CLINICAL QUERIES: Assessing visual acuity

August 2010 
Volume 40  Number 8
Pages 65 - 65
  PDF Version Available!

How do I accurately assess an adult's visual acuity?—K.H., W.VA.Jan Cannon, MSN, RN, replies: The Snellen eye chart is commonly used to measure visual acuity.1 It consists of a series of block letters or letters and numbers, which become progressively smaller with each descending line. At one end of each line are two numbers that indicate the visual acuity associated with that line. The first number indicates the distance of the patient from the chart, and the second indicates the distance at which a normal eye can read that line of letters. For example, visual acuity of 20/50 means that at 20 feet the patient can read print that a person with normal vision could read at 50 feet. The larger the second number, the worse the vision. "20/40 corrected" means the patient could read the 40 line wearing glasses or contact lenses (a correction).Start by obtaining a health history to determine whether the patient has medical conditions that can affect vision, such as eye infections, diabetes,

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