A Randomised, Clinical Trial of Corneal Collagen Cross-Linking in Keratoconus

INTERVENTION: corneal collagen cross‐linking. Cross‐linking is a single treatment involving the use of riboflavin and UVA light to increase the strength of the cornea. The cornea is treated with riboflavin drops for 30 minutes followed by exposure to UVA irradiation for a 30 minutes, during which the riboflavin drops are continued. CONDITION: keratoconus PRIMARY OUTCOME: maximum simulated keratometry value measured using computerised videokeratography (Orbscan II; Bausch and Lomb Surgical, Utah. Patients recruited after November 2007 were also imaged with Scheimplug imaging (Pentacam HR, Oculus, Germany) SECONDARY OUTCOME: best‐spectacle corrected visual acuity expressed as logarithm of the minimum angle of resolution (logMAR) corneal thickness at the thinnest point using ultrasound pachymetry (Pachy Meter SP3000; Tomey, Nagoya, Japan), computerised videokeratography (Orbscan II; Bausch and Lomb Surgical, Utah) and Scheimplug imaging (Pentacam HR, Oculus, Germany) endothelial cell density using the SP 2000 Specular Microscope (Topcon Corp, Tokyo, Japan) intraocular pressure using the Tonopen XL (Medtronic, Jacksonville, Florida) and Goldmann applanation tonometer (Haag Streit, Konitz, Switzerland) minimum simulated keratometry value measured using computerised videokeratography (Orbscan II; Bausch and Lomb Surgical, Utah). Patients recruited after November 2007 were also imaged with Scheimplug imaging (Pentacam HR, Oculus, Germany) subjective refraction (sphere and cylinder) performed by trained orthoptists uncorrected visual acuity expressed as logarithm of the minimum angle of resolution (logMAR) INCLUSION CRITERIA: At least one of the following criteria met over the preceding 12 months: an increase of at least 1 diopter in the steepest simulated keratometry reading derived from computerized videokeratography or in the steepest meridian measured by manual keratometry; an increase in astigmatism as determined by manifest subjective refraction of at least 1 diopter; or a 0.1mm or more decrease in back optic‐zone radius of the best fitting contact lens