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Biomechanical failure may spur corneal ectasia after LASIK, PRK
Ophthalmology. 2008;115(12):2181-2191.
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A two-stage cascade of biomechanical breakdown contributes to corneal ectasia after LASIK and PRK, and mimics the failure process associated with keratoconus.
Ectasia after LASIK and PRK was linked with intralamellar and interfibrillar biomechanical slippage.
"This chronic biomechanical failure process is similar to that of intralamellar and interfibrillar slippage described with keratoconus," the study authors said.
The study included 13 corneal specimens from 12 patients undergoing penetrating keratoplasty for ectasia after LASIK (12 specimens) or PRK (one specimen). The specimens underwent light microscopy, transmission electron microscopy and immunofluorescence.
Light microscopy showed central epithelial hypoplasia or hyperplasia, small breaks in the Bowman's layer and thinning of the stromal bed in the ecstatic area of the cornea.
Further study is needed to determine whether new therapies such as corneal collagen cross-linking with riboflavin and ultraviolet A light may be used to treat corneal ectasia, the authors said.
This study examines the phenomenon of ectasia after corneal refractive surgery in previously normal eyes. Looking at histopathology, the study reports interlamellar slippage phenomenon to explain the onset of ectasia. In the long run, this may help us better understand the biomechanics of the cornea; why are some structures stable and others not? In concluding, the authors speculate that a “test” yet to be developed might help identify corneas pre-disposed to interlamellar slippage. Unfortunately, there is no immediate impact on clinical practice; the challenge of identifying unexpected “at risk” corneas remains.
– Roger F. Steinert, MD
OSN Cornea/External Disease Board Member