Online circular contrast perimetry performed in glaucoma patients in Sub-Saharan Africa: a multi-centre comparative study in Nigeria.

BACKGROUND/OBJECTIVES: Online circular contrast perimetry (OCCP) provides visual field testing on any computer or tablet, without additional hardware. Its performance has not been evaluated in an African cohort. This study compared the performance of OCCP to standard automated perimetry (SAP) in a cohort of Nigerian patients with glaucoma. SUBJECTS/METHODS: Across 404 patients (198 males, 206 females), OCCP mean deviation (MD) and pattern standard deviation (PSD) were compared with SAP using paired analyses, Bland-Altman plots, intraclass correlation coefficients (ICC) and Pearson correlation. The correlation between MD and vertical cup-to-disc ratio (VCDR) was assessed using linear regression. Reliability indices, including fixation losses (FL), false positives (FP), and false negatives (FN), were also compared. RESULTS: Mean OCCP MD was higher than SAP in both eyes (p < 0.001). Bland-Altman analysis demonstrated a positive bias toward higher MD values with OCCP (1.09-1.53 dB), while ICCs indicated moderate reliability and correlation with SAP (0.52-0.53). MD showed stronger correlations with VCDR for OCCP than for SAP (r = -0.41 to -0.48 vs -0.32 to -0.41), although these differences were not statistically significant. Mean PSD values were similar between devices with minimal bias (-0.10 to -0.16 dB); however, agreement and correlation were poor (ICC 0.39; r = 0.39-0.40). Reliability indices (FL, FP, FN) were comparable between OCCP and SAP. CONCLUSIONS: OCCP demonstrates consistent moderate agreement with SAP for MD, with similar reliability. As a potential screening and surveillance tool, OCCP could be used to substantiate visual field testing in SSA, especially where perimetry availability is limited.