Ocular rigidity in eyes with experimental myopia.

PURPOSE: To evaluate ocular rigidity in experimentally induced myopic eyes compared to contralateral control eyes in young rhesus monkeys.

METHODS

Eight rhesus monkeys (Macaca mulatta) were reared with monocular form-deprivation from 24 days to 150 days of age. Refraction, axial length, and intraocular pressure (IOP) were measured biweekly. After 150 days, ocular rigidity was assessed in both eyes via anterior chamber cannulation, in which controlled changes in anterior chamber volume were used to calculate the coefficient of ocular rigidity using Friedenwald's equation. Paired t-tests were used to compare form-deprived and control eyes, and Pearson's correlations were used to examine relationships between ocular rigidity, refraction, and axial length.

RESULTS

After 150 days, form-deprived eyes were significantly less hyperopic (+0.41 ± 3.89 D vs. +3.10 ± 3.01 D, P = 0.03) and had longer axial lengths (16.54 ± 0.81 mm vs. 15.90 ± 0.76 mm, P = 0.01) than control eyes. Mean ocular rigidity coefficients were not significantly different between form-deprived and control eyes (0.054 ± 0.008 vs. 0.050 ± 0.010 μL-1 P = 0.06).

DISCUSSION: Form-deprivation myopia in young rhesus monkeys produced significant axial elongation and myopic shifts but did not significantly alter the coefficient of ocular rigidity. Although ocular rigidity showed a decreasing trend with increasing eye size, the limited range of axial lengths may have constrained statistical power to detect a small-to-moderate difference in the ocular rigidity coefficients between treated and control eyes. This work establishes direct in vivo assessment of ocular rigidity in a primate model, laying the groundwork for future approaches to examine ocular biomechanics in myopia.