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Radial keratotomy was an early surgical treatment for myopia ("nearsightedness"), and the first formalized procedure to permanently improve eyesight. Expressed simply, much of the eye is a device for focusing light on the retina. Myopia is a common condition in which the focal point of light in the eye comes to be in front of the retina, due to excessive elongation of the eye or curvature of the cornea. Traditionally, this had been "treated" (or rather, compensated for) by placing a concave lens in front of the eye, in the form of contacts or glasses, but in theory it could also be corrected by compressing the eye or reducing corneal curvature. This latter possibility is where radial keratotomy comes in.

Radial keratotomy is the process of making microscopic radial slits in the surface of the cornea, which if placed correctly will cause the cornea to heal flatter, moving the focal point of light in the eye back towards the retina. Ophthalmologists use a somewhat complex set of equations to determine exactly where to cut in order to restore a given eye to 20/20 vision, and with the proper patterning and the incorporation of tangential incisions, it is also possible to treat astigmatism to some degree. The eye is functional two hours after the surgery, though irritable, with fluctuations in vision common initially, though tending to stabilize with time, although some follow-up reports indicate some degree of change continuing up to 10 years afterwards in some patients. Glare and "starburst" at night have also been reported, also tending to diminish with time. A small percentage of patients report infection or deterioration of vision, though overall, results are generally good, with the majority of patients reporting significant improvement, over half to 20/20 vision.

The development of radial keratotomy was another one of those "happy accidents" that characterize a disturbing proportion of human progress. In the Soviet Union of the 1970s, a young boy at play broke his glasses, and the glass shards cut into his eyes. (Modern children's glasses in the United States are made of plastic and polymers specifically to prevent such an eventuality.) It was observed, however, that when his eyes healed, his vision in fact improved. The eminent ophthalmologist (and later Russian Federation presidential candidate) Svyatoslav Fyodorov, who was treating the boy, took note of this, and drawing on the experience and the mostly overlooked work of Tsutomu Sato, developed the theory and practice of radial keratotomy, with some early tests so crude as to be performed by hand with a razor blade.

Thus refined, the practice spread to other countries in the 1980s, and worldwide surgeries during this period numbered in the millions. Eventually, however, the practice fell out of favor with the development of laser eye surgery methods such as photorefractive keratectomy (PRK) and Laser in-situ Keratomileusis (LASIK), which were more sterile, more precise, generally yielded better results and fewer complications, and could be used to treat a wider range of optical flaws. Radial keratotomy has mostly been abandoned in favor of these new methods, and the procedure is generally considered obsolete.

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