Grading system prospectively identifies patients at risk of developing ectasia

By assessing the asymmetry of the cylinder in addition to other ocular parameters, clinicians can have a more accurate picture of the patients who will and will not develop ectasia after LASIK, said Elias Zaidman, MD, of Cirugia y Medicina de Los Ojos, Mastic, Mexico.

"Until now, ectasia has been studied retrospectively," Dr. Zaidman said. "We propose prospectively studying our patients who are candidates for surgery. We are using a set of parameters that we think will identify patients who are at risk of developing ectasia."

He cited the study of Tabbara et al. as the basis for this study. The authors in that study established a grading system ranging from 1 to 3 and used the following parameters in a retrospective analysis of LASIK patients: keratometry, oblique cylinder, pachymetry, posterior surface elevation, the difference between the inferior and superior dioptric power, and the posterior best fit sphere and the anterior best fit sphere.

Dr. Zaidman has taken this assessment one step further by adding the asymmetry of the cylinder to his analysis of patients' eyes.

Dr. Zaidman showed in a series of patients that by adding asymmetry to his evaluation he was able to identify patients who should not have undergone refractive surgery, despite that fact that they appeared to be candidates without an assessment of the asymmetry of the cylinder.

"Ignoring the asymmetry would mean operating on a patient who should not have undergone surgery," he said.

"The indications for surgery have definitely become stricter," Dr. Zaidman concluded. "Had I known what I know now, I would not have caused two cases of ectasia. For the past 9 years, none of my patients has developed ectasia. By carefully studying patients, clinicians can predict those who will develop ectasia."