Avoidable visual impairment due to uncorrected refractive error in Nakuru county, Kenya: evidence from a large community-based cross-sectional study of over 5,000 participants

Uncorrected refractive error is the leading cause of distance visual impairment (VI) globally and is largely preventable. In sub-Saharan Africa, data on presenting and residual VI after refractive correction are limited, restricting the assessment of refractive services. This study estimated the prevalence of presenting and residual VI, the avoidable burden due to URE, and age-, sex-, and temporal trends in refractive error and presbyopia in Kenya. We conducted a cross-sectional study using convenience sampling to recruit participants. Data were obtained from three annual community-based eye screening programs conducted between 2023 and 2025 in Nakuru County, Kenya, each involving clinical eye examinations. Participants underwent standardised assessments of monocular and binocular distance and near visual acuity, and anterior/posterior segment examination. Objective and subjective refraction (without cycloplegia) was performed only in participants whose unaided distance visual acuity was worse than 6/9 in the better-seeing eye ( n = 2,306). VI was classified using World Health Organization (WHO) criteria, and refractive error as myopia ( ≤ − 0.50 DS), hyperopia ( ≥ + 0.50 DS), and astigmatism which was defined as a cylindrical refractive error of ≥ 0.75 D in magnitude (i.e., cylinder power ≤ − 0.75 DC). Descriptive statistics summarised characteristics: chi-square tests and multivariable logistic regression assessed associations with demographics. Temporal trends were evaluated across the three years. A total of 5,096 participants (mean age 38.9 ± 20.6 years; 69.2% female) were included. Presenting distance VI affected 21.7% of participants, comprising predominantly mild and moderate impairment, while blindness was observed in 1.0%. Following refractive correction, VI decreased to 9.4%, whereas blindness changed minimally to 0.9%. Age was the strongest predictor of VI; children and youth had lower odds than older adults (AOR = 0.3; 95% CI: 0.2–0.4 and AOR = 0.4; 95% CI: 0.3–0.5, respectively). Refractive error was identified in 1,345 participants (58.3% of the 2,306 refracted; 26.4% of all 5,096 screened). Myopia was the most common refractive error (right and left eyes: 30.6% and 30.1% of participants refracted; 13.8% and 13.6% of all participants screened). Presenting VI increased from 22.4% in 2023 (n=2016) to a peak of 24.8% in 2024 (n=1346), before declining to 18.5% in 2025 (n=1734). Presbyopia was assessed and identified in 1,204 participants (mean age 54.8 ± 10.4 years; 73.8% female). Improvement in VI following optical correction was observed across all age groups, though less pronounced among older adults. Visual impairment affected approximately one in five participants, with a substantial proportion attributable to refractive error and reduced following optical correction. The findings highlight the potential contribution of refractive correction to reducing VI among individuals accessing community eye-care services.