Radial keratotomy

Patients who want to have good vision without the bother of eyeglasses, or who are contact-lens intolerant, have the option of undergoing radial keratotomy (RK) or other refractive procedures.

The Purpose of Radial Keratotomy
The aim of RK is to reduce myopia of between one and six diopters by reducing the curvature and thus the refractive power of the central optic zone of the cornea, the major refractive surface of the eye. This is accomplished by making a series of equally spaced radial incisions around the peripheral cornea, extending from the optical zone to the corneoscleral limbus (Figure 1). Additional slits can be added in subsequent operations if further reduction of curvature is required. The depth of the incision depends on the thickness of the cornea, which is measured by ultrasonography.

Figure 1.

The cuts are made through most of the corneal thickness with a diamond knife under microscopic observation. Subsequently, intraocular pressure pushes the peripheral cornea forward, flattening the central few millimeters of the cornea and reducing its curvature.
The length of the blade beyond its guide is preset to the desired depth of the incision. As the scalpel moves, it makes a uniform incision to approximately 95 percent of the cornea's thickness along the length of each incision.

Who is a Candidate for Radial Keratotomy?
Patients who are candidates for RK either have excess curvature of the cornea, elongated eyeballs, or both. Contraindications of RK include conditions that interfere with the surgery, such as severe dry eye, active corneal disease, uncontrolled glaucoma, retinal detachment, or cataract.
Preparations for RK may begin days or weeks before the actual procedure. Because contact lenses can mold to the cornea and change its curvature, patients who use hard lenses must remove them for three weeks before their preoperative examination. Patients who use soft lenses must remove them three days before the examination. The curvature of the cornea, uninfluenced by contact lenses, is then taken as a baseline. The preoperative workup is extensive and includes a topographical analysis of the cornea to ascertain its curvature and focal point using a computerized corneal mapping system.
After routine preparations in the OR are completed, the procedure itself takes about 10 to 15 minutes. It is performed on only one eye per visit. Recovery takes one to two days.

The Results of Radial Keratotomy
The addition of distance glasses can improve vision after surgery from 20/40 or greater to 20/20. When indicated, it is safe to use glasses for driving and other activities requiring sharp distance vision.
Despite the basic simplicity of the procedure and the high probability for success, RK is a surgical procedure, and as such, it carries with it potential complications. For example, the patient might temporarily experience glare when looking at bright objects, or they might experience fluctuating vision, which may be better in the morning than in the evening. This phenomenon results from the flattening of the cornea under the eyelids at night. While the surgery is intended to correct distance vision, near vision is usually not affected. However, reading glasses or bifocals may be needed at around age 40, which is earlier than with uncorrected myopia.

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