Rates of Ganglion Cell-Inner Plexiform Layer Thinning in Normal, Open-Angle Glaucoma and Pseudoexfoliation Glaucoma Eyes: A Trend-Based Analysis

Abstract

The purpose of this study was to determine the rate of ganglion cell-inner plexiform layer (GCIPL) thinning by Cirrus high-definition optical coherence tomography (HD-OCT) in normal eyes and open-angle glaucoma (OAG) and pseudoexfoliation glaucoma (PXG) eyes. This was a longitudinal observational study. We evaluated 282 subjects who visited a glaucoma clinic of a tertiary hospital in Korea: 60 healthy eyes, 193 medically treated OAG eyes, and 29 medically treated PXG eyes with a minimum 3-year follow-up involving serial spectral-domain OCT measurement of GCIPL thickness. The rates of thinning in the GCIPL thickness of the global region, six macular sectors, and minimum thickness were determined by linear mixed model and compared among the normal, OAG, and PXG groups. Additionally, the GCIPL thinning rates were compared between normal-baseline-IOP OAG (normal-tension glaucoma [NTG]) and high-baseline-IOP OAG (high-tension glaucoma [HTG]) eyes. The mean rates of GCIPL thinning were -0.31 μm/y in the normal eyes, -0.49 μm/y in OAG, and -1.46 μm/y in PXG. The differences in the mean GCIPL thinning rates were statistically significant between OAG and PXG (normal versus OAG, P = 0.231; OAG versus PXG, P < 0.001; normal versus PXG, P < 0.001). Among the eyes with OAG, the treated NTG and HTG eyes showed no significant difference in GCIPL thinning rate (NTG versus HTG = -0.41 μm/y versus -0.66 μm/y, P = 0.123). We determined the GCIPL thinning rates for normal and undertreated OAG and PXG eyes. Differences existed among the normal eyes and glaucoma types, with PXG progressing significantly faster than OAG.