Wavefront aberrations associated with the ferrara intrastromal corneal ring in a keratoconic eye

Maria Regina Chalita, Ronald R. Krueger

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


PURPOSE: 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. CONCLUSION: 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.

Original languageEnglish (US)
Pages (from-to)823-830
Number of pages8
JournalJournal of Refractive Surgery
Issue number6
StatePublished - 2004
Externally publishedYes

ASJC Scopus subject areas

  • Surgery
  • Ophthalmology


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