Keratokonus and Corneal Cross-Linking /CCL/ the aim of the procedure
Achieving the biomechanical stabilization of the cornea and stopping the progression of the disease. This is a therapeutical procedure for the eye conditions with progressive thinning and softening of the cornea /ectasia/, with the aim to strengthen the mechanical and biochemical stability of the cornea by inducing the creation of additional chemical bonds within the corneal stroma with strictly localized photopolymerization and maximal protection of the surrounding tissue. The term CORNEAL ECTASIA refers to a group of corneal malconditions characterized by weakness of the structure and thinning of the cornea leading to a protrusion, the so-called “conus”, and irregular astigmatism. The changes are progressive, ranging from a decrease in visual acuity and intolerance to the contact lenses all the way to complete intolerance to the lenses and inability to fit and wear them and for the lens to “stay in the eye”.
The ultimate stage of the cornea thinning represents a threat of the perforation of the cornea, and corneal transplantation is unavoidable. The most frequent congenital ectasias are keratokonus and pelusid marginal degeneration, while the acquired ones are post-LASIK, post inflammatory, bulous keratopathy and other conditions of the cornea softening. The most common denominator of all ectasias is reduced biomechanical strength because of the weakening of the interfibrilar connections. The new approach in treating these conditions, CORNEAL CROSS LINKING/CCL/, is focused on the well known pathogenetic mechanism in order to prevent the need for corneal transplantation by strengthening the structures of the cornea and its “stabilization”. The procedure consists of homogenous illumination of the corneal tissue /UVA 370nm/ soaked with solution of riboflavin /vitamin B2/ during 30 minutes, in order to induce chemical mechanisms of strengthening new covalent bonds among collagen fibrillas /increasing the biomechanical strength/.
The procedure is painless and safe. The effect is localized to the anterior part of the cornea. The two aims of treating corneal ectasia are:
1. recovery of visual acuity achieved later by the GP contact lens
2. restoration of the structural integrity of the cornea by corneal collagen cross-linking /CCL/.
The observation showed:
1. Stopping the progression of ectasia
2. Decreasing the regression
3. Improving the tolerance to the contact lenses
4. Decrease in astigmatism
5. Improvement of uncorrected visual acuity
6. Decreasing the probability of the corneal transplantation.
Corneal ectasia, congenital and acquired- keratoconus, pelusid marginal degeneration, iatrogenous keraectasia /post-LASIK, pseudophacic keratopathy after unsatisfactory cataract surgery/ with corneal transplantation prognosis. The procedure is recommended in the earlier phases when the pachymetric value is greater than 400 microns of the corneal thickness. The clinical application of the procedure started in 1998 /Theo Seiler, MD, Zurich/. There are no effects on the intraocular pressure during the procedure. The GP wearing program waits for a minimum of 2 months after CCL, after the re-epithelization and healing of the cornea.