Evaluating Refractive Errors


Lt Col Reynolds
Before recommending refractive surgery, a provider will conduct a thorough examination in order to evaluate vision and check for any diseases of the eyes. This exam will include a series of tests designed to evaluate refractive errors and screen for eye disorders, and to determine which, if any, refractive surgery may best treat the patient’s condition. Dr. Flemings, can you tell us more about this exam?

Lt Col Flemings
Sure, Dr. Reynolds. The exam is typically painless, but it may take some time and require some patience. In most cases, providers will conduct an external eye exam, where they will check the eyes using a bright light to check the position and movement of each eye, confirm that the pupils respond normally, and examine the appearance of the cornea.

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

A visual acuity test measures how sharply or clearly a person can see something at a distance. The provider will ask the patient to identify different letters of the alphabet from a chart that is usually placed 20 feet away. The size of each line of letters gets smaller as you move down the chart.

The patient covers one eye and reads the smallest line they can see, and then repeats with the other eye. The provider monitors how well the patient can identify the letters, and the result is recorded as a fraction.

This is where the term “20/20 vision” comes from. The top number represents the distance from the patient to the eye chart. The bottom number represents the distance at which a person with normal vision can correctly read the smallest line read by the patient. 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.