Ganglion Cell Complex Thickness and Macular Vessel Density Loss in Primary Open-Angle Glaucoma

Purpose: To characterize the change rate of ganglion cell complex (GCC) thickness and macular vessel density in healthy, preperimetric glaucoma and primary open-angle glaucoma (POAG) eyes. Design: Prospective, longitudinal study. Participants: One hundred thirty-nine eyes (23 healthy eyes, 36 preperimetric glaucoma eyes, and 80 POAG eyes) of 94 patients who had at least 3 visits were included from the Diagnostic Innovations in Glaucoma Study. The mean follow-up was 2.0 years for healthy eyes, 2.6 years for preperimetric glaucoma eyes, and 2.6 years for POAG eyes. Methods: OCT angiography (OCTA)-based vessel density and OCT-based structural thickness of the same 3x3-mm(2) GCC scan slab were evaluated. The dynamic range-based normalized rates of vessel density and thickness change were calculated and compared within each diagnostic group. The association between the rates of thickness and vessel density change and potential factors were evaluated. Main Outcome Measures: The rates of GCC thinning and macular vessel density loss. Results: Significant rates of GCC thinning and macular vessel density decrease were detectable in all diagnostic groups (all P < 0.05). In healthy eyes and preperimetric glaucoma eyes, the normalized rates of GCC thinning and macular vessel density decrease were comparable (all P > 0.1). In contrast, the normalized rate (mean, 95% confidence interval) of macular vessel density decrease in the POAG eyes (-7.12 [-8.36, -5.88]%/year) was significantly faster than GCC thinning (-2.13 [-3.35, -0.90]%/year; P < 0.001). In the POAG group, more than two thirds of the eyes showed faster macular vessel density decrease than GCC thinning; faster macular vessel density decrease rate was associated significantly with worse glaucoma severity (P = 0.037). The association between GCC thinning rate and glaucoma severity was not significant (P = 0.586). Intraocular pressure during follow-up significantly affected the rate of GCC thinning in all groups (all P < 0.05) but showed no association with the rate of macular vessel density decrease. Conclusions: Both GCC thinning and macular vessel density decrease were detectable over time in all diagnostic groups. In POAG eyes, macular vessel density decrease was faster than GCC thinning and was associated with severity of disease. Macular vessel density is useful for evaluating glaucoma progression, particularly in more advanced disease.