Characterization of Wedge-Shaped Defects in Prelaminar Tissue in Eyes With Primary Open Angle Glaucoma

Abstract

Purpose: To identify the functional and clinical significance of prelaminar wedge defects (PLWDs) detected by swept source optical coherence tomography (SS-OCT) in patients with primary open angle glaucoma (POAG). Methods: This is a prospective, cross-sectional study of patients with POAG and PLWDs, patients with POAG and no PLWDs, and age-matched healthy control subjects. Imaging was performed with SS-OCT (Topcon DRI Swept Source OCT) and spectral-domain OCT. POAG patients with severe glaucoma indicated by Humphrey Visual Field Mean Deviation <-12 dB or history of penetrating glaucoma surgery, and eyes with significant non-glaucomatous optic nerve abnormalities were excluded. PLWDs were defined as lesions where the curve and smooth delineation of the cup contour is lost and a triangular (wedge-shaped) defect can be outlined in the prelaminar layer (Figure 1) and were identified on radial and 5-line cross scans by two observers masked to diagnosis. Two-sided t-test, analysis of variance with Bonferonni correction, and multivariate logistic regression analysis adjusting for systemic and ocular characteristics were performed. Results: 16 POAG patients with PLWDs, 24 POAG patients without PLWDs, and 23 control patients were enrolled in the study. PLWDs were found in 40.0% of POAG patients vs. 8.7% of control subjects (p= 0.018). Of the POAG patients with PLWDs, 9 (56.3%) had subsequent imaging, all of which showed persistent PLWDs. POAG patients with and without PLWDs had similar HVF MD (-5.8 ± 5.0 dB vs. -4.8 ± 4.9 dB, p= 0.55). Paracentral loss on HVF was present in 56.3% of POAG with PLWDs and 33.3% of POAG without PLWDs (p= 0.20). POAG patients with PLWDs had more frequent history of disc hemorrhage (DH) than POAG patients without PLWDs (p=0.04). In the multivariate analysis, POAG patients with PLWD were younger in age (p=0.03) and had increased odds of having a history of DH (odds ratio= 14.1, p=0.02) compared to POAG patients without PLWD after adjusting for gender (p=0.37), VF MD (p=0.20) and maximum IOP (p=0.14). Conclusion: Wedge-shaped defects in the prelaminar tissue are found more frequently in eyes with POAG than control subjects. These defects are associated with younger age and a history of DH. These structural changes may represent a distinct pattern of damage in glaucoma and may potentially represent an optic nerve phenotype associated with a distinct POAG subset.