Ophthalmologists debate whether ectasia is preventable

June 23, 2008

In a point-counterpoint debate at the annual meeting of the American Academy of Ophthalmology, one clinician contended that the rate of post-LASIK ectasia is declining and that, with careful screening and other preparatory steps, the rate of ectasia can be kept very low. The counter-argument by another clinician suggested that the multifactorial basis of ectasia as well as unknown risk factors make it impossible to prevent a certain percentage of cases from developing.

Key Points

New Orleans-Progressive post-LASIK keratectasia, although rare, can have severe consequences, and it would be in the best interest of patients as well as physicians to prevent it. But is prevention possible? In a debate at the American Academy of Ophthalmology annual meeting, David Huang, MD, PhD, claimed that ectasia is a preventable condition, whereas J. Bradley Randleman, MD, said that the multifactorial basis of ectasia makes it impossible to prevent in a certain percentage of cases.

"By very carefully screening patients preoperatively and performing intraoperative pachymetry, you can reduce the risk of ectasia to a very low level," said Dr. Huang, associate professor of ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles.

He noted that one surgeon had performed an analysis of nearly 9,700 cases of myopic LASIK and found that keratectasia had developed in none of them. At a 95% confidence interval, this risk works out to be less than 0.03%, which is lower than the risk of endophthalmitis and is similar to the risk of being injured in a car accident after driving 30,000 miles.

He also said that reports in the literature indicate a declining level of post-LASIK ectasia.

"There is no ticking time bomb there; instead, it's an ebbing tide. And there's no rising flood of secondary hyperopia and aberration as we saw in radial keratotomy. I think if you do things right-and more and more surgeons are doing these things right-the risk is getting very low," Dr. Huang said.

"If you do LASIK properly, the risk [of ectasia] is low," he continued. "We should not be scared of it, but we should be knowledgeable about how to interpret the risks. We always should do preoperative pachymetry. We should be vigilant and conservative, and we should keep up with new developments in diagnostic technology that could detect even earlier stages of forme fruste keratoconus, but there is no need for us to stop performing this miraculous procedure that has benefited a lot of our patients."

Opposing perspective

Presenting an opposing perspective, Dr. Randleman observed that only moderate consistency exists between preoperative screening methodologies currently in use and intraoperative incidents leading to corneal weakening and postoperative ectasia. The advent of new technologies should reduce but will not eliminate new cases, added the assistant professor of ophthalmology, section of cornea, external disease, and refractive surgery, Emory Eye Center, Atlanta.

The essence of the problem is that ectasia is multifactorial in development, with preoperative and intraoperative risk factors, Dr. Randleman said, adding that the condition also has arisen in many eyes with no apparent risk factors.

He described a stratified scoring system that he and colleagues designed that they hoped could improve the accuracy of predicting which patients were at risk of ectasia. This system assigned point values from 0 to 4 for different potential risk factors; the higher the cumulative score, the greater the risk of developing post-LASIK ectasia. This system retrospectively identified almost 93% of the patients who had developed ectasia as well as correctly categorizing 98.5% of controls as low-risk.

Although this scoring system was more reliable than a traditional form of risk analysis, it was not 100% accurate, Dr. Randleman said.

As further support for his contention that ectasia cannot be completely prevented at this time, he noted ongoing debate among experts over this condition.

"There are a variety of risk factors that are not agreed on and/or have not been validated," he said, adding that the many different topographic analysis systems may not produce identical results.

Intraoperative incidents leading to corneal weakening will be reduced but not eliminated in all cases, Dr. Randleman added. Variability in flap thickness still will occur with new devices such as the femtosecond laser, and variability in stromal bed thickness also will persist. In fact, individual variability may be one of the most significant factors associated with development of ectasia, he said.

Postoperatively, ectasia still will develop in some patients without risk factors or intraoperative incidents due to the natural progression of unidentified factors as well as to as-yet unidentified keratoconus.

Future developments that may further reduce the incidence of ectasia include enhanced corneal tensile strength measurement, advanced topographic analysis, and corneal hysteresis measurement, Dr. Randleman said.

It is unlikely that ectasia will completely cease to occur, but it also is important to remember that the development of ectasia does not, per se, constitute malpractice, he concluded.