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Lewis, P., Venkataraman, A. P. & Lundström, L. (2018). Contrast sensitivity in eyes with central scotoma: effect of stimulus drift. Optometry and Vision Science, 95(4), 354-361
Open this publication in new window or tab >>Contrast sensitivity in eyes with central scotoma: effect of stimulus drift
2018 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 95, no 4, p. 354-361Article in journal (Refereed) Published
Abstract [en]

Significance

In the field of visual rehabilitation of patients with central visual field loss, knowledge on how peripheral visual function can be improved is essential. This study presents measurements of peripheral dynamic contrast sensitivity (with optical correction) for off-axis viewing angles in subjects with central visual field loss.

Purpose

Subjects with central visual field loss (CFL) rely on a peripheral preferred retinal locus (PRL) for many visual tasks. It is therefore important to ascertain that contrast sensitivity (CS) is maximized in the PRL. This study evaluates the effect of stimulus motion, in combination with optical correction, on CS in subjects with CFL.

Methods

The off-axis refractive errors in the PRL of five young CFL subjects were measured with a COAS open-view Hartmann-Shack aberrometer. Low-contrast (25% and 10%) and high-contrast resolution acuity for stationary gratings was assessed with and without optical correction. High-contrast resolution was also measured for gratings drifting at 7.5 Hz (within a fixed Gaussian window). Furthermore, resolution CS was evaluated for both stationary and moving gratings with optical correction for a total of 2-3 spatial frequencies per subject.

Results

High-contrast resolution acuity was relatively insensitive to stimulus drift motion of 7.5 Hz, whereas CS for gratings of 0.5 cycles per degree improved with drift for all subjects. Furthermore, both high- and low-contrast static resolution improved with optical correction.

Conclusions

Just as for heathy eyes, stimulus motion of 7.5 Hz enhances CS for gratings of low spatial frequency also in the PRL of eyes with CFL. Concurrently, high contrast resolution is unaffected by the 7.5 Hz drift, but improves with off-axis optical correction. This highlights the importance of providing optimal refractive correction for subjects with CFL, and that stimulus motion can be used to further enhance CS at low spatial frequencies.

Place, publisher, year, edition, pages
Wolters Kluwer, 2018
Keywords
Central scotoma, Central visual field loss, Contrast sensitivity, Off-axis refractive errors, Peripheral vision, Spatiotemporal contrast sensitivity, Stimulus drift, Preferred retinal locus
National Category
Other Medical Sciences not elsewhere specified
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-71797 (URN)10.1097/OPX.0000000000001195 (DOI)000431181500011 ()29561506 (PubMedID)2-s2.0-85044854646 (Scopus ID)
Funder
Swedish Research Council, 621-2011-4094
Note

This research was also supported by “Berit and Carl-Johan Wettergrens Foundation.”

Available from: 2018-03-26 Created: 2018-03-26 Last updated: 2019-08-29Bibliographically approved
Santos, D., Abrantes, J., Lewis, P. & Macedo, A. F. (2018). Influence of the use of cane on the gait cycle of individuals who are blind. The British Journal of Visual Impairment, 36(3), 251-261
Open this publication in new window or tab >>Influence of the use of cane on the gait cycle of individuals who are blind
2018 (English)In: The British Journal of Visual Impairment, ISSN 0264-6196, E-ISSN 1744-5809, Vol. 36, no 3, p. 251-261Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to perform a biomechanical characterization of the gait cycle in individuals who are blind. Five individuals with ages between 16 and 19 years participated in this study. The task consisted of walks of 12m measured in two conditions: (1) with cane and (2) wihtout cane; a total of 20 walks in each condition were performed. During walks, participants were monitored with a Vicon 3D-motion capture system. Spatialtemporal, kinematic, kinetic, and dynamic parameters were recorded and compared between the two conditions. We observed an interaction between the condition and ankle angular measures (p = .003); the interaction was due to differences induced by condition in instants ‘opposite toe off’ (p = .045) and ‘opposite initial contact’ (p = .019). We also obtained a significant difference in the negative ankle-joint-power measures between conditions (p = .044). This study showed that the use of cane changes the gait pattern in individuals who are blind. The subtle changes in ankle behaviour when walking with a cane, compared with no cane, suggest better application of the force during the initial stages of support leading to a more comfortable gait. This type of assessment of gait may be important to improve mobility training and rehabilitation strategies.

