The apoptosis and proliferation after photorefractive keratectomy

Objective: To search the correlation between the apoptosis and proliferation of keratocytes and investigate the influence of phototherapeutic keratectomy (PTK) and mechanical epithelial scrape (MES) on keratocyte apoptosis and proliferation.

Methods: Rabbit corneas received photorefractive keratectomy (PRK, -9.9 diopters, 6 mm diameter). Animals were evaluated subsequently up to 6 months after surgery by in vivo confocal microscopy. Corneas were prepared for H.E. staining, corneal cell apoptosis was evaluated by terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) to detect DNA fragmentation.

Results: Loss of keratocytes and keratocyte death were found anteriorly in the remaining stroma at 4h after PRK. Activated keratocytes observed by confocal microscopy repopulated within 1 month. A significant elevation of apoptosis was detected in keratocytes and epithelium at 4h, 3d, 1m after PRK. The level of keratocyte apoptosis was parallel to the loss of keratocytes at the early stage and was correlated with keratocyte proliferation in the later stage, PTK-PRK was associated with lower levels of central corneal apoptosis and activated keratocytes than MES-PRK.

Conclusions: It is suggested that the loss of keratocytes and keratocyte apoptosis be correlated with keratocyte activation and proliferation, which may result in haze and regression after PRK, and PTK-PRK induce lower level of early keratocyte apoptosis and late keratocyte activation than MES-PRK.