Background Road traffic injuries are a major public health concern and their prevention requires concerted efforts. We aimed to systematically analyse the current evidence to establish whether any aspects of vision, and particularly interventions to improve vision function, are associated with traffic safety outcomes in low-income and middle-income countries (LMICs). MethodsWe did a systematic review and meta-analysis to assess the association between poor vision and traffic safety outcomes. We searched MEDLINE, Embase, PsycINFO, CINAHL, Web of Science, Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials in the Cochrane Library from database inception to April 2, 2020. We included any interventional or observational studies assessing whether vision is associated with traffic safety outcomes, studies describing prevalence of poor vision among drivers, and adherence to licensure regulations. We excluded studies done in high-income countries. We did a meta-analysis to explore the associations between vision function and traffic safety outcomes and a narrative synthesis to describe the prevalence of vision disorders and adherence to licensure requirements. We used random-effects models with residual maximum likelihood method. The systematic review protocol was registered on PROSPERO, CRD-42020180505. Findings We identified 49 (1•8%) eligible articles of 2653 assessed and included 29 (59•2%) in the various data syntheses. 15 394 participants (mean sample size n=530 [SD 824]; mean age of 39•3 years [SD 9•65]; 1167 [7•6%] of 15 279 female) were included. The prevalence of vision impairment among road users ranged from 1•2% to 26•4% (26 studies), colour vision defects from 0•5% to 17•1% (15 studies), and visual field defects from 2•0% to 37•3% (ten studies). A substantial proportion (range 10•6-85•4%) received licences without undergoing mandatory vision testing. The meta-analysis revealed a 46% greater risk of having a road traffic crash among those with central acuity visual impairment (risk ratio [RR] 1•46 [95% CI 1•20-1•78]; p=0•0002, 13 studies) and a greater risk among those with defects in colour vision (RR 1•36 [1•01-1•82]; p=0•041, seven studies) or the visual field (RR 1•36 [1•25-1•48]; p<0•0001, seven studies). The I² value for overall statistical heterogeneity was 63•4%.Interpretation This systematic review shows a positive association between vision impairment and traffic crashes in LMICs. Our findings provide support for mandatory vision function assessment before issuing a driving licence.

Background: Road traffic injuries are a major public health concern. The burden and road traffic fatality rate are especially high in low-and middle-income countries and the socioeconomic impact is profound. Although many authors have studied the correlation between vision and traffic safety, there is no robust evidence base that could be used in advocacy. This systematic review will test the hypothesis that interventions to improve vision function are associated with good traffic safety outcomes.Methods: Cochrane guidance on conducting a systematic review and Preferred Reporting Items for Systematic Review and Meta-Analysis - Protocols (PRISMA-P) were used to inform the preparation of this protocol and the Cochrane guidance and the main PRISMA guidance will inform the conduct and reporting of the review. We will search MEDLINE (Ovid), EMBASE (Ovid), PsycINFO (Ovid), CINAHL (EBSCO host), Web of Science, Cochrane Database of Systematic Reviews (CDSR) and The Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library. We will include studies of any design which either attempt to access traffic safety outcomes of any kind among persons with any vision deficit or examine vision among persons who use roads. The primary outcome for this review is any measure of traffic safety or surrogate outcomes. Study selection, data extraction and evaluation of risk of bias will be done by two reviewers. A meta-analysis or narrative data synthesis will be conducted, depending on study quality and homogeneity.Discussion: The results of this review will include summary estimates of vision and the effects of interventions to improve vision function, that are associated with traffic safety outcomes in LMICs. This systematic review will fill a gap in the evidence base with policy implications that will be useful for a wide audience and may improve vision of the drivers in LMICs, leading to better traffic safety outcomes.