Discrepancy in Loss of Macular Perfusion Density and Ganglion Cell Layer Thickness in Early Glaucoma

Purpose To identify characteristics of patients with early open-angle glaucoma exhibiting greater macular perfusion density (PD) loss compared with macular ganglion cell layer (GCL) thickness loss. Design Cross-sectional study. Methods Optical coherence tomography (OCT) imaging of the optic nerve head and macula was conducted in patients and healthy control subjects. Minimum rim width, retinal nerve fiber layer and GCL thickness, and PD from OCT angiography were derived. Only high-quality images were included. For direct comparison, raw PD and GCL thickness values in patients were converted to relative age-corrected loss values based on data from controls. Demographic and ocular variables related to greater PD loss compared with GCL thickness loss were identified with multivariate logistic regression. Results Data from 89 patients (median mean deviation with the 24-2 and 10-2 tests, Humphrey Field Analyzer: −1.96 dB and −1.49 dB, respectively) and 54 controls were analyzed. Sixty-three (71%) patients had relatively more GCL thickness loss, whereas 26 (29%) had relatively more PD loss. More PD loss was associated with lower OCT and OCT-angiography signal strength (odds ratio [95% confidence interval], 0.64 [0.40, 0.96] and 0.60 [0.38, 0.86], per dB, respectively), thicker retinal nerve fiber layer thickness (1.08 [1.01, 1.16] per μm), and female sex (6.57 [1.25, 48.79]). Conclusion Less than one-third of patients with early glaucoma had more loss of perfusion compared with conventional structural loss in the macula. Even within a range of high-quality images, lower signal strength may be at least partially responsible for apparent perfusion loss.