Minimal spot size on the retina formed by the optical system of the eye.

A knowledge of the quality of the ocular optical system is of primary importance in light- and laser-photocoagulation of the fundus. A study was therefore undertaken to determine the minimal spot size of a Helium-Neon laser focused on the retina of rabbits: freshly enucleated eyes were carefully mounted in a specially designed eye holder. A small hole was then trepanized through the sclera and neural retina in the macular region. A minimal spot was produced on the retina and the spot size was measured by scanning the intensity distribution of an enlarged image. It was shown that a diffraction limited spot size can be obtained under certain circumstances. The light scattering out of the focus, however, is about fify percent.