Alternate Names: Eye test - refraction

How Performed: This test is performed in the ophthalmologist’s or optometrist’s (eye doctor’s) office. You sit in a chair that has a special device (phoropter or refractor) attached to it and look through the phoropter at an eye chart approximately 20 feet away. The phoropter contains lenses of different strengths that can be moved into view. The eye doctor will ask if the chart appears more or less clear with the lenses that are in place. The eye doctor can determine if you have myopia (nearsightedness), hyperopia (farsightedness), an astigmatism (asymmetrical cornea), or presbyopia (inability to focus on objects that are close to you). The extent of vision difficulty can be determined. The information obtained from a refraction test allows the prescription for eyeglasses or contact lenses to be correct for each person.

How To Prepare: Avoid eye strain the day of the test (read in adequate light, get plenty of rest the night before the test).

Discontinue contact lens use.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:

• preschooler test or procedure preparation (3 to 6 years)
• schoolage test or procedure preparation (6 to 12 years)
• adolescent test or procedure preparation (12 to 18 years)

How It Feels: There is no discomfort.

Risks: There are no risks.

Why Performed: This test can be done as part of a routine eye test to determine if a person has normal vision. When a person complains of blurred vision, this test can help determine the extent of poor vision. It can also be performed to help follow the progress of treatments or diseases of the eye.

Normal Values: 20/20 vision (perfect vision; able to read 3/8 inch letters at 20 feet)

Abnormal Results:

• myopia (nearsightedness)
• hyperopia (farsightedness)
• astigmatism (asymmetrical cornea)
• presbyopia (inability to focus on near objects that develops with age)

• corneal ulcers and infections
• macular degeneration
• retinal detachment
• retinal vessel occlusion
• retinitis pigmentosa

Cost:

Special Considerations: A complete eye examination should be done every 3 to 5 years if there are no problems. If vision becomes blurry, worsens, or if there are other noticeable changes, an eye examination should be scheduled immediately. After 40 years old (or for people with a family history of glaucoma), eye examinations should be scheduled more frequently to test for glaucoma.

People with refraction problems should have an eye examination every 2 to 3 years.