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Janice Marie Wensveen, Earl L Smith, Li-Fang Hung, Baskar Arumugam, Ronald Harwerth; Multiple Short Daily Periods of Normal Visual Experience Can Preserve Stereopsis in Optical Strabismus. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3442. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Stereopsis is preserved during optical strabismus in young monkeys by 2 continuous hours of binocular vision per day. We investigated the effect on stereopsis of multiple short periods of binocular vision (totaling 1 hour/day) to determine whether normal visual experience must total 2 hours, and whether that interval needed to be continuous.
Methods: Starting at 4 weeks of age and continuing for 6 weeks, four infant monkeys were reared with 30 prism diopters base-in. Monkeys were provided four 15-minute periods of binocular vision each day by replacing the prisms with plano lenses. Results were compared to monkeys that were similarly prism-reared either continuously, or allowed 2 hours of binocular vision per day for 4 weeks, 6 weeks, or 16 weeks. Six normally reared monkeys provided control data. Behavioral methods were employed to measure spatial contrast sensitivity, eye alignment, and stereopsis with Gabor and random dot targets.
Results: All four monkeys maintained normal binocular eye alignment. Three of the monkeys reared with four 15-minute periods of binocular vision each day demonstrated stereopsis ranging from near-normal (50 arcsec) to within a factor of 10 (150 arcsec) of normal (20 arcsec). One monkey developed a myopic anisometropia and despite having relatively equal contrast sensitivity with optical correction, could not discriminate stereoscopic depth despite extensive training.
Conclusions: During early development, the effects of normal visual experience are weighed more heavily than those of abnormal vision. Multiple short periods of binocular vision were effective in preserving near-normal stereopsis in monkeys that were without other impediments to normal disparity processing. These results are encouraging for parents of strabismic children, in that substantial beneficial effects could result from relatively short multiple daily intervention periods.
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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