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P.E. Foeller, A.M. Wong, D.V. Bradley, L. Tychsen; Early versus Delayed Repair of Infantile Strabismus in Macaque Monkeys: Effects on Motion VEP . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4829.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Infantile esotropia is typically associated with nasotemporal asymmetry of motion VEP (mVEP) responses. The purpose of this study was to determine how early versus late repair of strabismus influences the development of mVEP in primates. Methods: Infant macaques were fitted with goggles on day 1 of life. The Early Repair group (2 experimental and 1 control) wore the goggles for a period of 3 wks (the equivalent of 3 months in humans). The Delayed Repair group (3 experimental and 1 control) wore the goggles for a period of 3 or 6 months (the equivalent of 12-24 mos in humans). The experimental animals wore prism goggles to induce optical strabismus of 11.4 - 22.8 deg while the control animals wore goggles with plano lenses. At age 1 year, mVEPs were recorded during monocular viewing of vertically oriented gratings that oscillated horizontally at temporal frequencies of 6 to 11 Hz and at spatial frequencies of 1 to 3 cycle/deg. Nasotemporal mVEP asymmetry was defined by "asymmetry index" > 0.4 at 11 Hz and > 0.25 at 6 Hz, and interocular phase difference of 180 ± 40 deg. Results: When tested at higher spatiotemporal frequencies, normal control and Early Repair monkeys had a mean asymmetric index of 0.34 and 0.28, respectively, with interocular phase difference < 80 deg in both groups. In contrast, Delayed Repair and unrepaired naturally strabismic monkeys had a mean asymmetric index of 0.49 and 0.84, respectively, with interocular phase difference > 140 deg in both groups. Delayed Repair and unrepaired naturally strabismic monkeys also had persistent mVEP asymmetry when tested using lower spatiotemporal frequencies. Conclusions: Early repair of strabismus in primates prevents the development of nasotemporal mVEP asymmetry that typifies infantile esotropia in humans.
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