Spherical aberration of the lens of the ground squirrel (Spermophilis tridecemlineatus).

Spherical aberration of the excised ground squirrel lens was measured by photographing the variation in back vertex distance for parallel helium - neon laser beams of various separations. The results indicate high levels of negative spherical aberration in amounts similar to that measured earlier for the rat lens. The effect of the aberration on resolution ability is likely minimized by the small size of the ground squirrel pupil in diurnal conditions and possibly by the existence of positive corneal aberration.