The erodible mask in photorefractive keratectomy for myopia and astigmatism

This paper reports a new approach for performing photorefractive keratectomy (PRK) that uses an erodible mask to control shape transfer processes. The advantages of this technique, when compared to conventional PRK performed with mechanical diaphragm, are 1) the possibility of transferring almost any shape onto corneal surface; 2) a smoother corneal surface following photoablation; 3) easier eye fixation; and 4) a controlled humidified environment over ablation zone. We report our experimental study on scanning electron microscopy of polymethylmethacrylate (PMMA) plates ablated using conventional technique versus erodible mask technique; the results showed a smoother surface in the PMMA plate ablated using the erodible mask. We also report our preliminary clinical results of four eyes treated for the correction of myopia combined with astigmatism. Myopia ranged from -2.00 to -10.00 D, and astigmatism ranged from -1.50 to -2.50 D. Three months after surgery, all four eyes were within +/- 1.00 D of myopic attempted correction, but astigmatism was completely corrected only in one eye. No complications or scarring have been reported. We believe the erodible mask could be effective in the correction of myopia and myopic astigmatism, but further improvements are necessary to allow easier alignment of the mask over the eye. All commonly available excimer laser devices produce photorefractive keratectomy as a concentric ablation of the corneal stroma, deeper in the center than in the peripheral part; this is produced by means of an iris or diaphragm which, depending on the type of laser, progressively opens or closes, allowing a greater laser beam delivery in the center.(ABSTRACT TRUNCATED AT 250 WORDS)