Place, publisher, year, edition, pages
Sage Publications, 2018
Keywords
Biomechanics, cane, gait, orientation and mobility, impaired vision, blind
National Category
Sport and Fitness Sciences Ophthalmology
Research subject
Natural Science, Optometry; Social Sciences, Sport Science
Identifiers
urn:nbn:se:lnu:diva-76363 (URN)10.1177/0264619618782576 (DOI)000445236600007 ()
Available from: 2018-06-25 Created: 2018-06-25 Last updated: 2019-01-16Bibliographically approved
Moreno, L. H., Perdomo, N. M., Lima Ramos, P., Lewis, P., Linhares, J., Senra, H., . . . Macedo, A. F. (2018). Visual and psychological outcomes in patients with and without low vision diagnosed with similar eye diseases - initial results.. Paper presented at Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), APR 29-MAY 03, 2018, Honolulu, HI. Investigative Ophthalmology and Visual Science, 59(9)
Open this publication in new window or tab >>Visual and psychological outcomes in patients with and without low vision diagnosed with similar eye diseases - initial results.
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2018 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 59, no 9Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2018
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-78426 (URN)000442932800279 ()
Conference
Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), APR 29-MAY 03, 2018, Honolulu, HI
Available from: 2018-10-22 Created: 2018-10-22 Last updated: 2018-10-22Bibliographically approved
Venkataraman, A. P., Lewis, P., Unsbo, P. & Lundström, L. (2017). Peripheral resolution and contrast sensitivity: Effects of stimulus drift. Vision Research, 133, 145-149
Open this publication in new window or tab >>Peripheral resolution and contrast sensitivity: Effects of stimulus drift
2017 (English)In: Vision Research, ISSN 0042-6989, E-ISSN 1878-5646, Vol. 133, p. 145-149Article in journal (Refereed) Published
Abstract [en]

Optimal temporal modulation of the stimulus can improve foveal contrast sensitivity. This studyevaluates the characteristics oftheperipheral spatiotemporal contrast sensitivity function in normal-sighted subjects.The purpose is to identify a temporal modulation that can potentially improve the remaining peripheral visual function in subjects with central visual field loss. High contrast resolution cut-off for grating stimuli with four temporal frequencies (0, 5, 10 and 15 Hz drift) was first evaluated in the 10° nasal visual field.Resolution contrast sensitivity for all temporal frequencies was then measured at four spatial frequencies between 0.5 cycles per degree (cpd) and the measured stationary cut-off. All measurements were performed with eccentric optical correction. Similar to foveal vision, peripheral contrast sensitivity is highest for a combination of low spatial frequency and 5 to 10 Hz drift. At higher spatial frequencies, there was a decrease in contrast sensitivity with 15 Hz drift.Despitethis decrease, the resolution cut-off did not vary largely between the different temporal frequencies tested. ​ Additional measurements of contrast sensitivity at 0.5 cpd and resolution cut-off for stationary (0 Hz) and 7.5 Hz stimuli performed at 10, 15, 20 and 25° in the nasal visual field also showed the same characteristics across eccentricities.

Place, publisher, year, edition, pages
Pergamon Press, 2017
Keywords
Contrast sensitivity, Drifting gratings, Peripheral vision, Spatial frequency, Temporal frequency
National Category
Other Medical Sciences not elsewhere specified
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-61277 (URN)10.1016/j.visres.2017.02.002 (DOI)000399865500015 ()28268102 (PubMedID)2-s2.0-85015676927 (Scopus ID)
Funder
Swedish Research Council, 621-2011-4094
Available from: 2017-03-10 Created: 2017-03-10 Last updated: 2019-08-29Bibliographically approved
Lewis, P. (2016). Improving Peripheral Vision Through Optical Correction and Stimulus Motion. (Doctoral dissertation). Växjö: Linnaeus University Press
Open this publication in new window or tab >>Improving Peripheral Vision Through Optical Correction and Stimulus Motion
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The loss of central vision subsequent to macular disease is often extremely debilitating. People with central field loss (CFL) must use other peripheral areas of the retina in order to see; areas with inferior resolution capacity, which are also affected by off-axis optical errors. The overall aim of the work encompassed by this thesis was to identify and evaluate methods of improving vision for people with CFL; with focus on the effects of off-axis optical correction and stimulus motion on resolution acuity and contrast sensitivity.

Off-axis optical errors were measured using a commercially-available COAS-HD VR open-view aberrometer. We used adaptive psychophysical methods to evaluate grating resolution acuity and contrast sensitivity in the peripheral visual field; drifting gratings were employed to   measure the effect of motion on these two measures of visual performance. The effect of sphero-cylindrical correction and stimulus motion on visual performance in healthy eyes and in subjects with CFL was also studied; in addition, the effect of adaptive optics aberration correction was examined in one subject with CFL.

The COAS-HD aberrometer provided rapid and reliable measurements of off-axis refractive errors. Correction of these errors gave improvements in low-contrast resolution acuity in subjects with higher amounts of oblique astigmatism. Optical correction also improved high-contrast resolution acuity in most subjects with CFL, but not for healthy subjects. Adaptive optics correction improved both high and low contrast resolution acuity in the preferred retinal locus of a subject with CFL. The effect of stimulus motion depended on spatial frequency; motion of 7.5 Hz improved contrast sensitivity for stimuli of low spatial frequency in healthy and CFL subjects. Motion of 15 Hz had little effect on contrast sensitivity for low spatial frequency but resulted in reduced contrast sensitivity for higher spatial frequencies in healthy subjects. Finally, high-contrast resolution acuity was relatively insensitive to stimulus motion in the periphery.

This thesis has served to broaden the knowledge regarding peripheral optical errors, stimulus motion and their effects on visual function, both in healthy subjects and in people with CFL. Overall it has shown that correction of off-axis refractive errors is important for optimizing peripheral vision in subjects with CFL; the use of an open-view aberrometer simplifies the determination of these errors. In addition, moderate stimulus motion can have a beneficial effect on contrast sensitivity for objects of predominantly low spatial frequency.

