Reproducibility of the measurements of the optic nerve head topographic variables with a confocal scanning laser ophthalmoscope.

PURPOSE To determine the optic nerve head topographic parameters with the least variability in repeat measurements. METHODS We randomly selected and evaluated 1 eye each of 20 healthy subjects, a total of 20 eyes. We used the confocal scanning laser ophthalmoscope (CSLO) for optic nerve head analysis. The disc area and a total of 13 parameters were determined by Top SS. Each subject was examined five times, each time on a different day, during a 2-month period. We obtained a series of five 10 x 10 degrees images for each eye per visit. Three of the five images were randomly selected to create a mean image. Coefficients of variation of each of the 13 variables studied were calculated separately by using those five different optic nerve head topographic measurements. RESULTS The subjects were 11 women and 9 men. The mean age of the subjects was 30.5 +/- 6.9. The mean optic disc areas were 2.26 +/- 0.39 mm(2) and 1.96 +/- 0.37 mm(2) for the men and the women, respectively (P >.05). The mean coefficient of variation for measurement of the variables was found to range between 1.2% and 9.8%. The variables, cup shape, volume above, average depth, and volume below, were found to yield the best reproducible measurements. CONCLUSION The CSLO with its highly reproducible measurements (<10% error) offers a highly objective, safe, and effective method for clinical use in measurements of the topography of the optic nerve head. The subtle differences in the variables, cup shape, volume above, average depth, and volume below, may be of vital importance in the follow-up of those diseases requiring longitudinal monitoring of the optic nerve head, namely ocular hypertension and glaucoma.