Careful screening needed, but not foolproof for avoiding post-LASIK ectasia

November 10, 2007

Careful screening is important for identifying LASIK candidates potentially at risk for postoperative ectasia. Surgeons also need to realize there are likely several unknown risk factors for this potentially devastating outcome, said Marcelo V. Netto, MD, at Refractive Surgery Subspecialty Day.

Careful screening is important for identifying LASIK candidates potentially at risk for postoperative ectasia. Surgeons also need to realize there are likely several unknown risk factors for this potentially devastating outcome, said Marcelo V. Netto, MD, at Refractive Surgery Subspecialty Day.

"There is good consensus that preoperative corneal topographic abnormalities, corneal thickness, residual stromal thickness, and patient age are important risk factors for ectasia," said Dr. Netto, department of ophthalmology, University of São Paulo, Brazil. "However, this event is probably less iatrogenic than we think. Perhaps refractive surgeons should not feel so guilty when it occurs, because it appears some patients are genetically predisposed to develop ectasia post-LASIK even in the absence of any identifiable risk factors and even without laser surgery."

In a recently completed study, Dr. Netto reviewed the charts of more than 10,000 patients who had undergone laser refractive surgery. Fifteen eyes were identified that developed ectasia, although 30% of the total series had no further follow-up.

While three of the 15 cases occurred in eyes determined to have subclinical keratoconus preoperatively, nine (60%) involved eyes without any evident risk factor. The series included eyes that had undergone hyperopic LASIK or PRK for low myopia. Also surprising from the review was the finding that ectasia never occurred in a number of eyes that had several preoperative risk factors and long-term, postoperative follow-up of up to 10 years.

In addition to evaluating patients for accepted probable risk factors, other possible risk factors may be sought in the history-taking or by using new technologies. Patients should be asked about any habit of eye rubbing or whether they have relatives with keratoconus. Additional measurements to consider include posterior corneal surface and corneal thickness maps as well as corneal biomechanical properties (Ocular Response Analyzer, Reichert). However, Dr. Netto cautioned further study is needed to establish the utility of these assessments as ectasia screening tools.