Interference fringe scale for absolute ocular fundus measurement.

Measurements of the human ocular fundus in the three spatial dimensions have not been absolute because measuring techniques have used the optical system of the eye as part of the total ophthalmoscopic system. The ophthalmoscopic magnification due to the total dioptric power of an individual eye can vary substantially from that of the average eye. A new method has been developed to form interference fringes on the fundus so that the fringe spacing can be calculated within a small error by using measured values. The photographed fringes then act as a scale at the fundus with the fringe spacings serving as the graduations, thus allowing accurate absolute measurements of the fundus through the interfering ocular media.