LASIK (laser-assisted in situ keratomileusis) surgery to improve visual acuity is a great boon to many; but, as with any surgery, there are risks and complications to consider.
The Post interviewed Dr. Ronald Krueger of the Cleveland Clinic Cole Eye Institute—a veteran of 18,000 refractive surgery procedures—about why vision sometimes gets worse after LASIK and how to avoid or treat this perplexing post-op problem.
To frame the discussion, however, let’s first take a quick look at the eye, specifically its outmost covering, the cornea, which provides two-thirds of the eye’s focusing power.
How well you see depends on the shape and curve of your cornea. A normal cornea is smoothly rounded with even curves from side to side and top to bottom. Vision problems—or refractive errors—affecting about 120 million people in the United States develop when the cornea becomes too curved (nearsightedness), too flat (farsightedness), or curves more in one direction than in another like the back of a spoon (astigmatism).
Eyeglasses and contacts correct refractive errors, but LASIK surgery is an increasingly popular option for convenience and comfort.
So, here’s the rub.
During LASIK, the surgeon creates a flap in the eye’s cornea and then uses a laser to reshape it for good vision correction, explains Dr. Kreuger. In a relatively few cases, the cornea weakens after surgery (a condition called ectasia) and loses its ability to maintain the desired shape. As a result, vision blurs and gradually deteriorates.
We asked Dr. Krueger to discuss the latest information about the symptoms and risks for post-LASIK ectasia, and new advances in what doctors can do when it occurs.
Post: What are the symptoms of post-LASIK ectasia?
Dr. Krueger: Patients with ectasia lose visual acuity—some immediately, others months or even years after the surgery. Images become distorted as the cornea loses its rounded shape, and most find they need new lenses or progressive glasses as those changes occur.
Post: How common is it?
Dr. Krueger: Post-LASIK ectasia parallels keratoconus, a naturally occurring condition in which, although no surgery has taken place, the structural integrity of the cornea is not maintained and begins to bulge in certain ways that distort vision. Probably one out of 2,000 people in the population have keratoconus.
LASIK-induced ectasia, while rare, is presumed to be more prevalent in people with subclinical keratoconus. In other words, patients with previously unrecognized corneal weakening may develop a more prominent problem after LASIK.
Post: Who is most at risk?
The most common risk factor is an irregularity on the corneal topography map, a tool we utilize to help screen out individuals who are not suitable candidates for LASIK surgery. As mentioned, having an irregular or steep cornea may be a telltale sign of subclinical keratoconus that may contribute to post-operative ectasia.
Surgeons also look very carefully at a risk score system that is based on published data collected over many years from large groups of patients who developed post-LASIK ectasia. In developing this system, investigators assigned a certain amount of risk to various factors. For example, corneal thickness less than A amount might have B amount of risk toward ectasia. A topography map showing C amount of irregularity may contribute D amount of risk. Being young presents more risk because the cornea gets a little stiffer with age. Then, they developed a way to tabulate an overall score from the list of individual risks.
While the scoring system is published and based on actual data, it has been criticized. Many patients who fit or exceed that score have done perfectly fine and never developed ectasia. But LASIK surgeons do consider this score before doing surgery in order to avoid this phenomenon.
Post: Are topography maps standard of care in LASIK surgery?
Dr. Kreuger: Yes. But they aren’t definitive. Surgeons have to consider other factors.
Post: Does ectasia usually show up in both eyes?
Dr. Kreuger: It can initially develop in one eye, but the potential could exist in both eyes.
Post: What can be done to help people with post-LASIK ectasia?
Dr. Kreuger: The primary treatment is contact lenses to provide a new, smooth shape for the eye to look through.
What has come along for keratoconus, and is showing benefit for post-LASIK ectasia, is a procedure called crosslinking. Collagen crosslinking is a photochemical method of applying vitamin B-2 (riboflavin) drops on the eye and then shining an ultraviolet light that activates the riboflavin to help create little links in the cornea that make it stronger. It is being used in countries around the world, and FDA trials are underway in the United States.
Post: So this is an experimental procedure at this point?
Dr. Kreuger: It’s an investigational procedure in the United States. But it has been investigated in other countries and has shown good success.
Post: Are corneal transplants an option?
Dr. Kreuger: In advanced cases, yes. A transplant will replace the irregular and weak cornea with a stronger one. Then, you can correct it. But that’s a pretty advanced procedure. Corneal transplants may also be considered when crosslinking is not a good option or has been tried and is not fully correcting the problem.
Post: What advice would you offer to people considering LASIK?
Dr. Kreuger: I would suggest several things: 1) Go to more than one place to have your eyes evaluated so that you can get a sense of what doctors are saying at one place versus another. 2) Do some homework so you can ask lots of questions. 3) Make sure you are going to a place that has a stellar reputation for eye care in general. 4) Find an experienced doctor who has good judgment and the patient’s best interests at heart. 5) Ultimately, find the latest technology. Sophisticated imaging devices are now available to help determine which eyes have any risk for keratoconus or ectasia. Hopefully, there will be even newer and better tools in the future.