BACKGROUND: LASIK (Laser in situ keratomileusis) is used in refractive surgery 
especially for correction of higher degrees of myopia. Preservation of Bowman's 
layer as well as less postoperative pain and the slight to absent subepithelial 
haze are regarded as advantages compared to photorefractive keratectomy (PRK). 
However, numerous serious complications have been described in the literature.
PATIENTS AND METHODS: LASIK treatment was performed elsewhere in two patients to 
treat myopia or myopic astigmatism between -6 and -9 diopters (D). An 
astigmatism of -6 D was corrected with the LASIK method in another patient with 
keratoconus. Progressive corneal ectasia of up to seven diopters occurred in all 
four eyes within a few months.
CONCLUSION: Corneal ectasia can occur after LASIK even in low degrees of myopia 
of less than ten diopters. Recently, -12 D has been specified as the upper limit 
for this technique. It is especially important to rule out an early keratoconus 
or a forme fruste of keratoconus preoperatively since keratectasia with 
particularly rapid progression can occur in such cases: we would like to 
designate this as "malignant keratoconus".