Radial Keratotomy Health Article

Definition

Radial keratotomy (RK) is eye surgery performed to correct myopia by changing the cornea's shape.

Purpose

RK was introduced in North America in 1978. RK is one of several surgical techniques for reducing or eliminating the need for corrective lenses. It is most successful in patients with low to moderate nearsightedness—people whose eyes require up to -5.00 diopters of correction.

Precautions

RK cannot help patients whose nearsightedness is caused by keratoconus, a condition in which the cornea is cone-shaped. The procedure usually is not performed on patients under 18 because their vision is unstable. Women who are pregnant, have just given birth, or are breast-feeding should not have RK because hormones may cause temporary corneal changes. Glaucoma patients or patients with any disease that interferes with healing should not have RK.

Radial keratotomy weakens the cornea, making it vulnerable to injuries long after surgery. A head injury after RK can cause the cornea to tear and can lead to blindness. Sports enthusiasts should be warned of this danger.

RK's success cannot be guaranteed. An ophthalmologist estimates the probability of the surgery's success in correcting vision. In some cases, patients with myopia that has caused their near vision to be clear prior to surgery may need corrective lenses for near vision following surgery. Some patients still require lenses for distance vision. RK does not eliminate presbyopia and the eventual need for reading glasses.

Description

With clear vision, light passes through the cornea and the lens of the eye and focuses on the retina. In a myopic patient, the eyeball is usually too long, so that light focuses in front of the retina. RK reduces myopia by flattening the cornea. This flattening reduces the cornea's focusing power, allowing the light to focus further back onto the retina, forming a clearer image.

For RK, a surgeon uses a small diamond-blade knife to make four to eight radial incisions approaching the edge of the cornea. These slits are made in a pattern that resembles the spokes of wheel. As the cornea heals, its center flattens.

Before surgery the patient is given a sedative. A local anesthetic—usually eye drops—is used to numb the eye. The patient remains conscious during the procedure. The surgeon utilizes a surgical microscope to magnify the cornea while making the slits. The treatment usually lasts 30 minutes.

Most ophthalmologists perform RK on one eye at a time. Surgeons once thought they could use the results of the first eye to predict how the well the procedure would work on the second eye. However, a study in the American Journal of Ophthalmology in 1997 found that this was not the case. The authors cautioned that there might be other reasons not to operate on both eyes at once, such as increased risk of infection.

RK's costs depends on the surgeon, but usually range from $1,000 to $1,500 per eye. It is usually not covered by insurance.

Preparation

RK patients should be carefully screened by an ophthalmic assistant or physician before surgery is approved to avoid possible complications. This screening should include a comprehensive eye exam, either by the ophthalmologist, or a co-managing optometrist at least a few days before surgery. At this time, the physician or ophthalmic

assistant should chart any dry eye or any corneal disease that may hinder surgery. They also should perform corneal topography, which creates a map of the patient's eye.

Assistants must advise patients to discontinue wearing contact lenses weeks prior to the visual exams to make sure vision is stable; and they must also advise the doctor of contact lens wear.

Before surgery, ophthalmic staff administer eye drops and a sedative to the patient. The physician tests the patient's vision, and the patient rests while waiting for the sedative to take effect. Immediately before the surgery, ophthalmic staff administer local anesthetic eye drops.

Before beginning the procedure, the surgeon measures the cornea's thickness to decide how deep the slits should be, and marks an area in the center of the cornea called the optical zone. This is the part of the cornea in the area over the pupil that the patient sees through. No cuts are made in this region.