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Background: Corneal barrier function following photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) was evaluated to determine corneal damage and to compare the amount of corneal trauma associated with haze development with the two procedures., Methods: The PRK and LASIK procedures were performed with the Nidek EC-5000 excimer laser. The Chiron Hansatome microkeratome was used in the LASIK procedures. We followed 1528 eyes of myopic patients (range, -1.00 to -23.00 D) classified into three groups according to age. Each group was divided into four subgroups depending on the amount of myopia (-1.00 to -2.75 D; -3.00 to -5.75 D; -6.00 to -9.75 D; -10.00 to -23.00 D). In eyes with haze formation, haze intensity and postoperative period of haze development were evaluated. The corneal uptake was 5.6 carbonfluorescein 5%, and a computer program analyzed video slit-lamp corneal images., Results: PRK and LASIK increased corneal permeability to fluorescein (2 to 8 weeks after PRK and 4 to 6 weeks after LASIK). Deeper ablations showed higher corneal fluorescein permeability for longer periods. In eyes with haze formation, an increased index of corneal fluorescein permeability was observed in the eyes with early postoperative haze formation (1 to 2 months) and a decreased index of corneal permeability was observed in eyes with late postoperative period haze formation (after 3 months). This finding suggests a difference in the haze that developed in the early and later postoperative periods. Fluorescein permeability after PRK returned to normal in 2 to 8 weeks and remained constant. Following LASIK, fluorescein permeability returned to normal in 4 to 6 weeks. Decreasing corneal permeability to fluorescein was observed 2 to 6 months after LASIK, and returned to normal at 6 months., Conclusion: Photorefractive surgery disrupts corneal barrier function for up to 6 months postoperatively, even though other clinical tests of the cornea may be normal. This finding may help explain some mechanisms of pathogenesis of complication development following PRK and LASIK. The fluorescein permeability findings demonstrated different mechanisms for early and late haze formation after PRK.

Video images of the cornea in photorefraction keratectomy (PFK) are analyzed by computer-aided microdensitometric analysis of televideo images of the eye. Optic density of various layers of the cornea and fluorescein penetration through the cornea were assessed in patients with myopia (235 eyes) and hypermetropia (65 eyes) before the after PFK. PFK was carried out by Nidek excimer laser (Japan). Analysis was carried out with consideration for the degree of emmetropia and patients' ages. Corneal transparency and index of fluorescein penetration through the cornea correlated with patient's age and emmetropia. Computer-aided microdensitometric analysis of televideo images of the eye earlier detects changes in the cornea than routine methods. The authors discuss the probability of assessing corneal transparency for selection of patients for PFK.

Purpose: To introduce an image analysis of the cornea in photorefractive keratectomy (PRK) for preoperative and early postoperative determination of changes in the condition of the cornea., Methods: Slit-lamp videography was used to evaluate the cornea. Microdensitometry of the corneal images was performed. The optic density of the anterior, middle, and posterior corneal layers was measured. Photorefractive keratectomy was performed with the Nidek EC-5000 excimer laser. We followed patients with different amounts of myopia (range, -1.00 to -20.00 D) classified into three groups, according to age. Each age group was divided into four subgroups depending on the amount of myopia., Results: The analysis of the microdensitometry results of the optic section of transparent corneas in myopic patients demonstrated differences depending on age and mean amount of myopia. A correlation between the microdensitometric data of permeability by fluorescein and the refractive results of PRK was found., Conclusion: Quantitative image analysis of the cornea is a useful method to evaluate the condition of the cornea before and after PRK. This method can identify early damage to the cornea in myopia patients. Preoperative investigation of permeability of the cornea using fluorescein is an important method for selection of the patients for PRK.