Early keratoconus responds to corneal cross-linking
November 1, 2005
Siena, Italy—Corneal collagen cross-linking—induced by topical treatment with riboflavin and exposure to ultraviolet A light—appears to be a safe and effective, minimally invasive procedure both to reduce disease pro- gression and improve upon the cornea's optical properties in eyes with early keratoconus, said Aldo Caporossi, MD.
"Further data are needed from more patients followed for longer intervals," said Dr. Caporossi, professor of ophthalmology, University of Siena, Italy.
"We are planning to extend our use of this procedure in patients with early or subclinical keratoconus in order to 'freeze' the corneal tissue and prevent the refractive and biomechanical complications of this disorder," he said. "We feel it may be a good option for those with early disease, and particularly young patients without Vogt's striae, who may be less at risk for developing subclinical stromal haze. We are still investigating this using real time in vivo HRT II confocal microscopy."
Data analyzed from 11 eyes followed for a minimum of 3 months (mean, 8.7 months) show the treatment has been associated with significant improvement in uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA) in all patients along with reduced corneal steepness and improvements in irregularity and coma. The only side effect noted has been transient stromal edema.
The concept for using the riboflavin-UVA regimen to promote therapeutic cross-linking of corneal fibers was introduced by Theo Seiler, MD, PhD, and colleagues at the Technical University of Dresden, Germany, and derives from observations that collagen cross-linking associated with aging or diabetes results in increased biomechanical rigidity of the cornea.
"The cross-linking procedure is designed to address the fact that the biomechanical resistance of keratoconic eyes is 50% lower than that of normal eyes," said Dr. Caporossi.
The Siena group uses a treatment regimen that is a modification of the technique introduced at Dresden. First, the central corneal epithelium is removed (8 mm diameter) using a blunt spatula. Then a solution containing 0.1% riboflavin with 20% dextran is applied for 5 minutes followed by 25 minutes of exposure to UV-A light (370 nm) at a dose of 5.4 J/cm2 .
All of the patients treated so far were contact lens intolerant and had a mean central corneal thickness > 400 µm (range, 406 to 468 µm). Mean baseline IOP was 13 mm Hg and the mean endothelial cell count was 2,198 cells/mm2 . Preoperatively, mean UCVA was 20/154 and mean BSCVA was 20/48.
The safety analyses showed there have been no adverse effects on IOP, central corneal thickness, or endothelial cell count. In addition, there was no change in macular thickness as measured with optical coherence tomography.
Compared with pre-treatment, the group has experienced an average 2-line increase in BSCVA and a 2.4-line improvement in UCVA. The procedure has an excellent safety index (post-BSCVA/pre-BSCVA) of 1.46 and a favorable efficacy index (post-UCVA/pre-BSCVA) of 0.9, Dr. Caporossi reported.