Purpose: To assess the response of the cornea to hydrogel intracorneal lens (ICL) insertion or laser in situ keratomileusis (LASIK) with IntraLase (IntraLase Corp.) at the cellular level. Setting: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA. Methods: Twenty patients (29 eyes) were evaluated by in vivo confocal microscopy 1 to 6 months postoperatively: 20 eyes had LASIK with flap creation by IntraLase, and 9 eyes had ICL insertion (8 following IntraLase). Results: For LASIK with IntraLase, keratocyte activation and/or interface haze was detected in 8 of 20 eyes. The remaining eyes had interface particles but no cell activation. Keratocyte activation was generally limited to a few cell layers adjacent to the interface. However, 2 patients exhibited multiple layers of activation and increased extracellular matrix (ECM) reflectivity (haze) surrounding the interface by confocal microscopy. Both patients also had clinical haze and photophobia. For ICLs, following insertion, 5 of 9 eyes had activated keratocytes adjacent to the implant surfaces. The largest amount of cell activation and ECM haze detected by confocal microscopy was in 2 patients with significant clinical haze. Structures with an epithelioid morphology were detected on some implant surfaces. Epithelial thickness was 33.3 μm ± 2.3 (SD) in the ICL eyes and 49.2 ± 6.5 μm in the LASIK with IntraLase eyes. Conclusions: Both LASIK with IntraLase and ICL insertion following IntraLase induced keratocyte activation, which may underlie clinical observations of haze in some patients. Intracorneal lens implant also induced thinning of the overlying corneal epithelium.
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