Eye test - refraction; Vision test - refraction; Refraction

If your uncorrected vision (without glasses or contact lenses) is normal, then the refractive error is zero (plano) and your vision should be 20/20.

A value of 20/20 is perfect vision, meaning you are able to read 3/8-inch letters at 20 feet. A small type size is also used to determine normal near vision.

You have a refractive error if you need a combination of lenses to see 20/20. Glasses or contact lenses should give you good vision.

If your final vision is less than 20/20, even with lenses, then there is probably another, non-optical problem with your eye.

The vision level you achieve during the refraction test is called the best-corrected visual acuity (BCVA).

Abnormal results may be due to:

• Astigmatism
• Hyperopia (farsightedness)
• Myopia (nearsightedness)
• Presbyopia (inability to focus on near objects that develops with age)

Other conditions under which the test may be performed:

• Corneal ulcers and infections
• Macular degeneration
• Retinal detachment
• Retinal vessel occlusion
• Retinitis pigmentosa

Images

Normal vision

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Refraction test Overview

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Refraction 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)