Segmental analysis of computerized optic nerve head imaging

We evaluated a new method of segmental analysis of the array of numbers representing the depths at points on the optic nerve as generated by a computerized retinal topographic imaging system (the Humphrey Retinal Analyzer). We divided the observed optic nerve head into five rectangular areas, determined the mean depth of each of these areas, and compared them statistically. Intraobserver, interimage, and interobserver variability were calculated. The range of intraobserver variability (+/-SEM) was +/-1.2 to +/-12.0 mum, median 4.6 mum. Interimage variability ranged from +/-3.0 to +/-30.8 mum, median 14.7 mum. Interobserver variability, assessed by intraclass correlation coefficient and two-way analysis of variance, showed observer-to-observer variability was not significant as compared to subject variance and subject-observer interaction variance. Clinical studies further evaluating this segmental analysis of computerized data from the Heidelberg Retinal Tomograph are in progress.