Purpose: To investigate whether macular perfusion density (PD) changes measured over time by optical coherence tomography angiography (OCTA) are detectable before progressive macular ganglion cell layer (GCL) thinning in early glaucoma.
Methods: This prospective longitudinal cohort study involved patients with early open-angle glaucoma and healthy subjects imaged by OCT and OCTA every 4 months. GCL thickness and macular PD were evaluated in 16 tiles in the macula. We estimated baseline percentage losses of GCL thickness or macular PD in glaucoma patients with age-corrected normative values derived from the healthy subjects. Additionally, the threshold slope separating glaucoma patients from healthy subjects with 90% specificity was used to determine the number of patients with steeper slopes than the threshold slope.
Results: Eighty patients with glaucoma and 42 healthy subjects were included. In eight tiles (50%), patients with a significant macular PD slope had a significantly greater baseline percentage loss of GCL thickness relative to macular PD compared to patients without a significant macular PD slope. Furthermore, in 15 tiles (94%), a greater baseline percentage loss of GCL thickness relative to PD was significantly correlated with faster PD slopes. In contrast, only one tile (6%) showed these significant trends for GCL slopes. The number of patients with faster GCL slopes than threshold slopes was significantly larger than patients with faster PD slopes in 12 tiles (75%).
Conclusions: A decrease in GCL thickness precedes a measurable decrease in macular PD. Early glaucomatous progression is more frequently detectable with changes in GCL thickness compared to macular PD.