Retinal Nerve Fibre Layer Thickness in Nigerians with Type 2 Diabetes: A Comparative Study in Kano, North West Nigeria

Structural retinal changes in diabetic patients can precede clinically visible retinopathy, and retinal nerve fibre layer (RNFL) thinning measured by optical coherence tomography (OCT) has emerged as an early biomarker of diabetic retinal neurodegeneration. This study compares RNFL thickness between type 2 diabetic patients without visible retinopathy and age-matched non-diabetic controls at Aminu Kano Teaching Hospital, Kano State, North West Nigeria. A cross-sectional comparative design will be employed, recruiting 120 diabetic patients and 120 controls matched for age, gender, and refractive error. Spectral-domain OCT will be used to measure peripapillary RNFL thickness in four quadrants (superior, inferior, nasal, temporal). Regression analysis will control for diabetes duration, HbA1c levels, intraocular pressure, and blood pressure. The study anticipates significantly thinner RNFL in diabetic patients compared to controls, particularly in the inferior and superior quadrants. Findings will contribute to the early biomarker literature for diabetic retinal neurodegeneration and will support advocacy for routine OCT screening in diabetic patients even in the absence of visible retinopathy. This research fills a critical gap in the quantitative retinal imaging literature from northern Nigeria and provides locally validated evidence for the early structural impact of diabetes on retinal architecture in the North West geopolitical zone. Keywords: retinal nerve fibre layer, OCT, type 2 diabetes, Kano, diabetic retinopathy