UV crosslinking of the cornea represents a new treatment method based on molecular cross-linking of corneal collagen. The biomechanical properties of the cornea are primarily determined by the collagen fibers and the degree of interfibrillar linkage. The treatment technique involves the use of UV light and riboflavin (vitamin B2, a non toxic photosensitizing solution) for inducing cross-linking to increase biomedical rigidity of the cornea. This allows, in case of keratoconus, to slow down or even to stop the progressive thinnening of the cornea.
The aim of the uv cross-linking treatment is to rise the biomechanical and biochemical stability of the tissues; biomechanical by increasing the interfibrillar linkages of the collagen and biochemical by increasing the resistance to enzymatic digestion. The treatment allows stabilizing and solidifier the cornea, intends to postpone the point of time where corneal transplantation becomes necessary in patients with keratoconus, and in some cases, even to avoid surgery. Keratoconus is a no inflammatory ectasia of the cornea. In general, keratoconus affects both eyes and leads to a progressive irregular deformation of the cornea caused by reduced stiffness of the corneal rigidity. This corneal deformation goes together with a drastic impairmement of vision ability.
The UV cross-linking was pioneered in 1997 by Professor Seiler and his team, in Dresden in Germany. In a clinical study, they followed 26 eyes of 25 patients with progressive keratoconus. In all cases, only one eye was treated, the other one was used as a reference. The treatment technique involved abrasion of the central epithelium in an area of 9 mm in diameter and application, for 10 minutes, of nontoxic photosensitizing riboflavin. Afterwards, the cornea is irradiated with 365 nmUV-A light for 30 minutes.
This study has shown that the keratoconus’s progression was stopped in all cases, no side effects, no side effect was observed and the evaluations shows no changes in endothelial cell density and corneal transparency. Maximal keratometry readings were reduced by an average of 2 diopters in 70% of the eyes and the best visual acuity improved in 65% of the patients. In all cases, the epithelium healed uneventfully, and serial topography at 6-month intervals showed no progression of keratectasia during a mean follow-up ( range 1 to 4 years). The treated corneas showed an increased stiffness, thickened collagen fibers and an increased resistance against enzymatic digestion.
Other studies have been undertaken, by Dr. Caporossi and his colleagues in Italy, by Dr. Kanellopoulos in Grece and Dr. Boxer Wacher in the States. The results of those studies the follow-up time ranged from two to five years, showed that the combination of riboflavin plus UV irradiation is no harmful and the most effective to increase significantly the corneal rigidity.
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