The Association between Retinal Nerve Fibre Layer Thickness and Myopia in a Black South African Population

Abstract

Background: Myopia is a prominent cause of visual impairment worldwide. While optical coherence tomography (OCT) consistently measures the thickness of the retinal nerve fibre layer (RNFL), recognising irregularities in RNFL for eyes with high myopia is complicated by a high rate of false positive diagnoses for optic nerve diseases, primarily glaucoma. Aim: This study compared the RNFL thickness in African myopic eyes to non-myopic eyes and compared the RNFL thickness in different degrees of myopia in the same demographic group. Setting: The outpatient department of St John Eye Hospital is the ophthalmology department of Chris Hani Baragwanath Academic Hospital in Johannesburg, South Africa. Methods: A cross-sectional study of a black ethnical South African population comparing retinal nerve fibre layer thickness between a myopic group and their healthy non-myopic counterparts. One hundred and thirty nine eyes of 139 patients were enrolled in the study. Results: Participants were separated into a control group (n=68) and a myopic group (n=71). The participants in this study had a mean age (SD) of 48.1(16.2) years. The average RNFL thickness in the non-myopic group (107.1µm) was substantially thicker compared to the myopic group (98.1µm) (p=0.003). The average RFNL thickness in the high myopic group was 16.0μm lower compared to the low myopic group (p<0.001). The findings from the multivariate regression analysis in this study indicate that average RNFL thickness is significantly affected by both axial length (p <0.001) and age (p=0.017). Conclusion: This study's findings indicate that non-temporal RNFL thickness is reduced in a myopic South African population of black ethnicity compared to the non-myopic control group from the same demographic. Additionally, it demonstrates that the high myopic group has thinner RNFL than the low myopic group.