Myopic macular Bruch's membrane defects

Abstract

AbstractPurpose: To examine peculiarities of macular Bruch's membrane defects (BMD) in axially elongated eyes.Methods: Using light microscopy, enucleated human globes were histomorphometrically.Results: The study included 247 eyes (axial length: 20.0–37.0 mm). BMDs were detected in 15 (6.1%) eyes (axial length: 30.6 ± 2.4 mm) (1.9 ± 0.9 BMD/eye with BMDs), located in the macular region in 10 eyes. Mean BMD size was 1.93 ± 1.62 mm (range: 0.22 mm–6.24 mm). Prevalence and size of BMDs were associated with longer axial length (OR: 1.52; p = 0.001) and higher prevalence of scleral staphyloma (OR: 16.3; p < 0.001). BMD width was smaller than the defect width in the overlying retinal pigment epithelium (RPE) layer (p = 0.003) and larger than the length of a defect in the overlying inner nuclear layer (0.43 ± 0.76 mm; p = 0.008) and the width of an inner limiting membrane bridge (0.13 ± 0.33 mm; p = 0.001). Choriocapillaris thickness (8.8 ± 5.0 μm vs. 7.9 ± 3.2 μm; p = 0.94), BM thickness (3.1 ± 0.6 μm versus 3.0 ± 0.5 μm; p = 0.43) and RPE cell density (31.6 ± 8.4 cells/480 μm vs. 27.4 ± 8.8 cells/480 μm; p = 0.051) did not differ significantly between the region at the BDM margin and neighbouring regions. The sclera was thinner in the BDM region than in the neighbouring regions (0.28 ± 0.19 mm vs. 0.36 ± 0.13 mm; p = 0.006).Conclusions: BMDs as hallmark of myopic macular degeneration are characterized by a larger defect in the overlying RPE layer, smaller defects in the overlying retinal outer nuclear layer and inner nuclear layer, localized scleral thinning and an association with scleral staphylomas. Thickness of the choriocapillaris and density of the RPE cell layer, both absent within the BDMs, do not differ between the BMD margin and neighbouring regions. The results suggest an association between BDMs and absolute scotomas, stretching of the overlying retinal nerve fiver layer, an axial elongation‐associated stretching effect as aetiology of the BDMs, and a biomechanical role BM may play.