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L. Tychsen, C. Scott, P. Foeller, D. Bradley; Early versus Delayed Repair of Infantile Strabismus in Macaque Monkeys. III. Effects on Short–Latency Fusional Vergence . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2543.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Infantile esotropia is a maldevelopment of fusional vergence. Several reports in humans have suggested that normal fusional vergence can be restored by early surgery. The purpose of this study was to determine how repair timeliness affects development of fusional (disparity) vergence pathways in esotropic macaques. Methods: Normal infant monkeys (9 animals) had esotropia induced by prism rearing, which varied in duration from 3–24 wk (the equivalent of 3–24 mos of strabismus in humans). At age 1–2 years, a battery of ocular motor and perceptual tests were performed using eye movement and electrophysiologic recordings. Results: Each animal developed a constant, alternating esotropia. The reversibility of the esotropia and robustness of restored vergence were related systematically to the timeliness of goggle removal (the equivalent of delivering a fixed "dosage" of surgery after short versus longer durations of strabismus). Vergence responses in the early treatment group approached those of control monkeys (peak velocities for 1–2 degrees of disparity at latencies 60–80 msec). Delayed repair animals had negligible or weak vergence responses, even for large (5–10 degree) disparities, accompanied by latent nystagmus, pursuit/OKN asymmetry, and DVD. Conclusions: The CNS fusional vergence pathways of infant primates can recover from constant esotropia so long as the duration of the deviation does not exceed the equivalent of 3 mos in human. The present findings and those of our earlier reports provided evidence that correction of infantile esotropia is beneficial for brain repair.
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