[In vivo evaluation of corneal structure changes after refractive procedures]

The aim of the study was to evaluate and compare in vivo the corneal structure changes after refractive procedures (PRK, LASIK, LASEK).

The analysed group of patients consisted of 226 corneas in 126 patients, who underwent correction of myopia and myopic astigmatism, using the procedures: PRK (120 eyes), LASIK (56 eyes) and LASEK (50 eyes). The photoablation of the corneas was performed with the Excimer Laser MEL 60 and MEL 70 G-Scan Aesculap Meditec. Postoperative observations were made using a confocal microscopes Confoscan P4 (Tomey) and ConoScan 2 (Fortune Technologies). The evaluations were performed in the early (up to 3 months) and late postoperative period (after PRK and LASIK-up to 2 years; after LASEK-up to 6 months).

The confocal microscopy revealed some changes within the corneal epithelium and anterior part of stroma after PRK, LASIK and LASEK. After PRK, there was increased desquamation of superficial epithelial cells in early postoperative period. These cells were elongated after LASIK and LASEK procedures. After PRK and LASEK, the Bowman's membrane was absent in the central part of the cornea, during the whole observation period. After all these procedures, the anterior part of the corneal stroma in the ablation zone, showed increased background illumination of collagen fibres and an irregular pattern of elongated keratocytic nuclei, in the early postoperative period. No scar tissue--"haze" was found in cases after LASEK, what may occur after PRK procedure. The findings kept changing in the course of the follow up time.

Confocal microscopy enables in vivo monitoring of changes, which occur in the corneal structure after refractive procedures; this facilitates the evaluation of corneal healing. LASEK is the least invasive refractive procedure, which allows prompt stabilization of the corneal structure.