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Apoorva Karsolia, Scott Stevenson, Vallabh E Das; Spatial localization during monocular and dichoptic viewing. Invest. Ophthalmol. Vis. Sci. 2020;61(7):5094.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the accuracy and precision of localization under monocular and dichoptic viewing conditions in individuals with normal ocular alignment, to ultimately evaluate the role of eye position signals in spatial localization in individuals with strabismus.
Stimuli were rear projected onto a curved screen (field of view 180° x 90°), with a dynamic noise background. A target disc (1.5°) was flashed for 1 sec, followed after a delay (0.25, 0.5, 1, 1.5, 2, 5, or 7 secs) by a response disc. Subjects fixated on the response disc, and used a mouse to move it to the remembered location of the target. The experiments were performed under monocular viewing and dichoptic viewing with red-green glasses. Under dichoptic viewing, four conditions [green target – green response cue (GG), green-red (GR), red-green (RG), and red-red (RR)] were tested. Errors in localization were calculated as the difference between the estimated and real positions of the target cue. For each subject, ~30 trials with same time intervals were pooled, and localization error was quantified as the area of the 68th percentile bivariate contour ellipse (BCEA).
Under monocular viewing (n=8), the mean monocular horizontal localization error was close to 0° and was not different between 0.5 and 7 seconds (p>0.05, ANOVA) in all subjects. BCEA increased linearly with time under monocular viewing in all subjects. During dichoptic testing (n=3), mean horizontal error from same eye trials was close to 0° (mean GG: 0.30°, mean RR: 0.46°). For alternate eye trials, there was a shift in horizontal localization error (mean GR: -3.68°, mean RG: -5.27°) that corresponded to the mean phoria (mean GR: -2.78°, mean: RG -2.68°) recorded during the testing procedure; however trial-by-trial correlation between phoria and localization error was weak. For same eye trials, the BCEA increased linearly with time, but for alternate eye trials, the BCEA reached saturation for larger time intervals in 2/3 subjects.
Spatial localization becomes progressively worse with time. Under dichoptic viewing, subjects are unable to compensate for their phoria during spatial localization. An interpretation is that oculomotor proprioception may not provide the required feedback of eye position. Testing strabismus subjects could add insight into the relationship between eye position feedback and spatial localization.
This is a 2020 ARVO Annual Meeting abstract.
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