Corneal Epithelial and Stromal Reactions to Excimer Laser Photorefractive Keratectomy: III. The Excimer Laser and Radial Keratotomy: Two Vastly Different Approaches for Myopia Correction

Excimer laser photoablation was first used clinically in ophthalmology to make semiradial and linear transverse excisions^1-3 in an attempt to improve traditional diamond-knife radial keratotomy (RK). Traditional diamond-knife RK, which is currently limited to correcting the visual acuity in eyes with less than 7.00 to 8.00 diopters (D) of myopia, depends on corneal wound healing to achieve the final result.² Compared with diamond-knife incisions, excimer laser excisions create wider wounds because tissue is removed,⁴ provide less control over wound depth, and increase the likelihood of endothelial cell rupture.⁵ Consequently, attention was directed toward wide-area lamellar stromal excision, so-called photorefractive keratectomy (PRK), in an attempt to achieve safe and more predictable corneal flattening and myopia reduction.⁶ The results of such studies and others^7-10 in human eyes, together with the report in this issue,¹¹ provide preliminary information on the efficacy, predictability, and safety of the procedure.