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R.S. Anderson, M.B. Vidinova–Zlatkova; Binocular Summation for Detection and Resolution of Blue–Yellow Gratings in Foveal and Peripheral Vision . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4566.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Previous studies of peripheral achromatic acuity found binocular improvements of 5–6% when the task was to detect the stimulus, but binocular improvements of 16% when the task was to resolve its orientation. This improvement implied some sort of higher level combination of the monocular retinal ganglion cell sampling arrays which limit peripheral grating resolution. We wished to determine if the same result obtained for blue–on–yellow gratings in either foveal or peripheral vision. Methods: Detection and resolution acuity were measured in the foveal and at 18 degrees in the superior retina of two experienced subjects using blue gratings superimposed on a bright yellow adapting background to selectively stimulate the short–wavelength sensitive (SWS) system. Thresholds were separately measured when viewing with the right eye (RE) left eye (LE) or both eyes (BE). Results: In the fovea, detection acuity was slightly but significantly higher than resolution acuity under all viewing conditions, with a narrow aliasing zone. Notably, detection and resolution performance both displayed an improvement of nearly 20% when viewing with BE. At 18 degrees, detection acuity displayed a greater superiority over resolution acuity than in the fovea for all viewing conditions. However, while resolution acuity again displayed a 16–20% improvement in performance for BE compared to RE or LE alone, detection performance displayed a 40% improvement when viewing binocularly, with a correspondingly larger aliasing zone. Conclusions: Unlike the achromatic system, which displays a binocular acuity improvement consistent with neural summation only in peripheral vision, the SWS system appears to display binocular neural summation in the fovea also, resulting in a significantly higher binocular resolution acuity. In addition, the level of summation for grating detection in the periphery is even higher again, perhaps as a result of more efficient contrast summation at a cortical level.
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