Macular Ganglion Cell Analysis for Early Detection of Glaucoma

Purpose To investigate the ability of Cirrus high-definition optical coherence tomography (Cirrus HD-OCT; Carl Zeiss Meditec, Dublin, CA) macular ganglion cell analysis (GCA) sector, deviation, and thickness maps to detect early glaucoma. Design Cross-sectional study. Participants We enrolled 131 eyes with early glaucoma (mean deviation >−6.0 dB) and 132 age- and refractive error–matched healthy eyes. Methods Macular GCA maps were obtained using Cirrus HD-OCT. The location, angular distance, and width of circumpapillary retinal nerve fiber layer (RNFL) defects were investigated by using red-free fundus photographs. The presence of a structural abnormality in the GCA map was defined as (1) yellow/red color codes in the sector map, (2) yellow/red pixels (>10) in the deviation map, and (3) blue areas in the thickness map. Main Outcome Measures The prevalence of and factors associated with the presence or absence of abnormal GCA findings were assessed. Results Among the 131 glaucomatous eyes, 105 (80.2%), 115 (87.8%), and 104 (79.4%) showed structural abnormalities in the GCA sector, deviation, and thickness maps, respectively. The absence of abnormal findings in the GCA maps of glaucomatous eyes was associated with the presence of RNFL defects in the superior hemisphere, a greater angular distance between the fovea and the RNFL defect, a narrower width of the RNFL defect, less severe visual field defects, or an isolated peripheral nasal step (outside 10 degrees of fixation) ( P< 0.05). A greater angular distance of the RNFL defect remained significant in multivariate analyses ( P< 0.05). Among the 132 healthy eyes, 28 (21.2%), 37 (28.0%), and 20 (15.2%) had abnormal findings in the GCA sector, deviation, and thickness maps, respectively. The presence of abnormal GCA findings in healthy eyes was associated with a higher degree of myopic refractive error ( P< 0.05). Conclusions Cirrus HD-OCT GCA maps showed a good ability to detect early glaucoma. However, GCA maps did not show abnormal findings in glaucomatous eyes when the angular distance between fovea and RNFL defect was great. These findings should be considered when diagnosing early glaucoma using GCA maps.