Grading system may help predict post-LASIK corneal ectasia risk

A new grading scale may provide surgeons with a simple, reproducible method for determining which patients are at risk for developing corneal ectasia after LASIK, according to a study.

Khalid F. Tabbara, MD, and Amgad A. Kotb, MD, of the Eye Center in Riyadh, Saudi Arabia, developed the system and tested its efficacy in a retrospective study. The researchers reviewed records for 37 LASIK patients who developed corneal ectasia and compared their findings to a control group of 111 LASIK patients who did not develop ectasia.

All patients underwent pre- and postoperative corneal topographic analyses measuring six factors linked to corneal ectasia: keratometry, oblique cylinder, pachymetry, inferior and superior corneal dioptric power, posterior surface elevation, and the ratio of posterior to anterior best sphere fit. Each factor was assigned a value of 1 to 3 points, with higher values indicating a greater risk of ectasia. The researchers then totaled each point value to estimate patients' cumulative risk scores.

The researchers found that corneal ectasia developed in all patients with a score over 12, in no patients with a score below 7 and in 59% of patients with a score between 8 and 12.

Some patients with post-LASIK corneal ectasia showed no evidence of preoperative forme fruste keratoconus, the authors noted. As this is a common indicator of postoperative complications, this finding emphasizes the need for detailed screening, they said.

While the authors suggested that the scale could be incorporated into computerized systems, it "does not replace a meticulous eye examination, family history and determination of the corneal status before refractive surgery," they said. Larger studies are needed to further test its predictability, they added.

The study is published in the September issue of Ophthalmology.