title: Intracorneal asymmetrical rings for keratoconus: where should the thicker segment be implanted?
abstract: OBJECTIVE
  To report a 20-year-old man who presented with monocular diplopia in the right eye with uncorrected visual acuity (UCVA) of 0.3 and best spectacle-corrected visual acuity (BSCVA) of 1.0 with -0.50 -3.00 x 45 degrees.
  
  
  METHODS
  Clinical examination and corneal topography revealed grade I keratoconus in the right eye. Intracorneal ring segments (INTACS; Addition Technology, Des Plaines, III) were implanted in May 2004 without surgical complications at 415 microm (70% of the corneal thickness), with the 450-microm segment implanted superiorly and the 250-microm segment inferiorly.
  
  
  RESULTS
  For 2 months postoperatively, BSCVA remained at 0.4 with +1.50 -4.50 x 25 degrees. The segments were reversed, implanting the 450-microm (thick) segment inferiorly and the 250-microm (thin) segment superiorly. One week later, UCVA was 1.0 and remained stable for 3 months after reimplantation.
  
  
  CONCLUSIONS
  This report shows that implanting the thicker segment inferiorly provides better visual results.
authors.affiliation: Vissum Instituto Oftalmológico de Alicante, Department of Refractive Surgery, and Division of Ophthalmology, Miguel Hernández University, Medical School, Alicante, Spain. jlalio@vissum.com
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Alió
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Shabayek
mesh_terms: D000328:Adult; D003319:Corneal Stroma / Q000473:pathology / Q000601:surgery*; D019781:Corneal Topography; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000473:pathology / Q000601:surgery*; D008297:Male; D019736:Prostheses and Implants; D011474:Prosthesis Design; D019919:Prosthesis Implantation / Q000379:methods*; D014792:Visual Acuity