Temporal macular ganglion‐cell inner plexiform layer thinning is a hallmark of early glaucomatous damage

Purpose To investigate the pattern of damage affecting the GCIPL and to compare it to the topographical RNFL thinning in early glaucoma (EG). Methods Total Average (Tot Avg) and quadrant (S, I, N, T) RNFL, Tot Avg and sector (ST, S, SN, IN, I, IT) GCIPL thicknesses were acquired with Cirrus SD‐OCT in 99 controls, 99 EG, and 50 severe glaucoma (SG) patients. S/I Avg and N/T Avg RNFL, T Avg and N Avg GCIPL thicknesses were also calculated. AUCs were obtained for each parameter. ANCOVA was used to study the changes occurring to couples of rNFL/GCIPL sectors according with VFMD. RNFL and GCIPL sectors were compared normalizing the raw values to their sector's dynamic range [the interval between mean sector thickness in controls (max) and minimum sector thickness in SG (floor)], using the following equation: (sector thickness–floor)/(max–floor). The relationship between VFMD and S RNFL/ST GCIPL or I RNFL/IT GCIPL normalized thicknesses was investigated with linear regression analysis. Results GCIPL and RNFL sectors were thinner in EG and SG than controls (ANOVA, p < 0.001). In the EG group T Avg GCIPL was thinner than N Avg GCIPL (p < 0.001). S/I Avg rNFL had a higher AUC compared to Tot Avg (p = 0.001) and N/T Avg rNFL (p < 0.001). Similarly, T Avg GCIPL had a higher AUC (0.936) compared to Tot Avg GCIPL (p = 0.019) or N Avg GCIPL (p < 0.001). T Avg and N Avg GCIPL slopes against VFMD were significantly different (p < 0.001) in EG (VFMD ≥–6 dB), but not in SG (VFMD <–6 dB, p = 0.79). In EG, the slopes against VFMD were not statistically different for ST GCIPL vs. S RNFL (p = 0.258) and for IT GCIPL vs. I RNFL (p = 0.164). Conclusions Temporal macular GCIPL thinning is a hallmark of early glaucomatous damage along with S/I peripapillary RNFL thinning. Conversely, nasal GCIPL sectors are relatively spared in EG, resembling a pattern of damage more typical of N/T peripapillary RNFL