This study indicates that visual impairment in 2010 is a major health issue that is unequally distributed among the WHO regions; the preventable causes are as high as 80% of the total global burden.

Objectives: Trachoma is the leading cause of infectious blindness worldwide. It is known to be highly correlated with poverty, limited access to healthcare services and water. In 2003, the WHO estimated that 84 million people were suffering from active trachoma, and 7.6 million were severely visually impaired or blind as a result of trachoma: this study provides an updated estimate of the global prevalence of trachoma based on the most recent information available. Methods: A literature search of recent published and unpublished surveys in the 57 endemic countries was carried out: the result of surveys that used the WHO trachoma grading system and additional information from regional and country experts served as a basis to determine the prevalence of trachoma in each country. Results: Population-based surveys provided recent information for 42 out of 57 endemic countries. 40.6 million people are estimated to be suffering from active trachoma, and 8.2 million are estimated to have trichiasis. Conclusions: The current estimate of prevalence of trachoma is lower than the previous WHO estimates: this can be explained by the success in implementing control strategy, by more accurate data, as well as by socioeconomic development in endemic countries.

Two-hundred-and-eight population-based studies on visual impairment for 68 countries are reported in detail, providing an up-to-date, comprehensive compilation of the available information on visual impairment and its causes globally.

A data bank of prevalence of hearing impairment for monitoring and implementation of programmes at national or global level and for the estimate of the global burden has been established. A systematic search was conducted of random-sample population-based studies of bilateral hearing impairment with clearly defined hearing threshold levels. Fifty-three studies from 31 countries from all WHO regions were found to meet the selection criteria. The prevalence of mild and disabling hearing impairment and other details from the studies are reported by WHO region. Although a large number of studies were found, only a small number among them were suitable surveys of prevalence of bilateral hearing impairment in the general population. Hearing impairment is a major disability that should be monitored at all ages: more population-based surveys are needed in all regions of the world. Utilization of the WHO protocol is recommended for collection and analysis of data in standard ways; especially recommended is the use of WHO threshold levels and to report the prevalence of bilateral impairment, both of which required to calculate burden.

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