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2016. p. 172
Series
Linnaeus University Dissertations ; 248/2016
Keywords
absolute central scotoma, central visual field loss, eccentric viewing, preferred retinal locus, open-view aberrometer, off-axis refractive errors, eccentric correction, dynamic visual acuity, spatial contrast sensitivity, temporal contrast sensitivity, spatio-temporal contrast sensitivity
National Category
Other Medical Sciences not elsewhere specified
Research subject
Natural Science, Optometry; Natural Science, Biomedical Sciences
Identifiers
urn:nbn:se:lnu:diva-52286 (URN)978-91-88357-14-4 (ISBN)
Public defence
2016-05-19, N2007, Smålandsgatan 26E, Kalmar, 09:45 (English)
Opponent
Supervisors
Available from: 2016-05-13 Created: 2016-04-28 Last updated: 2017-01-27Bibliographically approved
Venkataraman, A. P., Lewis, P. & Lundström, L. (2016). Optical Correction and Stimulus Motion to Improve Vision in Eccentric Preferred Retinal Locus. Paper presented at Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), MAY 01-05, 2016, Seattle, WA. Investigative Ophthalmology and Visual Science, 57(12), Article ID Meeting Abstract: 5175.
Open this publication in new window or tab >>Optical Correction and Stimulus Motion to Improve Vision in Eccentric Preferred Retinal Locus
2016 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 57, no 12, article id Meeting Abstract: 5175Article in journal, Meeting abstract (Refereed) Published
Place, publisher, year, edition, pages
ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2016
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-61689 (URN)000394210600080 ()
Conference
Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), MAY 01-05, 2016, Seattle, WA
Available from: 2017-03-24 Created: 2017-03-24 Last updated: 2017-11-29Bibliographically approved
Lundström, L., Venkataraman, A. P., Lewis, P. & Unsbo, P. (2016). Spatiotemporal contrast sensitivity in the 10 degrees visual field. Paper presented at Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), MAY 01-05, 2016, Seattle, WA. Investigative Ophthalmology and Visual Science, 57(12)
Open this publication in new window or tab >>Spatiotemporal contrast sensitivity in the 10 degrees visual field
2016 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 57, no 12Article in journal, Meeting abstract (Refereed) Published
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-61688 (URN)000394210603361 ()
Conference
Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), MAY 01-05, 2016, Seattle, WA
Available from: 2017-03-24 Created: 2017-03-24 Last updated: 2017-11-29Bibliographically approved
Lewis, P., Baskaran, K., Rosen, R., Lundström, L., Unsbo, P. & Gustafsson, J. (2014). Objectively Determined Refraction Improves Peripheral Vision. Optometry and Vision Science, 91(7), 740-746
Open this publication in new window or tab >>Objectively Determined Refraction Improves Peripheral Vision
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2014 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 91, no 7, p. 740-746Article in journal (Refereed) Published
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.

Keywords
visual acuity, low-contrast resolution acuity, off-axis refractive errors, peripheral vision, off-axis astigmatism, macular degeneration, AMD
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-36833 (URN)10.1097/OPX.0000000000000301 (DOI)000338778400010 ()2-s2.0-84903754538 (Scopus ID)
Available from: 2014-09-10 Created: 2014-09-10 Last updated: 2017-12-05Bibliographically approved
Lewis, P., Holm, V., Baskaran, K. & Gustafsson, J. (2013). Dynamic Stimulus Presentation Facilitates Peripheral Resolution Acuity. Paper presented at ARVO 2013, Life-changing research, Seattle, Wash., May 5 – 9, 2013. Investigative Ophthalmology and Visual Science, 54, Article ID e-abstract 574.
Open this publication in new window or tab >>Dynamic Stimulus Presentation Facilitates Peripheral Resolution Acuity
2013 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 54, article id e-abstract 574Article in journal, Meeting abstract (Other academic) Published
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.

Keywords
Dynamic, visual, acuity
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-30839 (URN)
Conference
ARVO 2013, Life-changing research, Seattle, Wash., May 5 – 9, 2013
Available from: 2013-12-02 Created: 2013-12-02 Last updated: 2017-12-06Bibliographically approved
Baskaran, K., Rosen, R., Lewis, P., Unsbo, P. & Gustafsson, J. (2012). Benefit of Adaptive Optics Aberration Correction at Preferred Retinal Locus. Optometry and Vision Science, 89(9), 1417-1423
Open this publication in new window or tab >>Benefit of Adaptive Optics Aberration Correction at Preferred Retinal Locus
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2012 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 89, no 9, p. 1417-1423Article in journal (Refereed) Published
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

Keywords
REFRACTIVE ERROR, RESOLUTION ACUITY, VISION
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-21527 (URN)10.1097/OPX.0b013e318264f2a7 (DOI)22842306 (PubMedID)2-s2.0-84865730607 (Scopus ID)
Available from: 2012-09-05 Created: 2012-09-05 Last updated: 2017-12-07Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8365-0601

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