Corneal transparency and measurement of corneal permeability in excimer laser photorefractive keratectomy

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 myopic patients. Preoperative investigation of permeability of the cornea using fluorescein is an important method for selection of the patients for PRK.