What Is A Refraction Eye Exam?

A refraction eye exam is used to measure a prescription for a person’s contact lenses or eyeglasses. These tests also go by the name of vision test – refraction, eye exam – refraction, and just refraction.

How Is A Refraction Eye Exam Performed?

These tests are performed by either an optometrist or ophthalmologist. Both professionals are also called eye doctors. The test involves a refractor or phoropter that is attached to a chair. The patient sits in the chair and then looks through this device, focusing on the eye chart that is positioned 20 feet away. These devices contain lenses that come in different strengths that are moved into the patient’s view. The ophthalmologist or optometrist asks their patient whether the eye chart appears less or more clear with each lens.

Why Is This Test Performed?

These tests are typically performed with routine eye examinations. The aim is to find out whether the person has a “refractive error”, which means the patient needs contact lenses or glasses. For anyone over the age of 40 that has normal distant-vision, but they have difficulties with near-vision, refraction tests are often used to determine the correct reading glasses (the power).

What Are Normal Results?

When the person’s uncorrected vision (without contact lenses or glasses) is normal, the refractive-error will be zero (Plano), which means the person’s vision will be 1.0 or 20/20.

What Do Abnormal Results Mean?

If a person has a “refractive error” they will need more than one lens to clearly see 1.0 or 20/20. Contact lenses or glasses should improve the person’s vision. If a person has a “refractive error”, they have a “prescription”. The prescription makes up a number series that will describe the lens power required to make the person see clearly.

If the person’s “final vision” is under 1.0 or 20/20, even when using lenses, then there may be a non-optical issue with their eye. Vision levels that are achieved during refractions tests are called BCVA, which stands for best-corrected visual acuity.

An abnormal result might be caused by:

  • Hyperopia, better known as farsightedness
  • Astigmatism, which involves a cornea that is abnormally curved which causes blurred vision
  • Presbyopia, where the person is unable to focus on nearby objects. This condition typically develops as a person starts to age
  • Myopia, better known as nearsightedness

It is advisable to go for complete eye examinations every 3 to 5 years for those with no problems. If a person’s vision starts to get blurry or worsens, an exam should be scheduled right away.

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