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Lisa A. Ostrin, Janine Mok-Yee, Christine F. Wildsoet; Behavioral Measures of Spatial Vision during Early Development in Pigmented and Albino Guinea Pigs. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6296.
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© ARVO (1962-2015); The Authors (2016-present)
While emmetropization is known to be vision dependent, knowledge about the early visual development of guinea pigs, an increasingly popular model for studies of myopia, is sparse. Here, we report on behavioral measures of spatial vision in pigmented and albino guinea pigs made during the first post-natal month when most experimental studies of emmetropization and myopia are undertaken.
Optokinetic motor responses were recorded from pigmented (n=13) and albino (n=5) guinea pigs, aged 1 day to 1 month. Sine wave grating stimuli were presented in a computerized virtual cylinder (OptoMotry, Cerebral Mechanics) at a drift speed of 12 d/sec. Binocular spatial frequency sensitivity was determined with 100% contrast gratings, for clockwise and counterclockwise motion. Contrast sensitivity was determined at spatial frequencies of 0.15, 0.3, 0.5, and 0.7 c/d. Monocular testing was also undertaken to evaluate the preferred direction for each eye.
Visual spatial resolution was similar for 1-day old pigmented and albino guinea pigs, with thresholds of 0.87±0.05 and 0.86±0.06 c/d, respectively (p=0.69), and slightly but significantly improved over the first month, by about 0.1 c/d (0.97±0.07 and 0.98±0.04 c/d, respectively, p<0.005 for both). Contrast sensitivity peaked at 0.3 c/d, with a contrast threshold of 4.3±1.3%. Monocular testing revealed each eye to be more sensitive to gratings drifting in the temporal to nasal direction; thresholds for the non-preferred direction were 0.5±0.1 c/d.
Compared to mice and rats, guinea pigs have high spatial resolution at birth, consistent with their precocial nature, with further improvement during the first month of life. Thus the visual effects of optical defocus manipulations used in myopia studies, should be relatively invariant over this age period. Although the increased intraocular light scatter in albino eyes may be expected to lead to optical degradation of the retinal image, the visual spatial resolution thresholds of pigmented and albino animals were similar. On-going studies of the optical aberrations may provide insight into this unexpected result. These types of behavioral tests should be incorporated into studies that assess the effects of defocus-induced eye growth.
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