PURPOSE: Ectasia after laser in situ keratomileusis (LASIK) is a rare but 
serious complication. Prevention includes proper patient selection with 
detection of those at particular risk. Causes of ectasia include predisposition, 
excessive ablation with less than 250 microm of residual stromal bed, thicker 
than normal flap, irregular corneal thickness, and different ablation rates.
METHODS: We evaluated corneal curvature patterns and their relationship to 
corneal topography and pachymetry maps.
RESULTS: Corneal topography (axial, tangential, and altimetric) and pachymetry 
map characteristics of normally astigmatic corneas, keratoconus, false-positive 
and false-negative cases, as well as contact lens-induced warpage are discussed.
CONCLUSIONS: Preoperative pachymetry maps for LASIK surgery allow accurate case 
selection through detection of borderline cases, and provide important 
documentation of preoperative status, as well as useful information for 
improving surgical strategy. Another important parameter is the asphericity 
index.