What is Cross-linking?
Keratoconus is a disease in which the cornea is slightly weakensresulting in a 'cone shaped' forward bulge. This protrusion usually occurs in the inferior parts (lower half) and may lead to astigmatism (of course it is not the only reason for astigmatism).Wearing glasses can help in the early stages or mild Keratoconus, but there has beenno therapy that can slow down the progression of keratoconus so far. Although glasses, contact lenses, and intraocular ringshave been helpful to correct parts of distorted vision,cross-linking isthe onlyprocedurethat halts the progression of keratoconus. In Corneal collagen cross-linking with Riboflavin, or C3-Riboflavin,by increasing the number of bonds between adjacent collagenstrands in the cornea with Riboflavin, the corneal anchors are strengthened.Cross-links of the cornea act like hooks and prevent the protrusion, angularity and irregularity of the cornea.
What is the mechanism of corneal weakness?
Young patients tend to accumulate free radicals of oxygen in their eyes. Normally these free radicals are decomposed by dismutase, superoxide enzyme,and do not hurt the eyes. Some patients fail to produce these protective enzymes and ultimately the accumulation of free radicals damage the corneal tissue and reduce its strength.
How is the operation performed?
The crosslinking procedure takes about 1 hour and is an outpatient procedure.First the surgeon removes the epithelial layer from the cornea,then Riboflavin (vitamin B2) eye drops are appliedto the corneas, after that the ultra violet light (365um) that reacts with the collagen fibers in the cornea will be applied.It has been proved that this simple act increases crosslinking in corneal collagen tissue and can eventually increase its strength. German ophthalmologist were the first to introduce this technique to the world.
What are the results?
The reported observational evidence shows that this operation slows down and halts the progression of keratoconus. In some cases theprogressive condition has been reversed. It has also been observed that this surgery is more effective if accompanied by INTACC, compared to using INTACS alone.Use of lenses after surgery isusually necessary, but it seems that the destruction of corneal tissue is inhibited by his operation.In studies conducted in Europe, the practice has been proven to be safe and effective and in a few year that it is carried out internationally there has been no need forreoperation, however, more long-term studies should be done to evaluate the need for a reoperation.
What are the complications?
In the first few days after surgery, patients may experience blurred vision, tearing, burning, and redness of the eyeswhich usually go away after a few days, but blurred vision may take a few weeks to dissolve. Normally, 1 to 3 days after surgery,patients can resume their routine activities such as reading, driving and other daily activities.
How long has cross-linking been performedin Iran?
Noor Hospital Ophthalmologists, as pioneers of this practice in Iran, have carried outthis technique since approximately 2 years ago.