Keratocyte Response Following INTACS®, Intracorneal Lens Inserts, and Flap Creation by Femtosecond Laser Ablation (Intralase®) for LASIK

Abstract

Abstract: : Purpose: Several different surgical techniques have emerged in recent years which rely on either mechanical stress (e.g INTACS), tissue removal (e.g. LASIK) or tissue addition (e.g. intracorneal lens inserts) to correct refractive errors. The purpose of this study was to compare the corneal response to these insults using in vivo confocal microscopy. Methods: A total of 14 patients (17 eyes) were evaluated: 5 eyes that had undegone LASIK with flap creation by Intralase® (3–4 months post–op), 7 eyes with intracorneal lens inserts (PermaVision®, 1–6 months post–op), and 5 patients with INTACS® (5 years post–op). Tandem scanning confocal microscopy (TSCM) was used to measure epithelial thickness, and identify morphologic changes in the corneal stroma following these procedures. Results: TSCM identified keratocyte activation and deposition of extracellular matrix (fibrosis) in two of five eyes that had undergone LASIK with Intralase®; the other three eyes had interface particles but no cell activation or detectible ECM deposition. Interestingly, the patient with the largest amount of fibrosis (40 *m thick) also exhibited delayed light sensitivity syndrome clinically. Following intracorneal lens insertion, 4 of 7 eyes had keratocyte activation and fibrosis adjacent to both the anterior and posterior surface of the implant. Interestingly, epithelial thickness was reduced in these patients as compared to the Intralase® patients (34.8 + 6.4 *m vs. 45.2 + 6.4 *m, p < 0.05). Following long–term use of INTACS, abnormal ECM deposition (haze) was observed in varying degrees in all five patients adjacent to the implant. Interestingly, bright, crystal–like structures consistent with lipid deposition were also observed in three patients. Conclusions: Both Intralase® and intracorneal lens insertion can induce keratocyte activation and ECM deposition in some patients; in general this response is greater than that previously observed following traditional LASIK, consistent with clinical observations of haze and/or delayed light sensitivity in some cases. In addition to ECM deposition, long–term mechanical perturbation following INTACS appears to result in lipid synthesis by corneal keratocytes in a subset of patients.

Keywords: cornea: clinical science • cornea: stroma and keratocytes • refractive surgery: comparative studies