Thin corneas: Risk factor for ectasia?

November 7, 2008

Scientific evidence does not support the hypothesis that thinner preoperative central corneas are an independent risk factor for postLASIK ectasia, said William B. Trattler, MD, director of cornea at the Center for Excellence in Eye Care, Miami. Eyes with a thin cornea (less than 500 µm) and normal topography are at no greater risk than those with thicker corneas of developing postoperative ectasia and may be biomechanically strong and similar to thicker corneas in their behavior, Dr. Trattler added.

Scientific evidence does not support the hypothesis that thinnerpreoperative central corneas are an independent risk factor forpostLASIK ectasia, said William B. Trattler, MD, director ofcornea at the Center for Excellence in Eye Care, Miami. Eyes witha thin cornea (less than 500 µm) and normal topography areat no greater risk than those with thicker corneas of developingpostoperative ectasia and may be biomechanically strong andsimilar to thicker corneas in their behavior, Dr. Trattleradded.

He drew these conclusions from a study of the characteristics ofectasia cases that he and colleagues had performed as well as aliterature search. This analysis revealed that the majority ofcases of postLASIK ectasia occurred in corneas with apreoperative thickness above 500 µm and that other riskfactors for ectasia typically were present preoperatively in eyeswith thinner corneas. Dr. Trattler suggested that a patient witha thin cornea and topographic abnormality such as forme frustekeratoconus (FFK), keratoconus, or pellucid, which means that thecornea is biomechanically weak, should be considered at high riskfor postLASIK ectasia.

He also observed that although African Americans have thinnercorneas than Caucasians on average, no peer-reviewed studies havefound that they are more likely to develop conditions such as FFKor keratoconus.

Dr. Trattler also recommended that clinicians use preoperativetopography in screening LASIK candidates and that further studiesbe conducted to help define which patients have an increased riskof developing ectasia.

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