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G.A. Peyman, C.F. Beyer, Y. Bezerra, J.M. Vincent, A. Arosemena, M.H. Friedlander; Photoablative Inlay Laser–Assisted in–Situ Keratophakia (PAI–LASIK) in the Rabbit Model . Invest. Ophthalmol. Vis. Sci. 2004;45(13):196.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the biocompatability and efficacy of a novel proprietary hydrogel photoablative inlay (PAI) which can be placed on the corneal stromal bed during laser in situ keratomileusis (LASIK), ablated with the excimer laser, and left to reside in the corneal stroma after flap replacement (PAI–LASIK). Methods: Several materials of various compositions were tested for suitability, measuring depth of ablation per pulse, microscopic profile after ablation, oxygen transmission, light transmission, and cytotoxicity. The chosen hydrogel material was evaluated for in vitro biocompatability using confluent monolayers of L–929 mouse fibroblast cells. The hydrogel material and a positive control were placed on the cell monolayers and incubated at 37oC in 5% carbon dioxide for 24 hours. The cell culture was examined macroscopically and microscopically to verify any cell lysis or toxicity. Eight New Zealand rabbits (1 eye each) underwent the PAI–LASIK procedure. Four eyes received a donut–shaped inlay; 4 eyes received a disc–shaped inlay. Each disc was first ablated with a programmed correction of 5 diopters of myopia. A corneal flap was created with a microkeratome employing a 160–µm head; the inlay was placed and centered on the corneal stromal bed and the flap replaced. The eyes were examined postoperatively and followed. The rabbits were sacrificed at 1, 4, 7, 11, or 16 months; the eyes were removed and prepared for light microscopy to evaluate the PAI and the cornea. Results: The chosen hydrogel material displayed no evidence of fracture, chatter, or cracking post excimer laser ablation, also retaining its clarity and contour. Cytotoxicity testing in vitro revealed no evidence of lysis when tested on fibroblast cells, suggesting no likelihood of cytotoxicity in vivo. The rabbit eyes showed no signs of rejection or extrusion of the implanted PAI after the LASIK procedure. The eyes receiving donut–shaped PAIs showed no difference in corneal clarity or healing rate compared with those with the disc–shaped inlays. One eye with a donut–shaped inlay had minimal corneal haze; the remaining inlays did not become opacified or fracture while implanted. Conclusions: A novel hydrogel material which is biocompatible and predictably ablatable by excimer laser can be used in the newly proposed PAI–LASIK procedure.
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