Macular Bruch's membrane defect and dome-shaped macula in high myopia

Purpose To examine an association between macular Bruch's membrane defects (MBMD) and a dome-shaped appearance of the macula (DSM). Design Retrospective, observational case series study. Methods The study included highly myopic individuals who were consecutively examined between May 2014 and December 2015. The patients underwent swept-source optical coherence tomography (OCT) for visualization of DSM and MBMDs defined as Bruch's membrane defects located at a distance of maximal 1500 mu m from the foveola. Results Out of 1983 highly myopic eyes (1057 patients), 166 eyes (8.4%; 95% confidence interval (CI): 7.2%, 9.6%)) showed a DSM and 534 eyes showed a MBMD. In multivariate binary regression analysis, higher prevalence of DSM was associated with a higher prevalence of a MBMD (P<0.001; OR: 1.96; 95% CI: 1.40, 2.75) after adjusting for longer axial length (P<0.001; odds ratio (OR): 1.27; 95% CI: 1.16, 1.38). In eyes with a DSM partially surrounded by a MBMD, the retina, retinal pigment epithelium (RPE) and choroid appeared relatively unchanged in the central region with Bruch's membrane (BM) preserved. In the ring-like BM-free region surrounding the central prominent island of the DSM, the RPE, the outer and middle retinal layers, the choriocapillaris and the middle-sized choroidal vessel layer were absent. In association with a DSM, three MBMD types were differentiated: MBMDs in patchy chorioretinal atrophy, MBMDs in choroidal neovascularization-related macular atrophy, and MBMDs as temporally extending large parapapillary gamma zone. Conclusions Presence of a DSM was significantly associated with the presence of MBMDs. The morphology of the DSM in association with MBMDs may be associated with a focal relaxation of the posterior sclera, no longer pushed outward by an expanding BM but allowed to partially bulge inward, leading to the formation of a DSM.