Purpose: To determine factors that predispose of the development of corneal ectasia after LASIK.

Method: 56 eyes in 35 patients were studied. The patients had been operated on over the past 5 years in either South Africa or the United States of America.

Results: Latent kerataconus is a definite contradiction for lamellar surgery. Predisposing factors such as corneal thickness less than 500 microns, corneal curvature greater than 48.5 dioptres, minor corneal irregularity and most importantly, re-operations were discussed. 7 idiopathic cases are described where no obvious etiology could be found.

Conclusion: Keratectasia is an important and dangerous complication of LASIK. Latent kerataconus, thin corneas and re-operations are important predisposing factors. There is concern that the incidence may increase as larger treatment zones are attempted.