Measurement variability in digital analysis of optic discs.

The optic disc of nine patients with typical glaucomatous disc damage and ten normal controls has been studied by means of the Optic Disc Analysis program of the Topcon Image-net System. Vertical, horizontal and average cup/disc ratio (VC/D, HC/D, AC/D), disc, cup, rim area (DA, CA, RA), cup volume (CV) have been evaluated and the coefficient of variation (COV) of multiple measurements was calculated. For intra-observer intra-image variability assessment, sterovideographs of each disc were taken once and analyzed 10 times (COV range: 1.39-12.08%). Intra-observer interimage variability was evaluated on eight stereovideographs of each disc taken at one minute intervals (COV range: 1.63-96%). Inter-observer intra-image measurements were taken on each disc by 5 different observer (COV range: 1.28-27.08%).