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S.H. Chang, D. Tirrell, P. Nowatzki, D. Schwartz, R. Grubbs; Novel Corneal Implant Materials . Invest. Ophthalmol. Vis. Sci. 2006;47(13):64.
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The purpose is to develop a novel corneal onlay (implantable contact lens) material comprised of a genetically engineered artificial protein for reversible correction of refractive errors without removing corneal tissue.
The onlay material is prepared by standard methods of cloning, bacterial growth, and protein expression to produce the artificial protein. The artificial protein contains both cell attachment domains from elastin and mechanical structure domains from fibronectin to promote epithelial attachment and provide mechanical stability. The onlay is then molded from the crosslinked artificial protein.
Three groups of rabbits were used to study the biocompatibility and re–epithelialization of the artificial corneal onlay. Surgical wounds were created in Group 1 (n=5) without implant. Protein onlays were placed on the cornea surface without suture in Group 2 (n=12) and with suture in Group 3 (n=3). Fluorescein staining with blue light was used to assess the rate and extent of epithelialization. After 1 week, the animals were euthanized and the operated eyes were processed for histological examination.
In all cases epithelialization was initiated at the periphery of the corneal onlays and progressed inward toward the center. The control eyes (Group 1) showed commencement of epithelialization by Day 1 and full epithelialization within 2–4 days. All of the onlay eyes (Groups 2 and 3) showed epithelial cells on the onlay by Day 2 and full epithelialization within 4–7 days. Histological examination revealed that the corneal stroma posterior to the onlay and the corneal endothelium both appeared normal.
In preliminary studies, corneal epithelial cell proliferation and migration over and attaching to the implanted protein onlays were demonstrated in the rabbit model within 7 days. The genetically engineered protein onlays were fairly well tolerated by the rabbit eye.
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