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L. Sin, A.M. Wong, P. Foeller, D. Bradley, L. Tychsen; Duration of Binocular Decorrelation Predicts the Angle of Infantile Strabismus in Macaque Monkeys . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2451.
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Factors which perturb binocular correlation (and synchronous binocular signals from each eye) are known to promote strabismus in infant primates, with a strong bias in favor of convergent (esotropic) misalignment. The purpose of this study was to determine if the duration of image decorrelation was related systematically to the magnitude of the resultant strabismus.
Optical strabismus was created in 8 normal infant macaques (Macaca mulatta) by fitting them with prism goggles on day 1 of life. The goggles were removed after 3 wks (n=2), 3 mos (n=1) or 6 mos (n=3), emulating surgical repair of strabismus in humans at 3 mos, 12 mos, and 24 mos of age, respectively. Two monkeys wore plano lenses and served as controls. Several months after the goggles were removed, eye alignment was recorded using binocular search coils during automated single and alternate–cover testing. Alignment in each cardinal position was measured during steady fixation to assess concomitance.
The longer the duration of image decorrelation, the greater the magnitude of resultant concomitant esotropia. Only physiological (< 2 deg) heterophorias were detected in the control and 3–wk–duration groups. The 3–mos–duration monkey exhibited a 7.5 deg/13 PD esotropia. In the 6–mos group, one monkey exhibited a 15 PD and two others exhibited larger–angle esotropia (21–25 PD).
Longer durations of binocular decorrelation in infancy cause greater maldevelopment of the (tonic) vergence system manifested as larger–angle esotropia. These results reinforce the importance of restoring normal eye alignment in infancy within a short period of time.
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