title: Design features of the prospective evaluation of radial keratotomy (PERK) study.
mesh_terms: D002986:Clinical Trials as Topic; D003315:Cornea / Q000601:surgery*; D006801:Humans; D008722:Methods; D011184:Postoperative Period; D011446:Prospective Studies; D012107:Research Design; D014481:United States; D014792:Visual Acuity