What Is The Global Burden Of Visual Impairment?

According to the World health Organization (WHO), approximately 160 million people globally have visual impairment, 37 million of whom are blind and an additional 124 million of whom have low vision (defined as visual acuity ranging from 6/18 to 3/60). This estimate of visual impairment is based on best-corrected visual acuity and therefore misses any cases of visual impairment based on uncorrected refractive error. The purpose of this study was to calculate the global prevalence of visual impairment when visual impairment due to uncorrected refractive error was taken into consideration. Recent studies that assessed presenting visual acuity and estimated the contribution of uncorrected refractive error were examined. Of the 283 studies reviewed for potential inclusion in this meta-analysis, only 9 met the inclusion criteria. When data assessing visual impairment due to uncorrected refractive error were taken into account, the estimated prevalence of visual impairment rose from 161 million to 259 million, with 98 million cases of visual impairment (including 5 million cases of blindness) missed by the WHO estimate. Further, the contribution of uncorrected refractive error to estimates of visual impairment was greater in developing regions than in developed areas. The results of this study suggest that the actual worldwide prevalence of blindness is substantially higher than previously thought. Underestimation of visual impairment can lead to poor planning of interventions such as Vision 2020, and the contribution of uncorrected refractive error should be taken into account.