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Lawrence Tychsen, Paul E. Foeller, Dolores Bradley; Birth-onset Vs Later-onset Infantile Strabismus In Macaque Monkeys: 1. Effects On Short-latency Vergence And Stereopsis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6347. doi: https://doi.org/.
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In previous work we have shown how the duration of birth-onset strabismus predicts the severity of visuomotor deficits. The purpose of this study was to determine how the duration of strabismus effects the development of stereopsis and fusional (disparity) vergence pathways in esotropic macaques when strabismus onset is delayed until age 3 weeks.
Eight infant macaques were fitted with prism goggles at three weeks of age to induce large magnitude optical strabismus. The goggles were removed, emulating surgical repair of strabismus in humans, after 3 wks (n=2), 6 wks (n=2), 9 wks (n=2) or 12 wks (n=2). At age 1 year, disparity-vergence eye movements were recorded using scleral coils. Forced-choice preferential looking technique was used to measure stereopsis.
Each animal developed a constant, alternating esotropia. The reversibility of the esotropia and robustness of restored vergence and stereopsis were related systematically to the timeliness of goggle removal (strabismus duration). The deficits were equal to or more severe than those of birth-onset monkeys.
Longer durations of binocular decorrelation in infancy cause greater maldevelopment of the vergence system and stereopsis, whether onset occurs at birth or after weeks of normal binocular experience. These results reinforce the importance of restoring normal eye alignment in infancy within a short period of time.
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