Abstract
Abstract: :
Purpose: Previously, we measured and compared monochromatic aberrations with growth in treated and untreated eyes during the experimental induction of myopia up to day 7. For a constant pupil size, higher–order monochromatic aberrations decreased in untreated eyes of goggled chicks during growth. Goggled eyes had significantly larger monochromatic aberrations than control eyes. Here we extend these experiments to day 14 and examine the possibility of a fellow eye effect in the untreated eye by measuring birds that grow without goggles. Methods: On the first day post–hatching, 16 chicks were unilaterally fitted with minus 15D goggles. The other eye acted as a control. On days 0, 2, 4, 7, 9, 10, and 14, goggles were removed for brief periods of time for Hartmann–Shack wavefront measurements (633nm light) and retinoscopy. Both eyes were measured in six additional birds allowed to develop without goggles. Hartmann–Shack images chosen for analysis corresponded to larger pupils and were presumed to be unaccommodated. Results: During growth in goggled birds, in the untreated fellow eyes, for a 1.6mm pupil, higher–order root mean square (rms) wavefront error showed a significant (p<0.0002) exponential decay and a reduction in second–order defocus terms. Higher–order monochromatic aberrations for treated eyes were significantly greater than untreated eyes beyond day 2 (p<0.05). The overall trend with age in treated eyes followed a third–degree polynomial (rms = 0.0476 + 0.0102age – 0.0016age2 + 0.0001age3, rms in microns and age in days). Initially, goggles interfered with the normal reduction of aberrations with age. Beyond day 7, higher–order rms wavefront error decreased as the eye completed emmetropization to the goggle. There were no significant differences in overall higher–order aberrations or mean ocular refraction between untreated fellow eyes and eyes in chicks developing without goggles. Hence, there appears to be no fellow eye effect on rms aberrations in the goggled birds. Conclusions: Lens induction of myopia causes changes in the optical components of the treated eye relative to the control eye and the eyes of untreated birds. The subsequent decrease in aberrations as refractive error emmetropizes to the goggle power, further suggests that aberrations also actively emmetropize. Refractive error and aberrations emmetropize at different rates. These temporal relationships require further investigation.
Keywords: emmetropization • optical properties • myopia