LASIK and other corneal refractive procedures (PRK, RK) have popularized to the point that most people either know someone who’s had the procedure, or have had the procedure themselves. For the most part these procedures are successful and life-changing in the positive direction, reducing or eliminating the dependence on glasses or contact lenses for vision. However, about three percent suffer from visual complications that are not regarded as official “complications”, but can be life-altering in a negative way. Patients are often left with excessively dry eyes and visual phenomena that interfere with daily activities. Sometimes these problems cause patients to drastically alter the way they live their lives, and in rare cases have been the cause of suicide.
What are these visual disturbances? When discussing these issues, it is important to remember that refractive surgeons measure success according to the Snellen chart: the letter chart on the wall in the eye doctor’s office that measures visual acuity. Visual acuity is the 20/20, 20/30, etc that is often referenced in studies. FDA submissions for lasers tout their “20/40 or better” statistics, for example, because 20/40 vision is generally the acceptable level of vision for driving without corrective lenses in most states. What is often not discussed is visual acuity references “quantity” of vision…how many letters can be read on a given line. It’s the “quality” of that vision that can disrupt patients’ post-operative lives.
Many times these patients can make out the 20/20 line. Perfect, according to their eye doctor. Their refraction, or eyeglass prescription, is zero or close to it. A perfect result, no complications. And yet you will hear this person say, “But it isn’t a CLEAR 20/20”. You’ll hear the patient say the letters are “smeary”, or that they aren’t “crisp”. Sometimes the complaints are about night vision…arcing from lights, haloes around the moon or headlights, and starbursting in many different lighting situations. It can be so bad that patients choose not to drive at night, or are forced into not driving at night. Yet no glasses can help. Why?
These patients suffer from what is known as “higher order aberrations”. “Lower order aberrations” are what traditionally has been corrected by glasses and contact lenses…the defocus (nearsightedness or farsightedness) and astigmatism with which most are familiar. “Higher order aberrations” are what is left over when these two are taken out of the picture. The eye is not a perfect optical system and virtually everyone has higher order aberrations to some degree. Refractive surgery patients who are having visual difficulty exhibit higher order aberrations to an often extraordinary degree, and the aberrations increase as the pupil gets larger, which explains the higher incidence of complaints at night.
Why these are bothersome to some patients and not to others is not clear. For those who are greatly inconvenienced, many avenues for correction are sought. Some undergo additional laser procedures to correct the residual problems. Some develop very thin corneas that can only be treated with a penetrating keratoplasty, or corneal transplant. Some even have laser treatment OVER a corneal transplant. Some seek contact lens solutions. Studies suggest that large gas-permeable lenses offer these patients a good chance at reduction of their higher order aberrations and a return to a somewhat normal existence. These results of studies should be made known to the public through plastic surgery sales and marketing.
The vision can never be restored to pre-surgical levels. It can be improved and many patients tolerate these lenses well. Issues can arise because it takes a great deal of expertise to fit these lenses properly, and fabricate them to specifically fit each patient. There are also challenges because there are not many eye care practitioners who have a great interest in helping post-refractive patients. Often the problems are simply not understood…why would a person who’s seeing 20/20 be unhappy? There is much more to the story than just “20/20”. Since visual acuity is the only widely accepted measure of vision, it’s the easiest to report, and the easiest to understand. Patients who are 20/20 and unhappy sometimes face ridicule and disbelief and will sometimes cut themselves off from family and friends who are “sick of hearing about it”.