title: The global burden of visual difficulty in low, middle, and high income countries.
abstract: OBJECTIVE
  Using a world-wide, population-based dataset of adults, we sought to determine the frequency of far visual difficulty and its associated risk factors.
  
  
  METHODS
  The World Health Survey (WHS) was conducted in 70 countries throughout the world in 2003 using a random, multi-stage, stratified, cluster sampling design of adults ages 18 years and older. Far vision was assessed by asking "In the last 30 days, how much difficulty did you have in seeing and recognizing a person you know across the road (i.e. from a distance of about 20 meters)?". Responses included none, mild, moderate, severe, or extreme/unable. The income status of countries was estimated using gross national income per capita data from 2003 from the World Bank. Prevalence and regression estimates were adjusted to account for the complex sample design.
  
  
  RESULTS
  21% of adults reported any visual difficulty. The rate varied by the income status of the country with the percentage who had any visual difficulty being 24%, 23%, and 13% in low, middle, and high income countries, respectively. Five percent of people reported severe or extreme visual difficulty with rates in low, middle, and high income countries of 6%, 5%, and 2% respectively. Risk factors for visual difficulty included older age, female sex, poorer socioeconomic status, little to no formal education, and diabetes (P<0.05).
  
  
  CONCLUSIONS
  One out of five adults in the WHS reported some degree of far visual difficulty. Given the importance of vision to living an independent life, better access to quality eye care services and life course factors affecting vision health (e.g. repeated eye infections, diet lacking vitamin A) must receive adequate attention and resources, especially in low and middle income countries.
authors.affiliation: Department of Ophthalmology, Université de Montréal, Montreal, Quebec, Canada. eefreeman@gmail.com
authors.forename: Ellen E
authors.initials: EE
authors.lastname: Freeman
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Roy-Gagnon
authors.forename: Elodie
authors.initials: E
authors.lastname: Samson
authors.forename: Slim
authors.initials: S
authors.lastname: Haddad
authors.forename: Marie-Josée
authors.initials: MJ
authors.lastname: Aubin
authors.forename: Claudia
authors.initials: C
authors.lastname: Vela
authors.forename: Maria Victoria
authors.initials: MV
authors.lastname: Zunzunegui
mesh_terms: D000328:Adult; D019049:Developed Countries; D003906:Developing Countries; D014943:Global Health; D006306:Health Surveys; D006801:Humans; D007182:Income; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D014786:Vision Disorders / Q000453:epidemiology*; D055815:Young Adult