Absolute ocular fundus dimensions measured by multiple-beam interference fringes.

Multiple-beam interference fringes have been projected onto the retina to serve as a size reference for fundus photography. The absolute fringe spacing is determined by measurable parameters. The interference fringes are extremely narrow so that fringe maxima and fundus structures can be perceived equally well, and a high precision of measurement is achieved. The method has been applied to a model eye of varying ametropia (within +/- 7 diopters). The reproducibility of measurement is within 0.5%. In vivo measurements on human eyes demonstrate the clinical applicability.