Evaluating Refractive Errors

Before recommending refractive surgery, your provider will conduct a thorough examination in order to evaluate your vision and check for any diseases of your eyes. This exam will include a series of tests designed to evaluate your refractive errors, and to determine which, if any, refractive surgery may best treat your condition.

The exam will be painless, although it may take some time and require some patience. Typically, your provider may shine bright lights into your eyes and ask you to look through a variety of different lenses as you read from a chart.

In most cases, your provider will conduct an external eye exam, where he will check your eyes using a light to make sure that the exterior parts are working properly. Your provider will check the position and movement of your eyes, confirm that your pupils respond normally, and check the appearance of your cornea.

An eye muscle test is used to confirm that your eye muscles are working properly. Your provider may ask you to use your eyes to follow an object, such as a pen. This test helps your provider detect any problems with the muscles that control eye movement.

A visual acuity test measures how sharply or clearly you can see something at a distance. Your doctor will ask you to identify different letters of the alphabet off a chart that is usually placed 20 feet away from you. The lines of type get smaller as you move down the chart. You cover one eye and read aloud, then cover the other eye and read aloud again. Your doctor monitors how well you can identify the letters and the result is stated as a fraction. This is where the term 20/20 vision comes from. The top number is the distance from you to the eye chart, and the bottom number is the distance at which a person with normal vision can correctly read the smallest line that you can read. For example, if a person's visual acuity is determined to be 20/50, that person can read at a distance of 20 feet what a person with normal vision can read at a distance of 50 feet.

Along with these standard eye tests, there are also a variety of other tests, including refraction assessments, visual field tests, slit lamp and retinal examinations, along with corneal topography and tests for glaucoma. The results of each test are important in helping your provider evaluate a different aspect of your vision.

Your provider will decide which tests will best help to evaluate your specific condition and refractive errors. Depending on the tests required, some providers will ask you to stop wearing your contact lenses for a certain amount of time prior to your evaluation.