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- Lewis, Peter, 1971-, et al.
(författare)
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Contrast sensitivity in eyes with central scotoma : effect of stimulus drift
- 2018
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Ingår i: Optometry and Vision Science. - : Wolters Kluwer. - 1040-5488 .- 1538-9235. ; 95:4, s. 354-361
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Tidskriftsartikel (refereegranskat)abstract
- SignificanceIn 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.PurposeSubjects 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.MethodsThe 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.ResultsHigh-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.
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| 2. |
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| 3. |
- Lundström, Linda, et al.
(författare)
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Peripheral optical errors and hazard perception
- 2021
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Ingår i: Investigative Ophthalmology and Visual Science. - : Association for Research in Vision and Ophthalmology. - 0146-0404 .- 1552-5783. ; 62:8
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 4. |
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| 5. |
- Rosén, Robert, et al.
(författare)
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Quick contrast sensitivity measurements in the periphery
- 2014
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Ingår i: Journal of Vision. - : Association for Research in Vision and Ophthalmology (ARVO). - 1534-7362. ; 14:8
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Tidskriftsartikel (refereegranskat)abstract
- Measuring the contrast sensitivity function (CSF) in the periphery of the eye is complicated. The lengthy measurement time precludes all but the most determined subjects. The aim of this study was to implement and evaluate a faster routine based on the quick CSF method (qCSF) but adapted to work in the periphery. Additionally, normative data is presented on neurally limited peripheral CSFs. A peripheral qCSF measurement using 100 trials can be performed in 3 min. The precision and accuracy were tested for three subjects under different conditions (number of trials, peripheral angles, and optical corrections). The precision for estimates of contrast sensitivity at individual spatial frequencies was 0.07 log units when three qCSF measurements of 100 trials each were averaged. Accuracy was estimated by comparing the qCSF results with a more traditional measure of CSF. Average accuracy was 0.08 log units with no systematic error. In the second part of the study, we collected three CSFs of 100 trials for six persons in the 20 degrees nasal, temporal, inferior, and superior visual fields. The measurements were performed in an adaptive optics system running in a continuous closed loop. The Tukey HSD test showed significant differences (p < 0.05) between all fields except between the nasal and the temporal fields. Contrast sensitivity was higher in the horizontal fields, and the inferior field was better than the superior. This modified qCSF method decreases the measurement time significantly and allows otherwise unfeasible studies of the peripheral CSF.
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| 7. |
- Venkataraman, Abinaya Priya, et al.
(författare)
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Blur adaptation : Contrast sensitivity changes and stimulus extent
- 2015
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Ingår i: Vision Research. - : Elsevier. - 0042-6989 .- 1878-5646. ; 110:PA, s. 100-106
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Tidskriftsartikel (refereegranskat)abstract
- A prolonged exposure to foveal defocus is well known to affect the visual functions in the fovea. However, the effects of peripheral blur adaptation on foveal vision, or vice versa, are still unclear. In this study, we therefore examined the changes in contrast sensitivity function from baseline, following blur adaptation to small as well as laterally extended stimuli in four subjects. The small field stimulus (7.5° visual field) was a 30. min video of forest scenery projected on a screen and the large field stimulus consisted of 7-tiles of the 7.5° stimulus stacked horizontally. Both stimuli were used for adaptation with optical blur (+2.00. D trial lens) as well as for clear control conditions. After small field blur adaptation foveal contrast sensitivity improved in the mid spatial frequency region. However, these changes neither spread to the periphery nor occurred for the large field blur adaptation. To conclude, visual performance after adaptation is dependent on the lateral extent of the adaptation stimulus.
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| 8. |
- Venkataraman, Abinaya Priya, et al.
(författare)
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Choice of grating orientation for evaluation of peripheral vision
- 2016
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Ingår i: Optometry and Vision Science. - : Lippincott Williams & Wilkins. - 1040-5488 .- 1538-9235. ; 93:6, s. 567-574
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Peripheral resolution acuity depends on the orientation of the stimuli. However, it is uncertain if such a meridional effect also exists for peripheral detection tasks because they are affected by optical errors. Knowledge of the quantitative differences in acuity for different grating orientations is crucial for choosing the appropriate stimuli for evaluations of peripheral resolution and detection tasks. We assessed resolution and detection thresholds for different grating orientations in the peripheral visual field.Methods: Resolution and detection thresholds were evaluated for gratings of four different orientations in eight different visual field meridians in the 20-deg visual field in white light. Detection measurements in monochromatic light (543 nm; bandwidth, 10 nm) were also performed to evaluate the effects of chromatic aberration on the meridional effect. A combination of trial lenses and adaptive optics system was used to correct the monochromatic lower- and higher-order aberrations.Results: For both resolution and detection tasks, gratings parallel to the visual field meridian had better threshold compared with the perpendicular gratings, whereas the two oblique gratings had similar thresholds. The parallel and perpendicular grating acuity differences for resolution and detection tasks were 0.16 logMAR and 0.11 logMAD, respectively. Elimination of chromatic errors did not affect the meridional preference in detection acuity.Conclusions: Similar to peripheral resolution, detection also shows a meridional effect that appears to have a neural origin. The threshold difference seen for parallel and perpendicular gratings suggests the use of two oblique gratings as stimuli in alternative forced-choice procedures for peripheral vision evaluation to reduce measurement variation.
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| 10. |
- Venkataraman, Abinaya Priya, 1985-, et al.
(författare)
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Impact of peripheral optical errors in AMD and healthy eyes
- 2021
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Ingår i: Investigative Ophthalmology and Visual Science. - : ASSOC RESEARCH VISION OPHTHALMOLOGY INC. - 0146-0404 .- 1552-5783. ; 62:8
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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