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Histological Examination on Rabbit Corneas following Photo-refractive Keratectomy (PRK)

1Resch M., 1Szentmáry N., 1Nagy Z. Z., 2Szende B., 1Süveges I.,
1Medical University Semmelweis, 1st Department of Ophthalmology (Budapest)
2Semmelweis Egyetem, I. sz. Kórbonctani és Kísérleti Rákkutató Intézet (Budapest)

Purpose: The transparency of the cornea is temporary decreased after excimer laser treatment because of the stromal disregulation and remodelling of the collagen fibers and the extracellular matrix (ECM) components.
Methods: Photorefractive keratectomy (PRK) was performed on the right eyes of 17 pigmented rabbits with an Asclepion Meditec MEL 70 G-scan excimer laser. After manual epithelium removal with a 6.0 mm ablation zone 82 micron deep photoablation was carried out. No postoperative medication was used. The left untreated eyes served as controls. 5 groups were created: 1 day, 4 days, 1, 2 and 4 weeks after treatment the enucleated eyes were macroscopically examined and the cornea was fixed and stained with hematoxylin-eosin (HE), Periodic-acid Schiff (PAS), trichrome, alcian-blue and Ag-impregnation for histological investigation.
Results: According to the fotoablation zone haze was observed in all treated eyes from 1 day to 4 weeks postoperatively. In the field of haze with HE staining compared to the control eyes in days 1 and 4 loss of keratocytes, 1,2 and 4 weeks increased keratocyte density was seen. In the anterior stroma PAS and trichrom stain showed abnormal lamellae with fibrillar appearance after 2 weeks. Alcian-blue stained the sulfated glycosaminoglycans (GAG) from day 4 increasing to 4 weeks. Ag-impregnation marked the subepithelial basal laminae.
Conclusions: PRK induces in early stages loss of keratocytes, destruction of collagen fibrils and ECM. Later, during regeneration more keratocytes appear in the anterior stroma and the newly synthesised collagen and GAG molecules are disorganised and have cicatrical characteristics.