Eye test - acuity; Vision test - acuity; Snellen test

Visual acuity is expressed as a fraction.

• The top number refers to the distance you stand from the chart. This is usually 20 feet.
• The bottom number indicates the distance at which a person with normal eyesight could read the same line you correctly read.

For example, 20/20 is considered normal. 20/40 indicates that the line you correctly read at 20 feet away can be read by a person with normal vision from 40 feet away.

Even if you miss one or two letters on the smallest line you can read, you are still considered to have vision equal to that line.

Abnormal results may be a sign that you need glasses or contacts, or it may mean that you have an eye condition that needs further evaluation by a health care provider.

Related topics:

• Astigmatism
• Farsightedness
• Nearsightedness
• Presbyopia

Images

Normal, near, and farsightedness

Eye

Visual acuity test

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Visual acuity test Overview

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Visual acuity test Risks

Review Date: 02/10/2011
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine; and Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)