Global Magnitude of Visual Impairment Caused by Uncorrected Refractive Errors in 2004/prevalence Mondiale Des Deficiences Visuelles Dues a Des Defauts De Refraction Non Corriges En 2004/magnitud Mundial De Las Discapacidades Visuales Por Defectos De Refraccion No Corregidos En 2004

Introduction Refractive errors (myopia, hyperopia and astigmatism; presbyopia is not included in this study given the present paucity of data, but it is recognized that uncorrected, it could lead to an impaired quality of life) affect a large proportion of the population worldwide, irrespective of age, sex and ethnic group. Such refractive errors can be easily diagnosed, measured and corrected with spectacles or other refractive corrections to attain normal vision. If, however, they are not corrected or the correction is inadequate, refractive errors become a major cause of low vision and even blindness (for a selection of studies, see http://ftp. who.int/nmh/references/RE-estimatesreferences.pdf). Visual impairment from uncorrected refractive errors can have immediate and long-term consequences in children and adults, such as lost educational and employment opportunities, lost economic gain for individuals, families and societies, and impaired quality of life. Various factors are responsible for refractive errors remaining uncorrected: lack of awareness and recognition of the problem at personal and family level, as well as at community and public health level; non-availability of and/or inability to afford refractive services for testing; insufficient provision of affordable corrective lenses; and cultural disincentives to compliance. The definition of visual impairment in the International statistical classification of diseases, injuries and causes of death, 10th revision (ICD-10), H54, is based on vision, i.e. visual acuity obtained with the best possible refractive correction. (1) However, to assess the extent of visual impairment caused by uncorrected refractive errors, estimates need to be based on vision, i.e. visual acuity obtained with currently available refractive correction, if any. Thus, presenting vision, as opposed to best-corrected vision, provides the prevalence of visual impairment that could be improved simply by appropriate corrective refraction. Basing the definition of visual impairment on presenting vision extends the current definition to one that characterizes visual impairment faced by people in day-to-day activities. Using best-corrected vision, visual impairment was estimated to affect 161 million people globally in 2002, of whom 37 million were blind. (2) The main cause of blindness and low vision was cataract; however, it was recognized that unless uncorrected refractive errors were included among the causes, visual impairment at global level was significantly underestimated. This paper presents the estimate of the prevalence of visual impairment from uncorrected refractive errors for all ages over 5 years at regional and global levels, based on recent published and unpublished surveys. Some results from this paper were reported in a WHO press release on 11 October 2006 to mark World Sight Day. (3) Methods Definitions Presenting vision is defined by the visual acuity in the better eye using currently available refractive correction, if any. Best-corrected vision is the visual acuity in the better eye achieved by subjects tested with pinhole or refraction. Visual impairment caused by uncorrected or inadequately corrected refractive errors is defined as visual acuity of less than 6/18 in the better eye that could be improved to equal to or better than 6/18 by refraction or pinhole, thus spanning the low vision and blindness categories as currently defined in the ICD-10. It should be noted that in the revision of the ICD-10 categories of visual impairment proposed in 2003 by a WHO consultation on the development of standards for characterization of vision loss, low vision is replaced by two categories: moderate visual impairment (presenting visual acuity less than 6/18 but equal to or better than 6/60) and severe visual impairment (presenting visual acuity less than 6/60 but equal to or better than 3/60). …