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Photorefractive keratectomy for residual myopia after radial keratotomy. PRK After RK Study Group
1Corneal and Refractive Surgery Services, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts 02114, USA.
Purpose:
To evaluate the visual outcomes in patients having photorefractive keratectomy (PRK) to correct residual myopia after radial keratotomy (RK).
Setting:
Nine refractive surgery centers in the United States and one in South Korea.
Methods:
This retrospective analysis comprised 38 eyes of 32 patients treated with PRK after RK and followed for 12 months. Analysis was based on pre-RK and pre-PRK refraction as well as response to RK (pre-RK minus pre-PRK refractions).
Results:
Mean pre-RK and pre-PRK refractions were -8.11 diopters (D) +/- 2.92 (SD) and -4.28 +/- 2.08 D, respectively. One month after PRK, mean refraction was +0.42 +/- 1.56 D and regressed to -0.95 +/- 1.24 D at 12 months. At 12 months, 65% of eyes had an uncorrected visual acuity of 20/40 or worse, and 11.1% lost 2 or more lines of best corrected acuity. Of eyes with an original erro of -6.00 or less, 81.8% were within +/- 1.00 D of intended correction at 12 months and of those with an original error of -9.12 to -20.00 D 50.0% (P = .004). All eyes with residual (pre-PRK) errors of -3.00 D or less and 42.9% with a residual error of -6.12 to -9.00 D were within +/- 1.00 D of intended correction (P = .07). There were no statistically significant differences in the response to PRK between eyes that had an RK response of 0 to 3.00, 3.12 to 6.00, or 6.12 to 12.00 D.
Conclusion:
Patients with lower original and residual myopia achieved better visual outcomes after PRK than those with higher myopia. The amount of myopic correction achieved using RK was not predictive of the amount of myopic correction using PRK.