Results of the Prospective Evaluation of Radial Keratotomy (PERK) study four years after surgery for myopia

Article Abstract:

Myopia, or nearsightedness, affects about 25 percent of adults in western countries. In myopia, incoming rays of light are excessively refracted so that they focus in front of the retina, rather than reaching the retina at their focal point; this causes blurred vision. Eyeglasses and contact lenses are used to correct the refractive error and project images onto the retina properly. In order to do without corrective lenses, many patients have undergone a new surgical procedure called radial keratotomy; hundreds of thousands have had the surgery worldwide during the past decade. Incisions are made in the cornea, the surface of the eyeball, and the result may be a permanent correction of myopia. But the safety and effectiveness of this procedure is still controversial. The condition of 400 patients four years after radial keratotomy is reported. The study, called the Prospective Evaluation of Radial Keratotomy (PERK), was conducted at nine different clinical centers where the surgery was performed with diamond-bladed knives rather than the metal blades used in some other trials. Subjects had the procedure on only one eye at a time. Results showed that vision was 20/40 or better in 76 percent of the eyes that had the procedure. Fifty-five percent of eyes had a refractive error of less than 1.00 diopter (D). While 28 percent were undercorrected (still nearsighted), 17 percent were overcorrected so that the eye was now farsighted. The degree of correction was considered unpredictable. Also, refractive error continued to change by more than 1.00 D in 23 percent of the eyes between six months and four years after surgery. Of the 323 patients who had the procedure on both eyes, 64 percent wore no corrective lenses. Complications which were not considered severe included bacterial infections, difficulty with night driving due to glare from headlights, and the inability to correct vision perfectly without corrective lenses. Severe complications have rarely occurred in other studies and did not occur in the PERK study. To be eligible for the radial keratotomy a patient must have myopia of moderate degree, meaning correction of -2.00 to -6.00 diopters. (Consumer Summary produced by Reliance Medical Information, Inc.)

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Radial keratotomy in the 1990s and the PERK study

Article Abstract:

In myopia, or nearsightedness, rays of light entering the eye are excessively refracted and do not reach the retina at the back of the eye; this causes blurred vision. Many people wear eyeglasses or contact lenses to correct this refractive error (by projecting images onto the retina). But in the hope of giving up their corrective lenses, many patients have undergone a new surgical procedure called radial keratotomy. Incisions are made in the cornea, the surface of the eyeball, in an attempt to permanently correct the myopia. In the February 23, 1990 issue of The Journal of the American Medical Association, an article by G.O. Waring, III and colleagues discusses a follow-up of patients who had the procedure four years earlier; the study was called the Prospective Evaluation of Radial Keratotomy or PERK. Some patients had the surgery on one eye only, while others had both eyes treated; follow-up examinations of 390 eyes were reported. While radial keratotomy was once considered to be a risky procedure of unproven effectiveness, the technique has improved and the results of the PERK study are very good. Some eyes (28 percent) were undercorrected (still myopic) after surgery, but this was not a serious complication because vision had still been improved. A more undesirable consequence was the overcorrection of 17 percent of the eyes, which rendered them farsighted; this is the most common and unfortunate complication of the surgery. Two-thirds of the patients were able to stop wearing eyeglasses or contact lenses; others were using one hard contact lens to correct for the imperfect results of surgery. While radial keratotomy is not a foolproof procedure, it should become more effective as the techniques and surgical skills are refined. (Consumer Summary produced by Reliance Medical Information, Inc.)

editorial

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Radial keratotomy: this surgery involves more than meets the eye

Article Abstract:

More and more nearsighted Americans are turning to radial keratotomy, a surgical procedure to change the cornea's shape, to avoid the use of eyeglasses and corrective lenses. A recent study by the National Eye Institute shows that radial keratotomy was effective in 70% of patients.

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