Refractive errors, including nearsightedness, farsightedness, and astigmatism, are the main eye conditions that send people to the optometrist.
What is a refraction test?
A refraction test is performed by an optometrist during an eye exam to determine the refractive condition of the eye and the corrective lens prescription needed to compensate for any refractive errors.
Reasons for refraction testing
Refraction testing is performed during an eye exam if a patient is unable to see clearly and needs corrective lenses. Retinoscopy is often performed first to confirm the type of refractive errors causing vision problems. Refraction testing is then performed to determine the lens power needed to compensate for refractive errors so that light comes to a sharp focus on the retina. This information is used then to prescribe corrective lenses, such as eyeglasses and contacts. For patients interested in contact lenses, a contact lens fitting may be required as well.
How refraction testing is performed
An optometrist performs refraction using a mechanical device called a phoropter, which consists of several different lenses. Using the phoropter, the optometrist places lenses of various powers in front of your eyes while you look through the lenses at an eye chart. The optometrist then uses either a hand-held tool called a retinoscope or a computerized instrument to measure how each of the lenses focus the light in order to determine which lens power is needed to compensate for your refractive errors.
During the examination, the optometrist may also ask you which lens helps you to see the eye chart more clearly. For patients who are unable to respond, the optometrist may use eye drops to dilate the eyes before the procedure. This prevents the eyes from changing focus and can help the optometrist in determining the most appropriate lens prescription.
If you have noticed a change in your vision, you may be in need of a new prescription and can benefit from refraction testing. Schedule an appointment with your optometrist today to have your vision checked.