Influence of Age on the Rate of Estimated Retinal Ganglion Cell Counts in Healthy Eyes

Abstract

To evaluate aging effects on estimated retinal ganglion cell (RGC) counts in healthy eyes. This was a longitudinal observational cohort study involving 100 eyes of 50 healthy patients recruited from Diagnostic Innovations in Glaucoma Study (DIGS) and African Descent and Glaucoma Evaluation Study (ADAGES). Subjects were followed for an average of 4.9 ± 2.6 years. All patients underwent standard automated perimetry (SAP) visual field testing and optical coherence tomography (OCT) on follow‐up visits. Estimated RGC counts were obtained by a previously described method using SAP sensitivity thresholds and OCT retinal nerve fiber layer measurements. Linear mixed effects models were used to investigate the relationship between age and rates of change in estimated RGC counts over time. The mean age at baseline was 49.4 ± 16.2 years, ranging from 22.9 to 90.0 years. At baseline, average estimated RGC count was 1,144,010 ± 222,084 cells. In univariable model, the rate of change in estimated RGC count was ‐6,880 ± 2,398 cells/year (P = 0.004). Analyses were also performed adjusting for baseline age, gender, race, OCT signal strength and axial length. After adjusting for confounding factors, the rate of estimated RGC loss was ‐6,276 ± 2,441 cells/year (P = 0.010) in healthy eyes. There was a significant age‐related decline in estimated RGC counts obtained from combining information from structural and functional tests. After accounting for confounding factors, the age‐related decline found was similar to those obtained in previous histologic studies reported on the literature.