Developing a Nigerian Normative Database for Optical Coherence Tomography Parameters: A Multi-Centre Study Across the Six Geopolitical Zones

Optical coherence tomography (OCT) normative databases embedded in commercial instruments are derived predominantly from Caucasian and East Asian populations, limiting their clinical applicability in African populations with distinct ocular biometric characteristics. This study develops a comprehensive normative database for spectral-domain OCT parameters in ethnically Nigerian adults across all six geopolitical zones. A multi-centre cross-sectional design will recruit 1,800 healthy adults aged 18 to 70 years from 12 sites spanning the North East, North West, North Central, South East, South South, and South West zones. Inclusion criteria will exclude systemic and ocular disease, while participants will undergo high-definition peripapillary RNFL, macular ganglion cell complex, and optic disc parameter measurements using the Cirrus HD-OCT. A mixed-effects normative modeling framework will account for age, sex, ethnicity, axial length, and signal strength. The study will produce age-stratified and sex-stratified normative reference ranges specific to the Nigerian population. This pioneering research addresses a fundamental limitation in current glaucoma diagnostics and diabetic retinopathy monitoring in Nigerian clinical practice, where foreign normative comparisons generate false positives and negatives. The normative database will be open-access and integrated into glaucoma screening programs nationally. Findings will be presented to the Federal Ministry of Health and professional eye care bodies for adoption into national clinical guidelines. Keywords: OCT normative database, Nigerian population, retinal nerve fibre layer, multi-centre, glaucoma diagnostics