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Gad Serero, Maria Lev, Uri Polat; Unconscious meridional rivalry in oblique astigmatism. Journal of Vision 2019;19(10):63b. doi: https://doi.org/10.1167/19.10.63b.
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Introduction: Binocular vision is not a simple summation of the monocular inputs. Binocular summation (BS) is sub-linear, where stimulating both eyes only improves sensitivity by a factor of ~1.4 compared to the linear sum (factor ~2), effect that is usually attributed to interocular suppression. Binocular rivalry (BR) occurs when conflicting images are presented to the eyes, producing alternating periods of monocular dominance. In astigmatism, the image falling on the retina is blurred in one meridian. In oblique astigmatism (OA), the blur meridian is opposite, 45° in one eye and 135° in the other, resulting in two conflicting images. Here we explored the influence of astigmatism on BS and BR. Methods: Fully corrected subjects (n=21) divided to OA (n=8) and normal controls (n=13) were tested on contrast detection and collinear facilitation (CF) in different orientations and eyes (monocular, binocular), as well as on subjective report of the sharpness of oriented lines. BS was measured using contrast detection of Gabor patches. In BR, the 2 monocular images available for processing by the visual system were identical due to the optical correction. Results: BS of single target was better by 1.4 than the monocular thresholds. The difference in BS between meridians and groups was not significant. However, the monocular CF was significantly better in the clear than the blurred meridian in the oblique astigmatic group, reminiscent of the lateral facilitation of meridional amblyopia. Monitoring binocularly static oriented lines, OA subjects reported alternating sharpness, similar to the classical BR. Conclusions: Our results show that subjects with normal vision may have abnormal lateral interactions similar to meridional amblyopic subjects. This effect may lead to competition for dominance between the eyes for the strongest visual input, leading to bi-stable natural perception, and to a binocular unconscious meridional rivalry affecting BS in OA people.
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