Spherical aberration of the crystalline lens.

Split beams of varying separations from a helium-neon laser were directed through the crystalline lenses of a number of vertebrates. Photographs of the focal effects indicate the extent to which the refractive index variation of the lens and lens shape control spherical aberration. Of the fish studied, only rock bass lenses are relatively free of spherical aberration. Both goldfish and yellow perch exhibit substantial amounts of positive spherical aberration. Varying amounts of negative spherical aberration are present in frog, juvenile duck, dog and rat lenses. Positive and negative spherical aberration is found in human and cat lenses while cow, pig, lamb and rabbit lenses are almost free of aberration.