Tuesday, 17 July 2012

The refraction eye test

The refraction test 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 "the eye doctor."
You are asked to sit in a chair that has a special device (called a phoroptor or refractor) attached to it. You then look straight through that device and focus on an eye chart which is 20 feet away. The refractor contains lenses of different strengths that can be placed between you and the eye chart. This test is performed one eye at a time.
The eye doctor performing the test will ask if the chart appears more or less clear when different lenses are in place.

How to prepare for the test

If you wear contact lenses, ask the eye doctor if you need to remove them before the test and for how long do you need to keep them out.

How taking this test will feel like

You will experience absolutely no discomfort during this test, so you don’t need to worry about feeling any type of pain.

Why the test is performed

The refraction test can be done as part of a routine eye exam. The purpose of this test is to determine whether you suffer from any type of refractive error (that might require you to wear glasses or contact lenses).
If you are over the age of 40 and have normal distance vision, but you experience difficulty with near vision, a refraction test can determine the right diopter for reading glasses.

Normal results

If your vision (without glasses or contact lenses) is normal, then the refractive error is zero and this means that your vision should be 20/20.
20/20 is the numerical value for a perfect vision and this means that you are able to read 3/8-inch letters from a distance of 20 feet. A smaller sized font is also used to determine normal near vision.

What if the results are not normal?

You might suffer from a refractive error if you need a combination of lenses or glasses to achieve 20/20 vision. However, glasses or contact lenses should give you good vision.
The overall score you achieve during the refraction test is called the visual acuity test.
Abnormal results may indicate that you have either:

  • Astigmatism
  • Hyperopia (farsightedness)
  • Myopia (nearsightedness)
  • Presbyopia (inability to focus on near objects; this particular condition develops with age)


There are no risks involved in taking this test.


You should undergo a complete eye examination every 3 - 5 years even if you don’t suffer from any eye conditions, just to be sure that you still don’t have any problems. But if your vision becomes blurry, worsens, or if there are other noticeable changes, schedule an eye examination immediately.
After the age of 40 (or if you have a family history of glaucoma), eye examinations should be scheduled at least once a year to test for glaucoma. Anyone with diabetes should also undergo an eye exam at least once a year.

People who suffer from any refractive errors should have an eye examination every 1-2 years, or whenever their vision changes. Also, it’s always good to know that besides contact lenses, another option is Miami refractive surgery, especially if you don’t want to be bothered with wearing glasses.

No comments:

Post a Comment