The global burden of trachomatous visual impairment .2. Assessing burden

This paper builds on results of a previous paper on the prevalence of trachomatous visual impairment as the foundation for assessing the global burden of trachomatous blindness and low vision: approximately 2.9 million cases of trachomatous blindness and 3.8 million low visioned corresponding to a global prevalence of trachomatous visual impairment equal to 1.3/1,000 in 1990 was estimated. For each visually impaired person, the years of life lost due to premature mortality and the years lived in a handicapped state are added to yield a single measure of disease burden called handicap adjusted life years (HALYs). Age, gender and visual acuity group specific HALYs are multiplied by the prevalence of trachomatous visual impairment to yield an estimate of the global burden of trachoma visual impairment equal to 80 million HALYs. Analysis of the distribution of the global burden by age, gender, visual acuity and region provide direction for trachoma research and programme priorities. Sensitivity analysis reveals that the burden estimates of trachomatous visual impairment may vary from as low as 15 million to as high as 500 million HALYs. Given this degree of variability, burden comparisons with other blinding and non-blinding conditions for the purposes of identifying health sector priorities may be misleading.