Sist oppdatert: 2019-06-10bibliografisk kontrollert
Baskaran, K., Calabrèse, A., Castet, E., Moreno, L., Silva, M. & Macedo, A. F. (2017). Scoring reading parameters: an inter-rater reliability study using the MNREAD test. In: : . Paper presented at Vision 2017, 12th International Conference by the International Society for Low Vision Research and Rehabilitation (ISLRR), 25–29 June 2017, The Hague, The Netherlands.
Åpne denne publikasjonen i ny fane eller vindu >>Scoring reading parameters: an inter-rater reliability study using the MNREAD test
Vise andre…
2017 (engelsk)Konferansepaper, Oral presentation only (Fagfellevurdert)
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.

HSV kategori
Forskningsprogram
Naturvetenskap, Optometri
Identifikatorer
urn:nbn:se:lnu:diva-74469 (URN)
Konferanse
Vision 2017, 12th International Conference by the International Society for Low Vision Research and Rehabilitation (ISLRR), 25–29 June 2017, The Hague, The Netherlands
Tilgjengelig fra: 2018-05-22 Laget: 2018-05-22 Sist oppdatert: 2018-12-07bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0002-3745-0035