Intereye Comparison of Cirrus OCT in Early Glaucoma Diagnosis and Detecting Photographic Retinal Nerve Fiber Layer Abnormalities

PURPOSE: To compare the ability of various maps constructed using Cirrus optical coherence tomography (OCT), including the "intereye comparison" derived from the temporal superior inferior nasal temporal (TSNIT) map, in terms of glaucoma diagnosis and detection of RNFL defects identified in red-free fundus photographs. METHODS: This cross-sectional study was conducted on a total of 131 open-angle glaucoma patients with early-stage visual field defects (mean deviation ≤ -6.0 dB) and 56 healthy controls. Intereye differences were identified on TSNIT maps constructed by comparing the RNFL thickness curves of both eyes of individual patients and a separation of the RNFL thickness curves of either eye (by >50 μm) was defined as an abnormality. RESULTS: Among 131 red-free fundus photographic RNFL defects, 57 (44.0%) in the Clock-hour map, 51 (39.0%) in the Quadrant map, 37 (28%) in the Deviation map, 16 (12%) in the Thickness map, and 3 (2%) in the intereye difference obtained from the TSNIT map were misidentified. The intereye difference derived from the TSNIT map afforded a sensitivity superior to that of all other maps when used to evaluate eyes with glaucoma (98.0%, all P values < 0.05), and preperimetric eyes (97.7%, all P values < 0.001). CONCLUSIONS: Of the various maps constructed by the Cirrus OCT, comparison of the RNFL thickness curves of both eyes of an individual, which was possible using TSNIT map data, afforded the best diagnostic capability in terms of detecting photographic RNFL defects. Intereye comparisons of TSNIT thickness curves may be useful to detect early-stage glaucoma.