First, let's start with some definitions. Myopia (nearsightedness) is a condition in which light rays are focused in front of the retina. This causes the axial length of the eye to increase, resulting in distant objects appearing fuzzy. Hyperopia (farsightedness) is a condition in which light rays are focused behind the retina, causing the axial length to shorten. Near objects then appear fuzzy. Astigmatism is where the curvature of the cornea is irregular, resulting in two images.

Now that we agree on the basics, lets move on to refractive surgery. The two types are radial keratotomy (RK) and PRK (photorefractive keratotomy). RK has been around for about 20 years. Small radial (spoke-like) incisions are made in the cornea resulting in reshaping and vision correction. PRK uses laser pulses to effectively do the same thing, but with more precision, and reportedly better results.

It is estimated that up to 80% of myopic patients may be candidates for PRK. The selection criteria include normal ocular health, age over 18, stable refractive error (no noticeable change in the last year), between 1.5 and 7.0 diopters of myopia, pupil size equal to or less than 6 mm (in room light).

There are some conditions that would preclude a patient from having this procedure to include collagen vascular diseases, ocular disease, systemic disease such as diabetes, history of side effects to steroids.

Is PRK safe for aviators? Pilots should be aware that clinical trials stating success rates of 90% or more, are based on vision correction to 20/40 or better, not 20/20 or better, uncorrected visual acuity.

Complications that can occur are long healing periods, pain, infection, glare, halos, starburst, under or over-correction, infection, corneal haze, cataracts, and reduced visual acuity in low light conditions.

PRK may be performed in one eye at a time. The FDA suggests a three-month interval between operations, giving time to see how the procedure works in one eye, prior to moving on to the second.

Predictability of the resulting refractive correction is less than exact, particularly for those with more severe myopia. This can lead to under/over correction of the refractive error. The premature need for using reading glasses occurs in 1-3 % of the cases.

The FAA will consider applicants with PRK once they are fully healed and stabilized, providing there are no adverse complications and all other visual standards are met. Pilots should be aware commercial airlines may have policies that consider refractive surgery as a disqualifying conditions. Such is also the case with the military and many private companies.

The majority of patients having undergone PRK have done quite well. The newest laser device called Lasik has reportedly advanced PRK another step forward.

If you are considering refractive eye surgery, contact your opthomologist for further information.

About the author...

Dr. Stephen W. Roberts, M.D., in addition to being a mult-engine, instrument rated private pilot, is also a Senior Aviation Medical Examiner for the Federal Aviation Administration. Dr. Roberts specializes in Aviation Medicine, and is considered by many to be an expert in his field, with over twelve years experience! He is also a member of the Civil Aviation Medical Association and the AOPA. He is truly an advocate of aviation medicine as well as general aviation. Dr. Roberts has also authored numerous articles in Air Progress magazine, and frequently lectures for the Department of Aviation at Mount San Antonio College.