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The Need for a Revised Approach to Epidemiological Monitoring of the Prevalence of Visual Impairment

99 The distribution of the leading causes of world blindness has evolved over the years. Available estimates of the causes of blindness throughout the world suggest a remarkable reduction in the proportion of blindness due to the causes of blindness most readily addressed through public health oriented programs, such as onchocerciasis, Vitamin A deficiency, and trachoma. 1,2 In contrast, conditions that require individual level ophthalmic services to prevent blindness—cataract, glaucoma, diabetic retinopathy and others—increasingly predominate as the major causes of blindness worldwide. 1 Scaling up of the training and retention of ophthalmologists may be the challenge of the day for the second decade of the Vision 2020 initiative and beyond. As we go forward, we will continue to require unbiased data regarding the major causes of blindness to evaluate where the problem of blindness stands and what progress is being made throughout the world. Kuper, Polack and Limburg, among others, have taken the lead in providing us with a valuable practical tool for assessing the prevalence of major blinding eye conditions, the Rapid Assessment of Avoidable Blindness (RAAB). 3 This approach makes the conduct of a population-based survey that is representative of a population achievable for a motivated ophthalmic leader, by providing software to walk the user through the statistical and epidemiological complexities which otherwise might shipwreck a noble vision to collect data regarding vision loss. Indeed, the number of surveys completed has expanded greatly since the RAAB methodology became available. Standardization of the method also provides interesting opportunities to combine (or compare) data across surveys in a sort of meta-analysis. For instance, pooling of these data potentially could be used to assess what the “other” causes of visual impairment are which in aggregate make up the second leading non-refractive cause of vision loss worldwide after cataract, 1 but which individually have a prevalence too low to estimate in a single survey of achievable scale. The downside of the approach is that the analytic methods are pre-specified, and users rely upon a fixed algorithm for determining the proportion of blindness attributable to various causes, based on the WHO/PBL Eye Examination Record (Version III) method endorsed in 1988 by WHO. This approach is “…not designed to collect information about every eye condition likely to be encountered in field sur veys. It provides for the recording of blinding eye conditions which are of public health significance.” 4 It may be time for a revision and/or clarification of