title: Wavefront aberrations associated with the Ferrara intrastromal corneal ring in a keratoconic eye.
abstract: OBJECTIVE
  To describe the optical implications of the aberration pattern of a keratoconic eye implanted with an intrastromal corneal ring (Ferrara ring).
  
  
  METHODS
  A 32-year-old man with bilateral keratoconus had a Ferrara intrastromal corneal ring implanted in his right eye. Surgery was uneventful and both uncorrected (UCVA) and best spectacle-corrected (BSCVA) visual acuity improved. Corneal topography was performed before and after surgery. Wavefront measurements were performed 1 month after the procedure in both eyes for comparison. The point spread function, modulation transfer function (MTF), and convolved acuity chart were analyzed.
  
  
  RESULTS
  The right eye--implanted with the intrastromal Ferrara ring--had high root-mean-square (RMS) values for higher order aberrations. The left eye-keratoconus without an intrastromal ring-had moderate values. Point spread function, MTF, and convolution acuity charts are presented for each eye, with the latter two showing improved visual function in the implanted eye, despite a higher aberration value.
  
  
  CONCLUSIONS
  The wavefront measurement device captured aberrations even in a highly aberrated eye. Despite better UCVA and BSCVA, the Ferrara ring notably increased higher order aberrations compared to the fellow eye, but with a more uniform central pattern. In this case, the larger RMS value was a poor predictor of good visual function; other metrics better predicted the patient's subjective response. Metrics other than RMS error may be necessary to better correlate aberration value with visual satisfaction in some eyes.
authors.affiliation: Cole Eye Institute, Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH 44195, USA.
authors.forename: Maria Regina
authors.initials: MR
authors.lastname: Chalita
authors.forename: Ronald R
authors.initials: RR
authors.lastname: Krueger
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000175:diagnosis / Q000503:physiopathology; D003319:Corneal Stroma / Q000503:physiopathology / Q000601:surgery*; D019781:Corneal Topography; D006801:Humans; D007640:Keratoconus / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D019904:Polymethyl Methacrylate; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D012029:Refraction, Ocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology
chemical_list: D019904:Polymethyl Methacrylate