Additionally, 70% had flattening of their steep anterior corneal curvatures (decreases in average and maximum keratometric values), and 65% had an improvement in visual acuity. The initial pilot study enrolled 16 patients with rapidly progressing keratoconus and all of the patients stopped progressing after treatment. Human studies of UV-induced corneal cross-linking began in 2003 in Dresden, and early results were promising. Safety studies showed that the endothelium was not damaged by the treatment if proper UV irradiance was maintained and if the corneal thickness exceeded 400 microns. The investigation also proved that treated corneas contained higher molecular weight polymers of collagen due to fibril crosslinking.
The resultant corneas were shown to be stiffer and more resistant to enzymatic digestion. UV light was used to induce collagen cross-linking in riboflavin soaked porcine and rabbit corneas via the oxidation pathway. The bases for the currently employed corneal collagen cross-linking techniques were developed in Europe by researchers at the University of Dresden in the late 1990s.
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In the pathway most relevant to this topic, oxidation has been shown to be able to trigger corneal crosslinkage through the release of oxygen free radicals. Glycation refers to a reaction seen predominantly in diabetics that can lead to the formation of additional bonds between collagen.
While crosslinking tends to occur naturally over time, there are other pathways that mean lead to premature crosslinking. It has been hypothesized that this natural cross-linkage of collagen explains why keratectasia (corneal ectasia) often progresses most rapidly in adolescence or early adulthood but tends to stabilize in patients after middle-age.
In the cornea, collagen cross-linking occurs naturally with aging due to an oxidative deamination reaction that takes place within the end chains of the collagen. Carus University Hospital, Dresden, Germany Study Ĭorneal collagen crosslinking (CXL) is a minimally invasive procedure used to prevent progression of corneal ectasia such as keratoconus and post-LASIK ectasia.Ĭross-linking of collagen refers to the ability of collagen fibrils to form strong chemical bonds with adjacent fibrils. 8.3 Ectasia following Refractive Surgery.6.1.1.2 Epithelium-on method / Trans-epithelial method.
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