Prospective Evaluation of Radial Keratotomy: Photokeratoscope Corneal Topography

J. James Rowsey, Hal D. Balyeat, Roy Monlux, Jack Holladay, George O. Waking, Michael J. Lynn, George O. Waring, Wilson McWilliams, William Culbertson, Richard K. Forster, Marguerite McDonald, Herbert E. Kaufman, Bruce A. Barron, Richard L. Lindstrom, Donald J. Doughman, J. Daniel Nelson, Stephen A. Obstbaum, Penny Asbell, David J. Schanzlin, Ronald E. SmithJames J. Salz, William D. Myers, Robert C. Arends, John W. Cowden, Robert L. Stephenson, Paul Fecko, Jerry Roust, Peter R. Laibson, Juan J. Arentsen, Michael A. Naidoff, Elisabeth Cohen

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Preoperative and postoperative corneascope photographs of 368 myopic patients undergoing radial keratotomy in the Prospective Evaluation of Radial Keratotomy (PERK) study were optically scanned and digitized. A highresolution scanning system was developed in order to quantify the preoperative and postoperative corneal shape accurately. Careful analysis of the 72 data points in the nine representative rings demonstrated that corneal topography is best represented by radius of curvature from the center to the periphery. The normal myopic cornea flattens approximately +0.28 mm from the center to the periphery, demonstrating the cornea's aspheric nature. More highly myopic patients in the PERK population (−4.50 to −8.00 diopters [D]) demonstrated corneas that are 0.08 to 0.10 mm steeper than the less myopic population (−2.00 to −3.12 D). Optical zone, patient age, and gender are all correlated to changes in corneal topography after radial keratotomy. In more myopic populations, men have corneas which are flatter than those of women by 0.09 to 0.11 mm in all rings represented on corneoscopy. Highly myopic males also experience more corneal flattening after 3.0-mm optical zone radial keratotomy. Regardless of the optical zone used in radial keratotomy, the resulting corneal topography flattens in all rings. However, the ratio of millimeters of radius of curvature change to diopters of correction is consistent for each ring. The dioptric change observed after radial keratotomy corresponds closely with the millimeters of flattening at the respective rings being examined. The central rings flatten 0.166-mm radius of curvature per diopter of refractive alteration obtained. The largest degree of corneal flattening occurs centrally, 0.72 mm, in the more highly myopic patients who underwent 3-mm optical zone radial keratotomy. The use of smaller optical zones in radial keratotomy produces larger changes in the radius of curvature and, consequently, in the amount of refraction than when larger optical zones are used. When compared with younger patients, older patients with 3.0, 3.5, and 4.0 optical zone radial keratotomies experience more central and peripheral corneal flattening. This study of the corneal topography of the myopic population demonstrates that the refractive change resulting from radial keratotomy is related to alterations in corneal topography. The use of similar modifications of the corneal surface may be effective for newer refractive surgical procedures.

Original languageEnglish (US)
Pages (from-to)322-334
Number of pages13
Issue number3
StatePublished - 1988
Externally publishedYes


  • corneal asphericity
  • corneal topography
  • myopia
  • radial keratotomy
  • refraction

ASJC Scopus subject areas

  • Ophthalmology


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