Comparison of Optic Nerve Head Parameter Measurements Obtained by Time-domain and Spectral-domain Optical Coherence Tomography

PURPOSE:: To compare the measurements of the optic nerve head (ONH) parameters provided by time-domain (TD) and spectral-domain (SD) optical coherence tomography (OCT). METHODS:: Four ONH parameters were analyzed: optic disc area, rim area, cup-to-disc area ratio (CDR), and vertical cup-to-disc ratio (VCDR). Stratus OCT and Cirrus HD-OCT were used to obtain measurements by TD-OCT and SD-OCT, respectively. Stratus OCT measurements were collected before and after manual correction of the ONH edges. RESULTS:: Twenty healthy participants and 20 patients with glaucomatous eyes were enrolled. Although manual correction of Stratus OCT measurements reduced the differences compared with Cirrus HD-OCT, the latter measured a smaller mean disc area than Stratus OCT in healthy (2.02±0.31 vs. 2.18±0.29 mm, P=0.0003) and glaucomatous eyes (1.92±0.35 vs. 2.19±0.38 mm, P<0.0001). Cirrus HD-OCT measured a smaller rim area than Stratus OCT in healthy (1.31±0.30 vs. 1.56±0.32 mm, P<0.0001) and glaucomatous eyes (0.80±0.25 vs. 0.97±0.36 mm, P=0.0052), a higher CDR (0.55±0.11 vs. 0.49±0.11, P<0.0001) and VCDR in healthy eyes (0.55±0.11 vs. 0.49±0.11, P<0.0001), and a higher CDR in glaucomatous eyes (0.74±0.10 vs. 0.58±0.18, P<0.0001). No statistically significant differences were detected for VCDR in glaucomatous eyes. All measured values showed good correlation (r≥0.70). Large 95% limits of agreement between the 2 devices were found for most parameters. CONCLUSIONS:: ONH parameter measurements provided by TD-OCT and SD-OCT show significant differences and cannot be considered interchangeable.