Axial Elongation in Myopia May Contribute to Bruch Membrane Defects

Bruch membrane defects (BMDs) may result from axial elongation-associated changes occurring in patients with myopia, according to research published in Heliyon. Longer gaps in the retinal pigment epithelium (RPE), smaller gaps in the inner and outer nuclear layers, scleral thinning, and scleral staphylomas are associated with these defects, the report shows.  

Researchers performed a histologic assessment of 247 enucleated eyes (mean age, 61.9 years; 54.7% men) obtained from individuals with axially elongated globes (mean axial length, 25.2 mm). The team identified the presence, number, location, and length of BMDs and examined correlations between these defects and other ocular parameters associated with myopic axial changes.

A total of 6.1% of eyes (n=15) had BMDs — 10 within the macular region. Individuals with BMDs were older (mean age, 68.2 years) and the prevalence and size of these defects were associated with longer axial length (odds ratio [OR], 1.52; 95% CI, 1.19-1.94; P =.001) and a higher prevalence of scleral staphylomas (OR, 16.3; 95% CI, 2.67-99.3; P <.001), the report shows. 

The mean size of the largest BMD per eye was 1.93 mm, which was significantly shorter than the length of the gap in the RPE layer on top of it (2.61 mm; P =.003) and longer than the length of the gap in the adjacent inner nuclear layer (0.43 mm; P =.008). Scleral thinning occurred more in the BMD area compared with the adjacent areas (0.28 vs 0.36 mm; P =.006). 

“[H]ighly myopic eyes can show RPE defects in the macular region in the absence of BMDs, however all BMDs are accompanied by a (larger) RPE defect,” according to the researchers. “It has remained unclear whether the RPE defects led to the BMDs or whether both, the RPE defects and the BMDs, were the results of the same pathomechanism which could be an axial elongation-induced increased strain in the RPE layer and in BM.”

Study limitations include potential confounding due to ocular diseases and the strict inclusion of individuals of European descent.