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Patrick J Lee, Federico G Velez, Joseph L Demer, Stacy Pineles; Effects of visual noise on binocular summation in strabismic patients without amblyopia. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4087. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Patients with strabismus often complain of difficulty navigating through visually stimulating environments without clear explanation for this symptom. Binocular summation (BiS), defined as the superiority of binocular over monocular viewing on visual threshold tasks, is decreased in conditions that cause large interocular differences in visual acuity, but is not well studied in strabismic populations without amblyopia. We hypothesized that strabismus may lead to decreased BiS for tasks related to discrimination within increased background complexity. The goal of this study was to test the extent of BiS in strabismic patients during discrimination of a luminance target disk embedded in visual noise.
Ten exotropic, ten esotropic, and thirteen age-matched control subjects participated. Performance of a task detecting a luminance-target was measured 0, 10 and 20 μdeg2 of visual noise for binocular and monocular conditions. BiS was calculated as the ratio of binocular contrast sensitivity to monocular contrast sensitivity for the target embedded in noise.
Strabismic patients had lower BiS values than controls, with a significant decrease on linear regression in strabismic patients at 20 μdeg2 of noise (p=0.05), with a trend towards significance at 10 μdeg2 of noise (p=0.07). Strabismic patients showed a mean binocular inhibition (summation ratio<1) at both noise levels.
Our findings support our hypothesis that strabismus can lead to decreased BiS and even binocular inhibition. Despite literature showing enhanced BiS in visually demanding situations such as high levels of visual noise or low contrast, BiS was not significantly affected by visual noise in either group.
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