Retinal nerve fibre layer thickness values and their associations with ocular and systemic parameters in Black South Africans

Purpose: To measure the retinal nerve fibre layer (RNFL) thickness values and investigate their associations with other parameters in healthy eyes of Black South Africans. Methods: 600 participants with healthy eyes, of whom 305 (50.83%) were males and 295 (49.17%) were females, with a mean age of 28.15 ± 13.09 years, underwent a detailed ophthalmic examination. RNFL thickness was measured by iVue SD-OCT. Results: The mean global RNFL thickness was 110.01 ± 7.39 μm. The RNFL was thickest inferiorly (135.06 ± 9.66 μm) and superiorly (131.72 ± 10.46 μm), thinner nasally (87.24 ± 13.22 μm), and thinnest temporally (73.63 ± 15.66 μm). Multivariate analysis showed that thicker mean global RNFL thickness was significantly associated with younger age, shorter axial length (AL) and hyperopia (p < 0.001). Mean RNFL thickness decreased by approximately 0.11 μm per year of aging life, and by 1.02 μm for each 1-mm of axial elongation. There was a 0.62 μm RNFL thickness increase for every dioptre change in spherical power towards more hyperopia. Conclusion: Mean RNFL thickness values and their associations established in this population may be of clinical value when assessing factors that influence this parameter and diagnosing diseases affecting it. Keywords: Retinal nerve fibre layer, optical coherence tomography, refractive error, axial length, glaucoma