Reproducibility of optic disk evaluation in supine subjects with a Heidelberg Retina Tomograph II laser tomographic scanner

AIM The aim of this study was to determine the reproducibility and reliability of optic disk evaluation in supine subjects with a Heidelberg Retina Tomograph II (HRT II). METHODS One eye was randomly selected for evaluation by HRT II in each of eleven healthy subjects. Five images were obtained by each of two experienced operators at two separate visits with the subjects in both sitting and supine positions. A stand was constructed to allow stable, handheld operation of the HRT II head for imaging of the supine subjects. Measurements of optic disk parameters obtained in the supine position were compared with those obtained in the sitting position. The reliability of measurements in the supine position was evaluated by calculating both the coefficients of variation for measurements made by one observer on the first visit and the interobserver and intervisit intraclass correlation coefficients (ICCs); the values obtained were compared with those obtained for the sitting position. RESULTS Measurements of all parameters made in the supine position were highly similar to those made in the sitting position. The coefficients of variation obtained for each parameter in the sitting and supine positions ranged from 5.67% to 14.16% and from 2.18% to 16.08%, respectively. The interobserver ICC values in the sitting and supine positions were ≥0.978 and ≥0.989, respectively. The intervisit ICC values in the sitting and supine positions were ≥0.958 and ≥0.983, respectively. CONCLUSION Handheld operation of the HRT II in a custom-designed stand is feasible for optic disk evaluation in the supine subjects who were not able to maintain the sitting position.