Best-corrected visual acuity of 20/200 (6/60) or worse in the better eye In the United States, Canada and most European countries, this is defined as: The legal definition of blindness varies slightly from country to country. Vision2020 is a global iniative to eliminate avoidable causes of sight loss worldwide. The eye is considered to be completely not working if it cannot perceive any light that is directly shone at it.
A bright light is shone on to the eye and the patient is asked if any light is noticed. Light perception is used when vision is worse than counting fingers. One or two fingers are placed 1 meter in front of the patient, and the patient is asked to count the number of fingers that are shown. When the vision is so poor that the Snellen chart cannot be used for visual acuity testing, then it can be estimated with counting fingers at 1 meter. The ‘normal’ visual acuity is 6/6 or 20/20.Ħ/6: seeing at 6 meters what the average person sees at 6 metersĢ0/20: seeing at 20 feet what the average person sees at 20 feetĦ/18: seeing at 6 meters what the average person sees at 18 metersĢ0/60: seeing at 20 feet what the average person sees at 60 feetĦ/60: seeing at 6 meters what the average person sees at 60 metersĢ0/200: seeing at 20 feet what the average person sees at 200 feetģ/60: seeing at 3 meters what the average person sees at 60 metersĢ0/400: seeing at 20 feet what the average person sees at 400 feetġ/60: seeing at 1 meters what the average person sees at 60 metersĢ0/1200: seeing at 20 feet what the average person sees at 1200 feet These criteria are based upon testing of the vision with the Snellen chart.With the standard Snellen chart, vision is tested at a distance of 6 meters or 20 feet. WORLD HEALTH ORGANIZATION (WHO) DEFINITION Category This definition is internationally accepted and incorporated into the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10).
The standard definitions from the World Health Organization (WHO) are listed in the table below. It is the worst outcome of any eye disease. It does not necessarily have to mean not being able to see absolutely anything at all. Blindness is essentially the inability to see well enough to be able to have a reasonable quality of life.
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