| Wound healing is critical to all corneal surgical procedures. Corneal wound healing also contributes to the efficacy and safety of refractive surgical procedures such as photorefractive keratectomy (PRK) and laser in situ keratomeliusis (LASIK), since it is a major factor in over-correction, under-correction, stromal opacity, and other complications that ethier myopia or hyperopia.In last decade, many ophthalmologists have paid attention to the wound healing response to the corneal refractive surgery. It was first demonstrated in 1996 that the early disappearance of keratocytes that follows epithelial injury is mediated by apoptosis.Apoptosis is a programmed cell death and plays a majorrole in modulating many physiological and pathological processes and apoptosis is gentle involutional form cell death that occurs without the release of lysosomal enzymes or other intracellular components that cound damage the surrounding tissues or cells. Subsequent studies have suggested that apoptosis is mediated by cytokines such as IL-1, Fas-L, BMP-2, BMP-4, TNF-a released from the injured epithelium and the maditude of keratocyte apoptosis at 4 hr time point paralleled the level of keratocyte proliferation and myofibroblast density in stroma.The keratocyte apoptosis response is most commonly detected with the terminal-deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay and electron microscopy. Keratocyte apoptosis is detected within minutes of epithelial injury by electron microscopy. Conversely DNA fragmentation detected by the TUNEL assay takes longer to develop (10-30min) and has been found to be most prominent at approximately 4hr after scrape injury in mice and rabbits~[8,9]. Keratocyte apoptosis is the first observable stromal change following epithelial injury. Following initiation of keratocyte apoptosis,other cellular processes occur in stroma. Remaining keratocytes begin to proliferate and myofibroblasts may be generated~[10,11]. The complex cellular response contributes to stromal remodeling and modulated healing of the overlying epithelial cells.At present, laser in situ keratomeleusis (LAS1K) has become the most popular surgical technique for correcting refractive error, whereas the effect of LASIK is influenced with some factors, the most important factor is corneal wound healing.The present study included 20 rabbits that had LASIK (low or high ablation) for myopia or flap production only with qualitative and quantitative study of apoptosis, Transmission electron microscopy (TEM) was performed to confirm apoptosis. Through these methods to investigate the character of the keratocyte apoptosis after LASIK and to discuss the correlation between the level of apoptosis and the mechanical injury by micro- keratomy, laser ablationrespectively.[Objective]The aim of this study was to investigate the character of the keratocyteapoptosis after LASIK and to discuss the correlation between the level ofapoptosis and the mechanical injury by micro- keratomy, laser ablation respectively.[Methods]A total of 20 12- to 15- week-old New Zealand white rabbits weighting 3.5~4.0Kg each were included in the data analysis in this study.The 40 eyes were devided into 4 groups. Ten of these rabbits were operated with LASIK and were corrected -4.0 diopters on left eyes and -8.0 diopters on right eyes. The left eyes of the other ten rabbits were producted a flap with microkeratome without subsequent laser ablation and the right eyes were as control without any treatment.Anesthesia was obtained by intravenous injection of Pentobarbital Sodium (30mg/Kg) . In addition ,topical Oxybuprocaine 0.4% was applied to each eye just before surgery. After the animal under general and local anesthesia, the animal was laid on the operating-table. The microkeratome (Moria M2 ,France)was set to cut a flap 8.5mm in diameter and 130 μrn in thickness. After the production of flap ,a smooth round spatula was inserted into stromal interface and the flap was reflected on its hinge against the conjunctiva to expose the bed. Ac... |
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