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D Troilo, DL Nickla; The Response to Form Deprivation by Occluder in the Marmoset Differs with Age of Onset . Invest. Ophthalmol. Vis. Sci. 2002;43(13):186.
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Purpose: Form deprivation by lid-suture in young adult primates has been shown to produce axial elongation and myopia that is reduced in magnitude compared to neonatal primates (Troilo et al., 2000; Smith et al., 2000). In this study we examine the effects of form deprivation by occlusion in marmoset monkeys across a range of ages that span the phase of rapid ocular growth, from young juvenile through prepubescent animals. Methods: 23 common marmosets were used in this study and were grouped by onset of deprivation (grp 1, 0-39 d, n=6; grp 2, 40-99d, n=9; grp 3, 100-200d, n=8). Monocular form deprivation was induced with a white translucent occluder worn for 28-88d (mean durations: grp 1, 32d; grp 2, 56d; grp 3, 51d). Refractive state, corneal curvature, and ocular axial dimensions were measured following cycloplegia. Both experimental and control eyes were measured multiple times before, during, and following the visual deprivation period. Results: Marmosets in all age groups are susceptible to visual form deprivation myopia, however the mean amount of axial elongation and myopia induced relative to the contralateral control eye was significantly greater (ANOVA, p<0.01) in grp 1 (0.33 mm, -8.25 D) compared to either grp 2 (0.18 mm, -3.46 D) or grp 3 (0.03 mm, -1.20 D). The response to form deprivation was variable in all groups and included some late- and non-responders. For all animals that responded (n=15), the age of deprivation onset was significantly correlated with the relative amount of vitreous chamber elongation (r=0.59) and myopia (r=0.58) induced. Following removal of the occluders, some animals in all groups (n=10) recovered by reducing their rate of axial growth. Conclusion: Marmosets are susceptible to form deprivation myopia produced by occlusion throughout the period of rapid eye growth during the first 200 days of life. The amount of axial elongation and myopia induced is inversely proportional to the age of onset of the deprivation, suggesting that the normal ocular growth potential may influence visually induced changes in eye growth and perhaps emmetropization. In addition, recovery from occluder-induced form deprivation was apparent in all groups, in contrast to what we find in visual deprivation by lid-suture (Troilo et al., 2000) and supports that visual regulation of eye growth occurs across a wide range of ages.
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