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Joella Martire, Tiffany Arango, Peter J. Bex, Nicole C Ross; Visual performance at the PRL in monocular versus binocular viewing using simulated gaze-contingent scotomas. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2564. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The majority of low vision patients are affected by macular pathologies where foveal function is lost in both eyes and a preferred retinal locus (PRL) is adopted. Much research has explored properties and visual performance of the PRL in monocular viewing, but little is known about the PRL under more realistic binocular viewing conditions. We used simulated gaze-contingent independent scotomas in normally sighted participants to explore visual performance of the PRL under binocular and monocular viewing.
Gaze contingent scotomas (0.5, 1.0, 2.0 degree radius) were simulated in each eye of participants in monocular (n=12) and binocular (n=12) viewing conditions. Scotomas were updated at 120Hz refresh rate based on a 500Hz eye tracker. Size and location of binocular scotomas were independently controlled with active shutter glasses. Visual performance was assessed using contrast sensitivity function (CSF) and word identification. For CSF, observers identified band-pass filtered letters, and a quick algorithm controlled spatial frequency and contrast. For word identification, participants identified whether a word or non-word was presented and a quick algorithm controlled font size and duration. Outcomes were high-frequency CSF threshold (CSF acuity), area under the logCSF curve (AULCSF), threshold reading acuity and reading speed.
Under monocular viewing conditions, contrast sensitivity decreased with increasing scotoma size, with declining CSF acuity (p<0.01) and decreasing AULCSF (p <0.01). For word identification, under monocular conditions, there was no effect of scotoma size on reading acuity but a significant effect for maximum reading speed (p<0.01). Under binocular viewing conditions there was no significant effect of scotoma size on visual performance for any of the tasks. CSF acuity was significantly better when scotomas were symmetric than asymmetric (p=.01) across all sizes.
With simulated independent binocular gaze-contingent scotomas, visual performance at the PRL differs under monocular versus binocular viewing conditions. Performance depends on whether the scotomas are symmetric or asymmetric and the method used to assess visual function. The results stress the need for the development and use of binocular visual assessments to explore properties and visual performance of the PRL in low vision patients.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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