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From the sixth postoperative month, the corneal power tended to decrease continuously with respect to preoperative data.
Chicago-Collagen cross-linking with riboflavin and ultraviolet A (UVA) light appears to be a safe procedure to stabilize severe keratoconus and reduce the aberrometric comatic component, based on the 1-year experience, according to Elena Albé, MD, who spoke at the annual meeting of the American Society of Cataract and Refractive Surgery.
The procedure includes the application of 2% pilocarpine drops to reduce the probability of any change in lens and retina, the administration of anesthetic medication 30 minutes beforehand, and the application of oxybuprocaine HCl 0.2% 5 minutes before the procedure. Corneal epithelium is removed with a brush (Amoils Epithelial Scrubber, Innovative Excimer Solutions) and then a riboflavin 0.1% solution (10 mg riboflavin-5-phosphate in 20% dextran-T-500 10 ml solution) is applied every minute for 30 minutes. The absorption of the riboflavin is checked in the anterior chamber.
UVA light irradiation is applied over the central 7.5 mm-diameter cornea using a homogenized radiation system (UV-X, Peschke Meditrade GmbH). Exposure lasts for 30 minutes, during which time riboflavin solution is applied again, this time once every 5 minutes. Levofloxacin eye drops then are instilled, and a bandage soft contact lens placed.
Dr. Albé and colleagues carried out a retrospective, non-randomized, single-center clinical study that included 28 eyes of 20 men and eight women (aged 24 to 52 years) with progressive advanced (stage 3) keratoconus. The progression of keratoconus was documented by serial differential corneal topographies and optical pachymetries.
Patients were included in the study if progression of keratoconus had been identified within the previous 6 months by an increase in myopia and/or induced astigmatism of 3 D or more, if there was a change in the mean central K reading of 1.5 D or more observed in three consecutive topography measurements, and if there was a mean decrease in the central corneal thickness of 5% in three consecutive tomography measurements.
The investigators evaluated the intraoperative and postoperative topo-aberrometric outcomes and the refractive and tomographic outcomes 1 year after the procedure. The results were compared to the contralateral untreated eyes with stage I and II keratoconus.
One year after the cross-linking procedure was performed, Dr. Albé reported that the uncorrected visual acuity (UCVA) tended to increase from 0.15 to 0.25, and the best spectacle-corrected visual acuity (BSCVA) tended to increase from 0.45 to 0.65. Topographic astigmatism decreased from 4.76 to 4.44 D, and subjective astigmatism decreased from 3.03 to 2.91 D. Wavefront analysis showed that coma also decreased from 0.90 µm to 0.76 µm.
Cone area, cone diameter, apical keratometry, and curvature gradient did not progress at 1 year follow-up. No significant change was observed in the endothelial cell count 1 year after the procedure.
"Immediately after the cross-linking procedure, we saw a dramatic change in corneal power compared with the preoperative topographic data obtained before epithelial removal, thus demonstrating the important role of corneal epithelium in masking the true steepness of keratoconus," she said. "However, from the sixth postoperative month, the corneal power tended to decrease continuously with respect to the preoperative data."