Comparison of Structural and Functional Features in Primary Angle Closure and Open Angle Glaucomas

Abstract

Précis: Using a large data set, we showed structural and functional differences between primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG). Primary angle closure glaucoma has relative structural preservation and worse functional loss inferiorly. Purpose: To identify structural and functional differences in PACG and POAG. Materials and Methods: In this large cross-sectional study, differences in structural and functional damage were assessed among patients with POAG and PACG with optical coherence tomography and reliable visual field testing. Results: In all, 283 patients with PACG and 4110 patients with POAG were included. Despite similar mean deviation on visual fields (mean [SD] –7.73 [7.92] vs. –7.53 [6.90] dB, P=0.72), patients with PACG had thicker global retinal nerve fiber layer (RNFL), smaller cup volume, smaller cup-to-disc ratio, and larger rim area than POAG (77 [20] vs. 71 [14] µm, 0.32 [0.28] vs. 0.40 [0.29] mm3, 0.6 [0.2] vs. 0.7 [0.1], 1.07 [0.40] vs. 0.89 [0.30] mm2, P<0.001 for all), while patients with POAG had more pronounced inferior RNFL thinning (82 [24] vs. 95 [35] µm, P<0.001). In a multivariable analysis, hyperopia [odds ratio (OR): 1.24, confidence interval (CI): 1.13–1.37], smaller cup-to-disc ratio (OR: 0.69, CI: 0.61–0.78), thicker inferior RNFL (OR: 1.15, CI: 1.06–1.26) and worse mean deviation (OR: 0.95, CI: 0.92–0.98) were associated with PACG. Functionally, POAG was associated with superior paracentral loss and PACG with inferior field loss. After adjusting for average RNFL thickness, PACG was associated with more diffuse loss than POAG (total deviation differences 1.26–3.2 dB). Conclusions: Patients with PACG had less structural damage than patients with POAG despite similar degrees of functional loss. Regional differences in patterns of functional and structural loss between POAG and PACG may improve disease monitoring for these glaucoma subtypes.