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M.D. Richards, A.M. Wong, P. Foeller, D. Bradley, L. Tychsen; Duration of Binocular Decorrelation Predicts the Intensity of Fusion Maldevelopment (Latent) Nystagmus in Strabismic Macaque Monkeys . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2514.
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© ARVO (1962-2015); The Authors (2016-present)
Infantile esotropia is linked strongly to latent fixation nystagmus (LN) in human infants, but many features of this co–morbidity are unknown. The purpose of this study was to determine how the duration of early–onset strabismus affects the prevalence and magnitude of LN.
Optical strabismus was created in 9 infant macaques by fitting them with prism goggles on day 1 of life. The goggles were removed after 3 wks (n=2), 3 mos (n=2) or 6 mos (n=3), emulating surgical repair of strabismus in humans at 3, 12, and 24 mos of age, respectively. Two control monkeys wore plano lenses. Several months after the goggles were removed, eye movements during fixation tasks were recorded using search coils.
Each animal in the 3–mos– and 6–mos–duration groups showed LN of ∼2–6 deg/sec during monocular fixation. In the 3–wk–duration group, one monkey exhibited subtle LN (∼0.5 deg/sec) in only one eye, while the other monkey exhibited no LN (indistinguishable from control animals). The longer the duration of binocular decorrelation, the greater the LN: mean slow–phase eye velocity (SPEV) in the 6–mos–duration group was 3 times greater than that in the 3–mos group, and 20 times greater than in the 3–wk group (ANOVA, p = 0.006). Mean LN intensity (LN amplitude x frequency) followed the same pattern: the intensity in the 6–mos group was 3 times greater than that in the 3–mos group, and 20 times greater than that in the 3–wk group (ANOVA, p = 0.01).
Early correction of strabismus (i.e. reduction of binocular decorrelation) reduces fusion maldevelopment/latent fixation nystagmus in primates. These findings indicate that early correction of infantile strabismus is beneficial for brain development.
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