Comparison of optic disc topography measured by Retinal Thickness Analyzer with measurement by Heidelberg Retina Tomograph II.

PURPOSE To compare the optic disc topography measurements from a digitized laser slit-lamp and a confocal scanning laser ophthalmoscope (SLO). METHODS Ten normal subjects (10 eyes) were recruited. Topographic measurements of the optic disc were performed three times in all eyes using the Retinal Thickness Analyzer (RTA) and the Heidelberg Retina Tomograph II (HRT II), and the mean values determined. The mean values of 11 optic disc parameters were compared between the two instruments by the Wilcoxon signed rank test. To test the reproducibility of the topographic measurements, the coefficients of variation (CV) of the topographic parameters among the three measurements from each of the two instruments were compared using the Wilcoxon signed rank test. RESULTS The mean cup depth, mean retinal nerve fiber layer (RNFL) thickness, and RNFL cross-sectional area were significantly smaller when measured by RTA compared with HRT II (P =.0067, P =.0364, P =.0467, respectively). The mean CVs from the RTA were larger than those from the HRT II for all parameters; however, the differences in all parameters did not reach significance. CONCLUSION The RTA measured smaller z-axis values compared with the HRT II. The reproducibility of the topographic data was not significantly different between the instruments.