title: Prospective randomized study of corneal aberrations 1 year after radial keratotomy or photorefractive keratectomy.
abstract: OBJECTIVE
  To evaluate the optical properties of the cornea 1 year after either radial keratotomy (RK) or photorefractive keratectomy (PRK) in a randomized group of patients with low myopia.
  
  
  METHODS
  Ninety-six patients with myopia between -0.75 and -5.00 D were randomized to either radial keratotomy (n = 46) or photorefractive keratectomy (n = 50). Topography maps were obtained 1 year after surgery and analyzed by computation of total corneal wavefront aberration and Zernike polynomial coefficients for pupil sizes of 2, 4, and 6 mm. The 4-mm pupil size was used for optimization of the model.
  
  
  RESULTS
  The total corneal wavefront aberrations after RK and PRK were similar and not statistically different. Wavefront aberrations arising from astigmatism or defocus accounted for approximately 70% of the total wavefront error at all pupil sizes in both groups. All types of aberrations, and in particular spherical aberration, increased significantly with increasing pupil size. Higher-order wavefront aberrations were almost twice as high after RK than after PRK at pupil sizes of 4 and 6 mm. Spherical aberration and coma were slightly higher after PRK than after RK.
  
  
  CONCLUSIONS
  Pupil size had a major effect on corneal aberrations after RK and PRK. The most important aberrations were sphero-cylindrical, in which eyes became significantly more myopic with increasing pupil size. The image forming properties of the cornea are better after PRK compared with RK due to the lesser amount of higher-order aberrations.
authors.affiliation: Department of Ophthalmology, Arhus University Hospital, 8000 Arhus C, Denmark. jesper.hjortdal@dadlnet.dk
authors.forename: Jesper Ø
authors.initials: JØ
authors.lastname: Hjortdal
authors.forename: Hanne
authors.initials: H
authors.lastname: Olsen
authors.forename: Niels
authors.initials: N
authors.lastname: Ehlers
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000175:diagnosis / Q000209:etiology; D019781:Corneal Topography; D005260:Female; D006801:Humans; D007646:Keratotomy, Radial / Q000009:adverse effects; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery; D018903:Photorefractive Keratectomy / Q000009:adverse effects; D011446:Prospective Studies