Parasurgical therapy for keratoconus by riboflavin-ultraviolet type A rays induced cross-linking of corneal collagen: preliminary refractive results in an Italian study

J Cataract Refract Surg. 2006 May;32(5):837-45. doi: 10.1016/j.jcrs.2006.01.091.


Purpose: To assess the effectiveness of riboflavin-ultraviolet type A rays induced cross-linking of corneal collagen in reducing progression of keratoconus and in improving visual acuity in patients with progressive keratoconus.

Setting: Department of Ophthalmology, Siena University, Siena, Italy.

Methods: This was a second-phase prospective nonrandomized open study. Starting in September 2004, 10 eyes of 10 patients (mean age 31.4 years) with bilateral keratoconus were treated by combined riboflavin-ultraviolet type A rays (UVA) collagen cross-linking. Radiant energy was 3 mW/cm2 or 5.4 joule/cm2 for a 30-minute exposure at 1 cm from the corneal apex. A complete ophthalmologic examination (uncorrected visual acuity [UCVA], sphere spectacles corrected visual acuity (SSCVA), best spectacle-corrected visual acuity [BSCVA]) was performed. Patients had corneal computerized topographic examination, linear scan optical tomography, endothelial cell count, ultrasound pachometry, intraocular pressure (IOP) evaluation, and HRT II system confocal microscopy at 1, 2, 3, and 6 months. After treatment, eyes were medicated and dressed with a soft contact lens.

Results: Comparative preoperative and postoperative results showed increases of 3.6 lines for UCVA (P = .0000112), 1.85 lines for SSCVA (P = .00065), and 1.66 lines for BSCVA (P = .00071). Topographic analysis showed a mean K reduction of 2.1 +/- 0.13 diopters (D) in the central 3.0 mm. Statistical analysis of IOP and endothelial cell count did not show significant differences. Topo-aberrometric analysis findings of corneal symmetry showed a trend toward increasing corneal symmetry with a major reduction in asymmetry between vertical hemimeridians.

Conclusions: Refractive results showed a reduction of about 2.5 D in the mean spherical equivalent, topographically confirmed by the reduction in mean K. Results of surface aberrometric analysis showed improvement in morphologic symmetry with a significant reduction in comatic aberrations.

Publication types

  • Clinical Trial, Phase II

MeSH terms

  • Adult
  • Cell Count
  • Collagen / metabolism
  • Collagen / radiation effects*
  • Cornea / drug effects
  • Cornea / metabolism
  • Cornea / radiation effects*
  • Corneal Topography
  • Cross-Linking Reagents / radiation effects*
  • Endothelium, Corneal / cytology
  • Female
  • Humans
  • Intraocular Pressure
  • Keratoconus / drug therapy*
  • Keratoconus / physiopathology
  • Male
  • Microscopy, Confocal
  • Photochemotherapy*
  • Photosensitizing Agents / therapeutic use*
  • Prospective Studies
  • Riboflavin / therapeutic use*
  • Treatment Outcome
  • Ultraviolet Rays
  • Visual Acuity / physiology


  • Cross-Linking Reagents
  • Photosensitizing Agents
  • Collagen
  • Riboflavin