Digital Photogrammetry Of The Optic Nerve Head

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Abstract
A digital photogrammetric method capable of providing quantitative measurements from stereophotographs of the optic nerve head has been utilized in our laboratory to study the optic cup in patients with ocular hypertension and chronic glaucoma. Studies on the reproducibi-lity of the digital photogrammetric technique of optic nerve head photographs taken with various cameras has revealed that (1) reproducibility was significantly better when simultaneous stereo-photographs were analyzed and (2) the Donaldson stereofundus camera provided the best reproducibility of the majority of geometric measurements in optic cups of various sizes. In addition, it has been determined that the shallower cups encountered larger percentage errors. Improvements in parameter reproducibility have been obtained when finer sampling intervals have been used during film digitization. An additional study comparing reproducibility of cup parameters as determined by the digital photogrammetric procedure with those values obtained from analog photogrammetry and manual analysis revealed generally superior reproducibility of the digital photogrammetric analyses in the eyes studies. Preliminary observations utilizing the digital photogrammetric procedure in a modified Zeiss model eye indicated that minor shifts in camera posi-tion did not alter the reproducibility of the technique.

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