The refractive error of the fish eye

Abstract

Goldfish eyes were rapidly frozen and sectioned and the lens radii and distances between the lens and the two retinal surfaces were measured. These measurements were used to calculate the refractive error at each of the two retinal surfaces. A comparison with refractive errors determined with a retinoscope just prior to freezing indicates that, in fish, the retinoscopic finding is based upon reflection from the retina-choroid border and not from the retina-vitreous surface. A subsequent examination of longitudinal chromatic aberration of fish lenses indicates that a substantial amount of chromatic aberration exists. The consideration of this finding in association with the restricted spectral range ol aquatic habitats suggests that the fish eye is less hyperopic in its natural environment than that found using conventional non-monochromatic measurements of refractive error.