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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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- 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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| 7. |
- Venkataraman, Abinaya Priya, 1985-, et al.
(författare)
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Peripheral resolution and contrast sensitivity : effects of monochromatic and chromatic aberrations
- 2019
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Ingår i: Optical Society of America. Journal A. - : Optical Society of America. - 1084-7529 .- 1520-8532. ; 36:4, s. B52-B57
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Tidskriftsartikel (refereegranskat)abstract
- Correction and manipulation of peripheral refractive errors are indispensable for people with central vision loss and in optical interventions for myopia control. This study investigates further enhancements of peripheral vision by compensating for monochromatic higher-order aberrations (with an adaptive optics system) and chromatic aberrations (with a narrowband green filter, 550 nm) in the 20 degrees nasal visual field. Both high-contrast detection cutoff and contrast sensitivity improved with optical correction. This improvement was most evident for gratings oriented perpendicular to the meridian due to asymmetric optical errors. When the natural monochromatic higher-order aberrations are large, resolution of 10% contrast oblique gratings can also be improved with correction of these errors. Though peripheral vision is mainly limited by refractive errors and neural factors, higher-order aberration correction beyond conventional refractive errors can still improve peripheral vision under certain circumstances.
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| 8. |
- Venkataraman, Abinaya Priya, 1985-, et al.
(författare)
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Peripheral vision and hazard detection with average phakic and pseudophakic optical errors
- 2021
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Ingår i: Biomedical Optics Express. - : The Optical Society. - 2156-7085. ; 12:6, s. 3082-3090
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Tidskriftsartikel (refereegranskat)abstract
- Intraocular lens (IOL) implantation following cataract extraction is the most common ophthalmic surgical procedure across the world. The IOL designs are constantly evolving and the postoperative visual outcomes are also improving significantly [1-3]. However, these reported outcomes are measured mainly for the central vision. Similar to other forms of vision correction such as spectacle lenses and contact lenses, IOLs are also designed to provide optimal image quality in the central visual field. Both theoretical and experimental evidence suggest that the peripheral optical errors are larger in eyes implanted with spherical and aspherical monofocal IOLs than phakic eyes [4-7]. Tabernero et al., reported an increase in the peripheral optical errors by analysing eyes that were implanted with monofocal IOLs from a variety of manufacturing companies and different optical designs, both spherical and aspherical [4]. The gradient index of the crystalline lens in the phakic eyes is suggested to partly compensate for the peripheral corneal astigmatism and the replacement of the crystalline lens with an IOL of constant index therefore results in higher The impact of peripheral optical errors induced by intraocular lenses was evaluated by simulating the average phakic and pseudophakic image qualities. An adaptive optics system was used to simulate the optical errors in 20 degrees nasal and inferior visual field in phakic subjects. Peripheral resolution acuity, contrast sensitivity and hazard detection were evaluated. Pseudophakic errors typical for monofocal designs had a negative effect on resolution acuity and contrast sensitivity and the hazard detection task also showed increased false positive and misses and a longer reaction time compared to phakic optical errors. The induced peripheral pseudophakic optical errors affect the peripheral visual performance and thereby impact functional vision.
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- Venkataraman, Abinaya Priya, 1985-
(författare)
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Vision Beyond the Fovea: Evaluation and Stimuli Properties
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This research is about evaluating vision in the periphery. Peripheral vision is of fundamental importance in the performance of our everyday activities. The aim of this thesis is to develop methods suitable for the evaluation of peripheral vision and to assess how different visual functions vary across the visual field. The results have application both within the field of visual rehabilitation of people with central visual field loss (CFL)and as well as in myopia research.All methods for assessing peripheral vision were implemented with adaptive psychophysical algorithms based on Bayesian statistics. A routine for time-efficient evaluation of peripheral contrast sensitivity was implemented and verified for measurements out to 30° in the visual field. Peripheral vision was evaluated for different properties of the stimuli: sharpness, motion, orientation, and extent. Optical quality was controlled using adaptive optics and/or corrective spectacles specially adapted for the peripheral viewing angle. We found that many peripheral visual functions improved with optical correction, especially in people with CFL. We also found improvements in peripheral contrast sensitivity for low spatial frequencies when stimuli drifted at 5 to 10 Hz; this applies both for people with normal vision and those with CFL. In the periphery, it is easier to see lines that are oriented parallel with respect to the visual field meridian. We have shown that this directional bias is present for both resolution and detection tasks in the periphery, even when the asymmetric optical errors are minimized. For accurate evaluation of peripheral vision, we therefore recommend using gratings that are oriented oblique to the visual field meridian. The directional bias may have implications in how peripheral image quality affects myopia progression. Another proof that peripheral vision can influence central visual function is the fact that, when the stimulus extent was increased beyond the fovea, the blur in the stimulus was less noticeable.
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