Optic nerve head stereoscopic digital imaging using bichromatic techniques.

The variability of optic nerve parameters obtained with versions 3.4 and 3.5 of the Topcon IMAGEnet computer stereo analysis system was studied. The consistency of horizontal cup-to-disc ratio, vertical cup-to-disc ratio, cup volume, neuroretinal rim area, neuroretinal rim-to-disc area, and the percentage of poorly correlated conjugate points (bad points) on the stereo pair was compared. The updated computer program for stereo analysis provides a significantly more accurate means to assess both the cup volume and the neuroretinal rim area as evidenced by the smaller number of bad points.