Radial keratotomy (RK) is a refractive surgical procedure to correct myopia (nearsightedness). It was developed in 1974 by Svyatoslav Fyodorov, a Russian ophthalmologist. It has been largely supplanted by newer, more accurate operations, such as photorefractive keratectomy, LASIK, Epi-LASIK and the phakic intraocular lens.
When performing RK, incisions are made with a diamond knife. The incisions relax the steep central cornea in patients with myopia in order to achieve a decreased need for correction. The original technique – consisting of incisions from periphery to center – was called the "Russian technique", while the later advances of performing controlled incision from center to periphery was called the "American technique".
RK may be performed with different types, numbers, and patterns of incisions. Typically, between 4 and 24 radial incisions are made in a number of patterns and orientations based on refractive errors, surgeon style and surgeon training. RK with 8 incisions is most common.
Incisions that penetrate only the superficial corneal stroma are less effective than those reaching deep into the cornea, and consequently, incisions are made quite deep. One study cites incisions made to a depth equivalent to the thinnest of four corneal-thickness measurements made near the center of the cornea. Other sources cite surgeries leaving 20 to 50 micrometres of corneal tissue unincised (roughly equivalent to 90% of corneal depth, based on thickness norms).
The procedure results in a decrease in nearsightedness. According to the PERK study, 58% of eyes were corrected within 1.00D of goal 3 years after surgery. Additionally, 76% of eyes had uncorrected vision of 20/40 or better at 3 years. From 2 to 10 years post-operatively 43% of eyes had an increase in farsightedness by 1.00D or more. Despite this, 70% of patients reported not requiring corrective lenses for distance vision 10 years after surgery.
The healing corneal wounds consist of newly abutting corneal stroma, fibroblastic cells, and irregular fibrous connective tissue.
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Refractive surgery is optional eye surgery used to improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This can include various methods of surgical remodeling of the cornea (keratomileusis), lens implantation or lens replacement. The most common methods today use excimer lasers to reshape the curvature of the cornea. Refractive eye surgeries are used to treat common vision disorders such as myopia, hyperopia, presbyopia and astigmatism.
An Intraocular lens (IOL) is a lens implanted in the eye usually as part of a treatment for cataracts or for correcting other vision problems such as short sightedness and long sightedness, a form of refractive surgery. If the natural lens is left in the eye, the IOL is known as phakic, otherwise it is a pseudophakic lens (or false lens). Both kinds of IOLs are designed to provide the same light-focusing function as the natural crystalline lens. This can be an alternative to LASIK, but LASIK is not an alternative to an IOL for treatment of cataracts.
Photorefractive keratectomy (PRK) and laser-assisted sub-epithelial keratectomy (or laser epithelial keratomileusis) (LASEK) are laser eye surgery procedures intended to correct a person's vision, reducing dependency on glasses or contact lenses. LASEK and PRK permanently change the shape of the anterior central cornea using an excimer laser to ablate (remove by vaporization) a small amount of tissue from the corneal stroma at the front of the eye, just under the corneal epithelium.
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