Circle- and Grid-Wise Analyses of Peripapillary Nerve Fiber Layers by Spectral Domain Optical Coherence Tomography in Early-Stage Glaucoma

PURPOSE. To study diagnostic performances of circle-and grid-wise analyses of peripapillary retinal nerve fiber layer thickness (RNFLT) using spectral domain optical coherence tomography (SD-OCT) in early-stage glaucoma. METHODS. Eighty-nine open-angle glaucoma (OAG) eyes (mean deviation: 2.5 +/- 1.8 dB) and 89 age-matched normal eyes were studied. Peripapillary RNFLT was analyzed using an SD-OCT raster scan in a 6.0 x 6.0-mm area. Averaged RNFLT was calculated over 0.1 x 0.1-, 0.21 x 0.21-, or 0.42 x 0.42-mm grids in the peripapillary area (grid method), or arcuate sector areas between 2.8- and 4.0-mm diameter circles (annulus method), or along a 3.4-mm diameter circle (circle method). Normative data-based cutoff values for averaged RNFLT and number of abnormal grid locations (grid method) or sectors (annulus or circle method) were varied. RESULTS. The grid method showed the best power of sensitivity/specificity of 0.94/0.96 with any five contiguous 0.21 x 0.21-mm grid locations with a 2.5 percentile cutoff, followed by the annulus method of 0.81/0.98, and the circle method of 0.76/0.97, with 308 sectors. The sensitivity of the grid method was significantly higher than that of the other methods (P < 0.001), whereas the specificity was not. Coefficients of variation and interclass correlation coefficients of intervisit measurements of averaged RNFLT over each 0.21 x 0.21-mm grid were 3.1% to 11.3% and 0.937 to 0.760, respectively, in a separate OAG patient group. CONCLUSIONS. Grid-wise analyses of peripapillary RNFLT for differentiating early-stage glaucoma showed >0.90 sensitivity and >= 0.95 specificity.