Indução de ligações covalentes do colágeno (cross-linking) da córnea para estabilização da ectasia progressiva

Abstract

ABSTRACT The induction of corneal collagen cross-linking by ultraviolet radiation (UV) over a substract of riboflavin was popularized and dubbed as CXL (corneal cross-linking). In 2003, this technique was introduced in the therapeutic arsenal for patients with keratoconus, aiming to halt the progression of the disease. The procedure would enhance biomechanical and biochemical corneal stability by the formation of new covalents bonds in the amino-termial sites of the collagen molecule of the anterior stroma. Such induction depended on the hydrogen singlets free radicals generated by the riboflavin photosensibilization by UV-A. CXL is indicated in corneal thinning and progressive ectasias, as it happens in keratoconus, post-LASIK ectasia and pellucid marginal degeneration. Other anecdotic indications are described in the literature such as treatment of infectious keratitis, control of bullous keratopathy and corneal melting; however, they will not be discussed in this review. The CXL for the treatment of progressive corneal ectasia is a procedure that does not involve sophisticated equipments. It is safe (low odds of complications), not expensive and with high efficacy (halting the progression of ectasia). The great majority of treated patients are young adults. There are some contraindications for this procedure such as minimum corneal thickness of 400 µm, which is the most feared. The classic technique was described in 1995 by German researchers and variations of this technique still under evaluation. The CXL is a recent procedure and, besides some favorable results, a long-term follow up (more than 5 years) is needed, to evaluate collateral side effects and potential complications.