Excimer laser corneal surgery: new strategies and old enemies.

Although refractive errors are extremely common, their pathogenesis remains undetermined; both genetic and nongenetic factors appear to influence an individual's risk for myopia and the severity of the myopia. The pursuit of good visual acuity without corrective spectacles or contact lenses has spawned a large number of surgical procedures designed to correct myopia, hyperopia, and astigmatism, with the first published descriptions of corneal incisions for this purpose appearing 100 years ago. Two thirds of the refractive power of the eye resides within the cornea, so most of these procedures involve surgical manipulation of the cornea (keratorefractive surgery). Exciting new technologies are being developed for use in refractive surgery, but variability in wound healing remains an old enemy. Predictability of keratorefractive surgery would be greatly improved by a better understanding of corneal biomechanics and by effective strategies for pharmacologic manipulation of wound healing within the cornea. The global public health and socioeconomic implications of safe, effective, and predictable refractive surgery are enormous; about one fourth of the United States population has myopia, and in other regions of the world the prevalence of myopia may reach 70%.' If a cost-effective surgical procedure were developed, the avoidance of decades of contact lens or spectacle wear could save billions of dollars.