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Concetta F Alberti, Peter Bex; Do oculomotor adaptations to a volume scotoma provide functional benefits for binocular vision?. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4695.
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© ARVO (1962-2015); The Authors (2016-present)
Binocular eye movements can adjust the projection of a retinal volume scotoma (Arditi, 1988) and modify the retinal disparity of targets in depth. We recently showed (Alberti et al, ARVO 2015) that observers with gaze-contingent simulated independent scotomas make binocular eye movements that move the location of the volume scotoma. We assessed whether such adaptations improve binocular contrast sensitivity in the peripheral visual field.
The contrast sensitivity function was measured with a 26AFC task in which normally-sighted observers (N=6) identified bandpass filtered letters whose spatial frequency and contrast were varied with modified quickCSF algorithm (Lesmes et al, 2010). The letters were positioned 2° in the lower visual field and, in randomly interleaved trials, were either in corresponding retinal locations or displaced horizontally by ±0.25 letter widths to create near or far visual disparity. The gaze contingent scotoma in each eye was a Gaussian windowed (σ=0.5° OS and 1° OD) patch of pink noise, centered on the fovea. Dichoptic presentation of the stimuli was controlled with nVidia 3D glasses synched to a low-latency 144Hz display and eye tracking was measured at 1000Hz with an Eyelink II.
The area under the logCSF (AULCSF) was lower for positive or negative disparity stimuli than for stimuli at zero disparity (mean 1.55 vs 1.73, p<0.001), as was peak contrast sensitivity (mean 1.43 vs 1.61, p<0.001). CSF acuity (the highest spatial frequency letter identifiable at full contrast) and other parameters of the CSF did not significantly vary with disparity.
In the peripheral visual field, binocular contrast summation requires spatially aligned stimuli and does not occur for disparity-defined targets. Thus oculomotor adaptations that shift the location of a volume scotoma may assist fixation control, but are not associated with functional benefits in contrast sensitivity.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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