BACK TOTOP Browse A-ZSearchBrowse A-ZABCDEFGHIJKLMNOPQRSTUVWXYZ0-9 E-mail FormEmail ResultsName:Email address:Recipients Name:Recipients address:Message: Print-FriendlyBookmarksbookmarks-menuRefractionEye exam - refraction; Vision test - refraction; RefractionA refraction is an eye exam that measures a person's prescription for eyeglasses or contact lenses. How the Test is Performed This test is performed by an ophthalmologist or optometrist. Both of these professionals are often called an "eye doctor."You sit in a chair that has a special device (called a phoroptor or refractor) attached to it. You look through the device and focus on an eye chart 20 feet (6 meters) away. The device contains lenses of different strengths that can be moved into your view. The test is performed one eye at a time.The eye doctor will then ask if the chart appears more or less clear when different lenses are in place.The results depend on your responses. Then, a device shines specialized light into your eyes and also determines your refraction. Responses from you are not needed. Each type of refraction have their own benefits. How to Prepare for the Test If you wear contact lenses, ask the doctor if you need to remove them and for how long before the test. How the Test will Feel There is no discomfort. Why the Test is Performed This test can be done as part of a routine eye exam. The purpose is to determine whether you have a refractive error (a need for glasses or contact lenses).Routine eye examA standard eye exam is a series of tests done to check your vision and the health of your eyes.ImageRead Article Now Book Mark Article For people over age 40 who have normal distance vision but difficulty with near vision, a refraction test can determine the right power of reading glasses. Normal Results 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 (6/6).A value of 20/20 (6/6) is normal vision. This means you can read 3/8-inch (1 centimeter) letters at 20 feet (6 meters). A small type size is also used to determine normal near vision. What Abnormal Results Mean You have a refractive error if you need a combination of lenses to see 20/20 (6/6). Glasses or contact lenses should give you good vision. If you have a refractive error, you have a "prescription." Your prescription is a series of numbers that describe the powers of the lenses needed to make you see clearly.If your final vision is less than 20/20 (6/6), 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 (abnormally curved cornea causing blurred vision) AstigmatismAstigmatism is a type of refractive error of the eye. Refractive errors cause blurred vision. They are the most common reason why a person goes to ...ImageRead Article Now Book Mark Article Hyperopia (farsightedness) HyperopiaFarsightedness is having a harder time seeing objects that are close than things that are far away. The term is often used to describe the need for r...ImageRead Article Now Book Mark Article Myopia (nearsightedness) MyopiaNearsightedness is when light entering the eye is focused incorrectly. This makes distant objects appear blurred. Nearsightedness is a type of refr...ImageRead Article Now Book Mark Article Presbyopia (inability to focus on near objects that develops with age) PresbyopiaPresbyopia is a condition in which the lens of the eye loses its ability to focus. This makes it hard to see objects up close.ImageRead Article Now Book Mark Article Other conditions under which the test may be performed:Corneal ulcers and infections Corneal ulcers and infectionsThe cornea is the clear tissue at the front of the eye. A corneal ulcer is an open sore in the outer layer of the cornea. It is often caused by inf...ImageRead Article Now Book Mark Article Loss of sharp vision due to macular degeneration Macular degenerationMacular degeneration is an eye disorder that slowly destroys sharp, central vision. This makes it difficult to see fine details and read. The diseas...ImageRead Article Now Book Mark Article Retinal detachment (separation of the light-sensitive membrane (retina) in the back of the eye from its supporting layers) Retinal detachmentRetinal detachment is a separation of the light-sensitive membrane (retina) in the back of the eye from its supporting layers.ImageRead Article Now Book Mark Article Retinal vessel occlusion (blockage in a small artery that carries blood to the retina) Retinal vessel occlusionRetinal artery occlusion is a blockage in one of the small arteries that carry blood to the retina. The retina is a layer of tissue in the back of t...ImageRead Article Now Book Mark Article Retinitis pigmentosa (an inherited disorder of the retina)Retinitis pigmentosaRetinitis pigmentosa is an eye disease in which there is damage to the retina. The retina is the layer of tissue at the back of the inner eye. This...ImageRead Article Now Book Mark Article Risks There are no risks with this test. Considerations You should have a complete eye examination every 3 to 5 years if you have no problems. If your vision becomes blurry, worsens, or if there are other noticeable changes, schedule an exam right away.After age 40 (or for people with a family history of glaucoma), eye exams should be scheduled at least once a year to test for glaucoma. Anyone with diabetes should also have an eye exam at least once a year.GlaucomaGlaucoma is a group of eye conditions that can damage the optic nerve. This nerve sends the images you see to your brain. Most often, optic nerve da...ImageRead Article Now Book Mark Article People with a refractive error should have an eye exam every 1 to 2 years, or when their vision changes.Open ReferencesReferencesChuck RS, Dunn SP, Flaxel CJ; American Academy of Ophthalmology Preferred Practice Pattern Committee, et al. Comprehensive adult medical eye evaluation preferred practice pattern. Ophthalmology. 2021;128(1):1-29. www.aaojournal.org/article/S0161-6420(20)31026-5/fulltext. Published November 12, 2020.Chuck RS, Jacobs DS, Lee JK; American Academy of Ophthalmology Preferred Practice Pattern Refractive Management/Intervention Panel, et al. Refractive errors & refractive surgery Preferred Practice Pattern. Ophthalmology. 2018;125(1):1-104. PMID: 29108748 pubmed.ncbi.nlm.nih.gov/29108748/.Fu D, Ding X, Shang J, Yu Z, Zhou X. Accuracy of WASCA aberrometer refraction compared to manifest refraction and cycloplegic refraction in hyperopia measurement. Transl Vis Sci Technol. 2020;9(11):5. PMID: 33101782 pubmed.ncbi.nlm.nih.gov/33101782/.Wu A. Clinical refraction. In: Yanoff M, Duker JS, eds. Ophthalmology. 5th ed. Philadelphia, PA: Elsevier; 2019:chap 2.3.AllVideoImagesTogNormal vision - illustration Normal vision occurs when light is focused directly on the retina rather than in front or behind it.Normal visionillustrationNormal vision - illustration Normal vision occurs when light is focused directly on the retina rather than in front or behind it.Normal visionillustration Tests for Refraction RefractionRelated Information Vision problems(Symptoms)Corneal ulcers and infections(Condition)Age-related macular degeneration(Condition)Retinal detachment(Condition)Retinal artery occlusion(Condition)Retinitis pigmentosa(Condition) Review Date: 3/2/2021 Reviewed By: Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. 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