A comparison of stereoscopic and monoscopic evaluation of optic disc topography using a digital optic disc stereo camera

Aims-To compare stereophotographic and monophotographic optic disc assessme nts made using a digital optic disc stereo camera. Methods-Stereo digital optic disc photographs of 150 selected patients who had presented to a glaucoma clinic were assessed by two masked observers on separate occasions using (1) the stereophotographs and a stereoviewer, (2) a single image from the same stereopair. Results were analysed for both ri ght and left eyes separately. 95% tolerance limits for change (TC) and intr aclass correlation coefficients (ICC) were calculated and a multivariate an alysis using a general linear model for repeated measures was performed. Results-A total of 201 optic disc images of 150 patients (84 females, 108 l eft eyes) were analysed. Mean age of patients was 64 years. The results for right eyes are as follows (similar results were obtained for left eyes). I ntraobserver (stereoscopic compared to monoscopic) measurements of. horizon tal cup:disc ratios (CDR), ICC = 0.5995 and 0.7269, TC = 34% and 27%; verti cal CDR, ICC = 0.8298 and 0.817, TC = 25% and 27%; area CDR, ICC = 0.7757 a nd 0.8259, TC = 28% and 25%; circumference CDR, ICC = 0.7618 and 0.8103, TC = 28% and 25%. Interobserver measurements of. horizontal CDR, ICC stereosc opic (SS) = 0.7287; monoscopic (MS) = 0.5030; TC SS = 30%; MS = 32%; vertic al CDR, ICC SS = 0.8439; MS = 0.7106; TC SS = 25%; MS = 31%; area CDR, ICC SS = 0.8392; MS = 0.6276; TC SS = 26%; MS = 32%; circumference CDR, ICC SS = 0.8433; MS = 0.6438, TC SS = 26%; MS = 31%. Systematic bias between obser vers and between methods was within acceptable limits. Conclusions-This study using a digital stereo camera indicates that there m ay be little benefit of stereoscopic imaging over monoscopic imaging despit e demonstrating small but inconsistent differences between both observers a nd methods.