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