Home > Encyclopedia of Nursing & Allied Health > Radial Keratotomy

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.

Aftercare

After surgery, some patients feel pain and are given eye drops and medications to relieve discomfort. For several days the eye may feel scratchy and look red. This is normal. The eye also may water, burn, and be sensitive to light.

Patients should be advised to use eye drops for several weeks to protect against infection. Patients also should be told to protect the head and eyes.

The cornea heals slowly, and full recovery can take months. This is one reason RK has fallen out of favor with surgeons and patients. Laser-refractive surgeries, such as laser-assisted in situ keratomileusis (LASIK), have better results with faster recovery. Such procedures as LASIK and corneal rings have rendered RK virtually obsolete.

While the cornea is healing, patients may experience better eyesight in the morning than in the evening (or vice versa); pain; glare; starburst or halo effects; or a hyperopic shift. As the cornea flattens, vision may become more hyperopic. For this reason, the surgeon may initially undercorrect the patient. This gradual shift may occur over several years. This procedure leaves permanent scars on the cornea.

If RK does not completely correct nearsightedness, corrective lenses may be needed. Presbyopic patients will still require reading glasses.

Patients return to the surgeon for a follow-up exam one day post-operatively. After that, patients may be referred to the co-managing optometrist for the subsequent three or four visits. Patients should be advised to report any pain or nausea immediately to the attending physician.

Complications

Complications from RK include:

• cataract
• infection
• lasting pain
• tears along an incision, especially after being hit in the head or eye
• vision loss
• hyperopic shift

Complications are reduced when an ophthalmologist experienced with RK performs the surgery. Younger patients also tend to heal faster.

Results

The desired result of radial keratotomy is myopia reduction. A study reported by the National Eye Institute in 1994 tracked the success of 374 patients who had RK 10 years earlier. The study found that:

• 85% had at least 20/40 vision
• 70% did not need corrective lenses for distance vision
• 53% had 20/20 vision without glasses
• 30% still needed glasses or contact lenses to see clearly
• 1-3% had worse vision than before they had RK
• 40% had a hyperopic shift

Health care team roles

Allied health professionals help prepare patients for refractive surgery. Advanced and intermediate level ophthalmic technicians perform refractions and help determine the patient's eligibility for surgery. These professionals also may perform corneal topography.

Specially trained ophthalmic nurses assist during surgery. They prepare the operating room and equipment, and administer eye drops. Advanced ophthalmic technologists, who are trained for such additional duties as taking ophthalmic photographs and using ultrasound, may administer eye medications, perform tests, maintain surgical equipment and assist in refractive surgery.

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KEY TERMS

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Cornea—The transparent part of the eye that covers the iris and the pupil.

Diopter (D)—Unit describing the amount of focusing power of a lens.

Iris—The colored part of the eye.

Laser-assisted in situ keratomileusis (LASIK)—A type of refractive eye surgery using a laser and microkeratone to change the shape of the cornea.

Local anesthetic—Used to numb an area in which surgery or another procedure is to be done, without causing the patient to lose consciousness.

Myopia—Nearsightedness. People with myopia cannot see distant objects clearly.

Ophthalmologist—A physician who specializes in treating eyes.

Photorefractive keratectomy (PRK)—A type of refractive eye surgery using a laser to change the shape of the cornea.

Pupil—The part of the eye that looks like a black circle in the center of the iris. It is actually an opening through which light passes.

Retina—A membrane lining the back of the eye onto which light is focused to form images.

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Training

The American Society of Cataract and Refractive Surgery keeps physicians informed of the latest advances in surgery. Optometrists are advised to observe surgeries and attend seminars to learn more about follow-up treatments.

Ophthalmic assistants who want to assist in these surgeries can receive additional training from certified education programs.

Mary Bekker