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S. Esquenazi, J. He, N. Li, K. Esquenazi, H. Bazan; Cellular Response of Rabbit Corneas Following Collagen Cross-Linking is Not Affected by Epithelial Removal. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5000.
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Corneal collagen cross-linking creates additional chemical bonds by means of a photopolimerization in the anterior stroma while minimizing exposure to the surrounding structures of the eye. This treatment is a new hope in the management of keratoconus and corneal ectasia after laser refractive surgery, corneal ulcers, stromal melting and collagenolisis and also to reduce corneal swelling in borderline endothelial function. However the epithelial defect produced has been associated with microbial keratitis, delayed wound healing and postoperative pain. The aim of the present study is to assess ultrastructural modifications in keratocyte population, myofibroblast generation and inflammatory cell response in rabbit corneas cross linked with and without epithelial removal.
Ten adult New Zealand albino rabbits weighing 2.0 to 3.0 kg were used in this study. Two rabbits served as controls. Four rabbits had their epithelium removed and four did not. All eyes were cross-linked with riboflavin 0.1% solution (10mgs riboflavin-5-phosphate in 10ml 20% dextran-T-500) applied every 3 minutes for 30 minutes, while exposed to UVA (360 nm, 3 mW/cm²) for 30 minutes. This corresponds to a total dose of 3.4 J or a total radiant exposure of 5.4 J/cm² to the cornea. Four rabbits were humanely euthanized at each time point: 3 days and 11days after the procedure. Tissue sections were evaluated with hematoxylin and eosin (H&E) stain and by immuno-histochemical analysis using specific antibodies.
A cytotoxic effect of combined riboflavin/UVA treatment was observed as early edema and keratocyte apoptosis and late compaction of anterior stroma fibers and displacement of cell nuclei in both groups. Eleven days after treatment H&E staining was observed in the treated area. Active keratocytes and alpha-SMA positive cells are present in the cornea below the treated area in both groups.
Our results suggest that there is no difference in the apoptosis response, inflammatory cell infiltration and appearance of alpha-SMA positive cells with or without epithelial removal. The presence of myofibroblasts in the area below the treated cornea may explain the mild cornea haze seen clinically in some patients after treatment.
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