Three-year Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study

George O. Waring, Michael J. Lynn, William Culbertson, Peter R. Laibson, Richard D. Lindstrom, Marguerite B. McDonald, William D. Myers, Stephen A. Obstbaum, J. James Rowsey, David J. Schanzlin, Marguerite McDonald, Herbert E. Kaufman, Bruce A. Barron, Richard L. Lindstrom, Donald J. Doughman, J. Daniel Nelson, Penny Asbell, Hal D. Balyeat, Ronald E. Smith, James J. SalzRobert C. Arends, John W. Cowden, Robert L. Stephenson, Paul Fecko, Jerry Roust, Juan J. Arentsen, Michael A. Naidoff, Elisabeth Cohen, Jay H. Krachmer, Ceretha S. Cartwright, Robert J. Hardy, James P. McCulley, Robert D. Sperduto, Walter J. Stark, Richard A. Thoft, James V. Aquavella, Jules L. Baum, Joel Sugar, James Ware, George O. Waring

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


The Prospective Evaluation of Radial Keratotomy (PERK) study is a nine-center clinical trial of a standardized technique of radial keratotomy in 435 patients who had simple myopia with a preoperative refractive error between −2.00 and −8.00 diopters (D). The authors report results for one eye of each patient. The surgical technique consisted of eight incisions using a diamond micrometer knife with the blade length determined by intraoperative ultrasonic pachymetry and the diameter of the central clear zone determined by the preoperative refractive error. At 3 years after surgery, 58% of eyes had refractive error within 1.00 D of emmetropia; 26% were undercorrected and 16% were overcorrected by more than 1.00 D. Uncorrected visual acuity was 20/40 or better in 76% of eyes. The operation was more effective in eyes with a preoperative refractive error between −2.00 and −4.37 D. Between 1 and 3 years after surgery, the refractive error changed by 1.00 D or more in 12% of eyes, indicating a lack of stability in some eyes. In the 435 eyes, there was a small number of complications including six eyes that lost two or three lines of best-corrected acuity, 16 that experienced vascularization of the incisions, 2 that had delayed bacterial keratitis, and 4 that had recurrent epithelial erosions.

Original languageEnglish (US)
Pages (from-to)1339-1354
Number of pages16
Issue number10
StatePublished - 1987
Externally publishedYes


  • astigmatism
  • clinical trial
  • cornea
  • myopia
  • radial keratotomy
  • refractive keratoplasty

ASJC Scopus subject areas

  • Ophthalmology


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