Results of the prospective evaluation of radial keratotomy (PERK) study 10 years after surgery
G. O. Waring 3rd, M. J. Lynn and P. J. McDonnell
Prospective Evaluation of Radial Keratotomy Coordinating Centers, Emory University, Atlanta, Ga.
OBJECTIVE: To determine the long-term effects and stability of refraction
following a standardized technique of radial keratotomy for myopia in the
nine-center Prospective Evaluation of Radial Keratotomy (PERK) Study 10
years after surgery. METHODS: Radial keratotomy using eight centripetal
incisions was performed to reduce myopia of -2.00 to -8.75 diopters in 1982
and 1983. A mean of 10 years later, patients underwent a standardized
ophthalmic examination similar to previous study examinations. RESULTS: Of
427 patients (793 eyes that underwent radial keratotomy), 374 patients
(88%) (693 eyes) returned for the 10-year examination. Of 675 eyes with
refractive data, 38% had a refractive error within 0.50 D and 60% within
1.00 D. For 310 first-operated eyes, the mean refractive error was -0.36 D
at 6 months and changed in a hyperopic direction to + 0.51 D at 10 years.
The average rate of change was +0.21 D/y between 6 months and 2 years and
+0.06 D/y between 2 and 10 years. Between 6 months and 10 years, the
refractive error of 43% of eyes changed in the hyperopic direction by 1.00
D or more. The hyperopic shift was statistically associated with the
diameter of the clear zone. Uncorrected visual acuity was 20/20 or better
in 53% of 681 eyes and 20/40 or better in 85%. Loss of spectacle-corrected
visual acuity of 2 lines or more on a Snellen chart occurred in 3% of all
793 eyes that underwent surgery. Among 310 patients with bilateral radial
keratotomy, 70% reported not wearing spectacles or contact lenses for
distance vision at 10 years. CONCLUSION: The PERK technique of radial
keratotomy eliminated distance optical correction in 70% of patients, with
a reasonable level of safety. A shift of the refractive error in the
hyperopic direction continued during the entire 10 years after surgery.
