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Visual Acuity

Visual acuity is a measure of how well a person can focus on an object. To test visual acuity, the person may read letters or symbols on a chart from the top down, line by line, covering first one eye and then the other.

A visual acuity score is a ratio comparing the person's performance to that of people who have "normal" vision.

For example, a person who can read what people with normal vision can read at 20 ft (6 m) has 20/20 (6/6) distance vision. The larger the second number, the worse the vision.

  • If vision is 20/40 (6/12), the person can read at 20 ft (6 m) what people with normal vision can read at 40 ft (12 m).
  • If vision is 20/60 (6/18), the person can read at 20 ft (6 m) what people with normal vision can read at 60 ft (18 m).

By Healthwise Staff
Primary Medical Reviewer Kathleen Romito, MD - Family Medicine
Specialist Medical Reviewer Christopher J. Rudnisky, MD, MPH, FRCSC - Ophthalmology
Current as of May 29, 2013

WebMD Medical Reference from Healthwise

Last Updated: May 29, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.