Contrast sensitivity and stereoacuity predict road traffic accidents among drivers in Ghana: a case-control study

Road traffic accidents (RTAs) are a growing public health concern across sub-Saharan Africa, including Ghana. While human error is the leading cause, the role of visual function is often overlooked. This study investigates the relationship between visual function and accident involvement among drivers in Cape Coast, Ghana.

A comparative cross-sectional study involving 242 licensed drivers (121 cases, 121 controls) was conducted at the School of Optometry and Vision Science Eye Clinic, University of Cape Coast. Drivers aged 18 years and older were included in the study. Visual assessments included visual acuity, contrast sensitivity, stereoacuity, colour vision, visual fields, and refractive error. Data were analysed using the Wilcoxon rank sum test, Fisher's Exact Test, and multivariate logistic regression.

Mean age was comparable between groups (cases: 39 ± 11 years; controls: 39 ± 12 years). Drivers with accident history demonstrated significantly poorer stereoacuity (9.9% vs. 3.3%, p = 0.020) and contrast sensitivity (7.4% vs. 0.8%, p = 0.022). Visual acuity showed no significant difference (p = 0.6). Multivariate logistic regression showed that contrast sensitivity (1.75 ± 0.16 vs. 1.80 ± 0.11; p = 0.022) and stereoacuity (113.55 ± 89.18 vs. 87.77 ± 40.28 arcsec; p = 0.020) were the independent predictors of accident involvement, with ROC analysis showing poor discriminatory power (AUC = 0.635) for contrast sensitivity.

Contrast sensitivity and stereoacuity were independently associated with RTAs among drivers in Cape Coast. These findings suggest that assessments of contrast sensitivity and stereoacuity may provide useful complementary information beyond conventional visual acuity testing.