Number of ganglion cells in glaucoma eyes compared with threshold visual field tests in the same persons

PURPOSE. To compare the number of retinal ganglion cells (RGCs) topographic ally mapped with specific visual field threshold test data in the same eyes among glaucoma patients. METHODS. Seventeen eyes of 13 persons with well-documented glaucoma histori es and Humphrey threshold visual field tests (San Leandro, CA) were obtaine d from eye banks. RGC number was estimated by histologic counts of retinal sections and by counts of remaining axons in the optic nerves. The location s of the retinal samples corresponded to specific test points in the visual field. The data for glaucoma patients were compared with 17 eyes of 17 per sons who were group matched for age, had no ocular history, and had normal eyes by histologic examination. RESULTS. The mean RGC loss for the entire retina averaged 10.2%, indicating that many eyes had early glaucoma damage. RGC body loss averaged 35.7% in eyes with corrected pattern SD probability less than 0.5%. When upper to lo wer retina RGC counts were compared with their corresponding visual field d ata within each eye, a 5-dB loss in sensitivity was associated with 25% RGC loss. For individual points that were abnormal at a probability less than 0.5%, the mean RGC loss was 29%. In control eyes, the loss of RGCs with age was estimated as 7205 cells per year in persons between 55 and 95 years of age. In optic nerves from glaucoma subjects, smaller axons were significan tly more likely to be present than larger axons (R-2 = 0.78, P < 0.001). CONCLUSIONS. At least 25% to 35% RGC loss is associated with statistical ab normalities in automated visual field testing. In addition, these data corr oborate previous findings that RGCs with larger diameter axons preferential ly die in glaucoma.