Surgeon reports collagen cross-linking is safe, effective in the long term

BARCELONA — As the interest in collagen cross-linking for treating disorders such as keratoconus and post-LASIK ectasia grows in Europe, an increasing volume of long-term data from pioneers of the technique appears to support its safety and efficacy, according to a speaker here.

"Corneal topography shows that keratoconus progression was halted in every case so far treated. [Keratometry] readings decreased, and along with it, uncorrected vision increased in the majority of cases," Theo Seiler, MD, said at the winter meeting of the European Society of Cataract and Refractive Surgeons.

"Quite unexpectedly, also BCVA (best corrected visual acuity) increased. We learned that this improvement, which surprised us at first, was due to the increased symmetry and regularization of the corneal surface that is produced by the treatment," he said.

Prospective measurements in patients with bilateral keratoconus, in whom only one eye was treated, show that at 1 year the keratoconus index was significantly lower in the treated eye.

Adverse reactions were rare. Haze was relatively frequent, while epithelial healing problems and scars were reported only in a small number of cases.

However, there are questions that need to be answered as surgeons gain more experience with the technique, Dr. Seiler noted.

These concerns include finding out which stage of keratoconus the technique should be used for to get the best results and at which age the technique should be used. Also, it is still unclear in which type of ecstatic disorder — keratoconus, iatrogenic ectasia or pellucid marginal degeneration — the technique would work better, he said.

Another important issue is the choice of optical rehabilitation; spectacles, contact lenses, intracorneal rings and PRK are possibilities. But the best solution has not yet been established.

Surgeons have also been discussing whether the epithelium should be scraped off before treatment. The corneal epithelium represents a barrier for riboflavin penetration, but some have suggested the use of tetracaine or similar substances as an alternative to mechanical abrasion to "digest" the tight junctions between the epithelial cells, he said.

From the beginning of his studies with the technique, Dr. Seiler said he always believed that collagen cross-linking would be safe because it is a physiological process that is well known in diabetes and aging.

As further evidence of the increased biochemical stability of collagen produced by the technique, Dr. Seiler showed the audience an experiment involving two corneal buttons, one of which was previously cross-linked. After 3 days of immersion in trypsin and collagenase solution, the non-cross-linked corneal button was digested by the enzymes. In contrast, in the other corneal button, the cross-linked part of the cornea was not dissolved and the non-cross-linked deeper layer was, Dr. Seiler reported.

"This shows that cross-linking produces increased biochemical stability and therefore better resistance against collagenases in the cornea," he said.