Numerous risk factors found for corneal ectasia after LASIK

San Francisco-Knowledge about risk factors for corneal ectasia after LASIK is increasing, and some of the risk factors may be very subtle. R. Doyle Stulting, MD, PhD, described some of these risks factors during Cornea Day 2006 at the annual meeting of the American Society of Cataract and Refractive Surgery.

Since post-LASIK ectasia was first reported in 1998, about 14 cases have been reported in the English-language literature; that number may increase. Dr. Stulting reported a series of cases (10 eyes of seven patients) after LASIK in 2003.

These candidate risk factors for the development of ectasia were validated by comparison to a series of patients who underwent successful LASIK-all three were found to be significant discriminators, said Dr. Stulting, professor of ophthalmology and director, Cornea and External Disease Service, Emory University, Atlanta.

To validate these risk factors further, Dr. Stulting and his colleagues used a control population of patients with high myopia who had undergone successful LASIK. Again, the three candidate factors were confirmed risk factors for ectasia.

"These three factors-preoperative refractive pachymetry, presence of forme fruste keratoconus, and thin residual stromal beds-were significant discriminators with significant p values," he said.

Additional risk factors

Another logical question was whether ectasia developed in patients who had no risk factors. Dr. Stulting and colleagues solicited patients from three physician Internet groups from April to October 2003.

"Strict exclusion criteria were used to be certain that the patients had no currently recognized risk factors," he emphasized.

Of 27 eyes, nine met the study criteria. The mean patient age was 27.8 years, which is lower than that of a typical LASIK population. Ectasia has occurred after LASIK for the correction of hyperopia as well, Dr. Stulting said.

A previous study found that keratoconus can occur after severe eye rubbing. Dr. Stulting suggested that mechanical trauma is another risk factor for ectasia after LASIK. He also noted that a best spectacle-corrected visual acuity (BSCVA) worse than 20/20 with increasing astigmatism can be a risk factor for ectasia.

In addition, he presented a case of ectasia after LASIK in a patient with a family history of premature birth, trauma, and mild retinopathy of prematurity and wondered whether this history was contributory to the development of ectasia.

Dr. Stulting advised that surgeons not ignore possible "red flags," such as slightly asymmetric topography and increasing astigmatism, especially in a patient with more than one warning sign.

Some patients, Dr. Stulting warned, will develop ectasia despite normal topography and undergoing photorefractive keratectomy (PRK).

"Are biomechanical properties the missing risk factors?" he asked. "Were some patients destined to develop keratoconus later in life and just happened to undergo LASIK or PRK? Would some of these eyes have been considered normal without having undergone LASIK? Is this the explanation for the younger age of the patients who develop ectasia without any risk factors?"