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P. E. Foeller, F. Ghasia, L. Tychsen; Upward Bias Manifested During Naso-Temporal Optokinetic Nystagmus (okn) in Macaque Monkeys With Infantile Strabismus. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2544.
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© ARVO (1962-2015); The Authors (2016-present)
Infantile (congenital) esotropia in humans and monkeys is accompanied by a constellation of horizontal and vertical cerebral gaze maldevelopments. The purpose of this study was to investigate the interaction between horizontal and vertical components of OKN.
Binocular image decorrelation (optical strabismus) was imposed on infant macaques by fitting them with prism goggles (n = 4 prism, 2 controls) for durations of 3 -12 weeks. Several months after the goggles were removed, horizontal and vertical OKN was recorded during monocular/binocular viewing, using binocular search coils and large-field stimuli.
In each strabismic monkey, strictly horizontal stimulus motion evoked diagonal slow-phase OKN, with the vertical vector directed upward. This OKN behavior was not present in control animals with normal binocular vision. . The relative magnitude (vertical / horizontal) of the upward component - measured as mean slow-phase velocity -- was 34% for nasalward stimulus motion compared to 19% for temporalward (upward vector = mean 13 deg for nasalward motion; 8 deg for temporalward). A diagonal OKN response was evident for horizontal, but not vertical, stimulus motion. Each of the strabismic animals also exhibited a naso-temporal asymmetry of horizontal OKN, with nasal stimulus motion evoking a more robust response.
The gaze pathways of primates with infantile strabismus are biased for nasalward and upward stimulus motion. The OKN behavior is consistent with findings of upward biases during latent nystagmus and smooth pursuit in infantile strabismus.
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