Corneal Cross-Linking (CXL)

Cross-linking is a method that appeared in many country relatively recently, but it has been used all over the world since 2004. Corneal collagen crosslinking is also known as crosslinking method, CXL method, UV-x-linking, UVA method, C3-R. Its Essence consists in photopolymerization of stromal fibers, which occurs under the combined action of a photosensitizing substance (Riboflavin or vitamin B2) and ultraviolet.

During recent years, there has been a noticeable expansion of cross-linking. For example, it is successfully used to prevent the progression of secondary keratoconus (arising after LASIK iatrogenic keratoectasia), pellucid marginal dystrophy, keratomalacia of various origins. There are preliminary encouraging data on the successful use of cross-linking for the treatment of bullous keratopathy, keratitis and corneal ulcers.

The history of the method

The beginning studies of the photobiology of the cornea refers to 1990. Then a group of researchers has been seeking biological adhesives, activated with heat or light, which reinforce the resistance of the collagen of the cornea (Khaderm, T. Tuong, T. J. Emest, 1994). A bonding effect was found to occur in the elimination of oxygen radicals, the release of which caused the formation of bonds of disparate collagen fibrils.
In the opinion of the researchers, the increased resistance of the tissues of the cornea stop the progression of keratoconus and, therefore, postpones or allows you is to avoid transplantation of the cornea patients.
Pioneers of crosslinking were: Professor T. Zeiler, E. Sporl, Wollensak. The idea of this method arose from Professor Zeiler during a visit to the dentist, after he was put photopolymer seal. In 1994, he led a team of researchers, and work began. The first experiments were carried out on animals, and then – on the donor (cadaver) cornea. After that, the first treatment of patients with keratoconus and other keratoectasia was carried out.

The mechanism of corneal cross-linking

1. Combined effect of Riboflavin and UltraViolet;
2. Release of oxygen radicals;
3. The occurrence of coupling between the carbon base – collagen crosslinking.

Photopolymerization increases the strength of corneal collagen (rigidity) and increases its resistance to keratoectasia. Between collagen fibrils appear new cross-linking, and it increases the strength of the entire cornea.

Indications for CXL

Due to the relative youth of the method and the development of scientific thought, the scope of cross-linking is growing from year to year, its effectiveness is revealed with an increasing number of diseases. Therefore, we present the testimony formulated by Professor Seiler himself at the cross-linking courses during the international Congress in Berlin in September 2008. The crosslinking is recommended in cases:

• keratoconus (KC);
• pellucid marginal dystrophy (PMD);
• iatrogenic keratoectasia due to LASIK surgery;
• кkeratomalacia-melting of the cornea (cornea melting), which occurs, as a rule, due to autoimmune processes;
• bullous keratopathy

Contraindications

• the thickness of the cornea is less than 400 microns in at least one dimension (although it should be noted that this threshold has ceased to be so categorical after the appearance of solutions causing edema of the cornea);
• low visual acuity with correction in the case of keratoconus, even in the presence of adequate thickness of the cornea;
• patient's age is less than 12 years (not olways);
• corneal scars on huge area;
• allergic conjunctivitis.

Procedure

Manipulations are carried out under local anesthesia (drops of Alkaine). Currently, two main techniques are used - traditional and transepithelial corneal crosslinking.

Conventional cross-linking

The operation is divided into 2 stages.

Stage 1: anesthesia Is performed, the spatula deepithelization of the cornea is carried out, and then the solution of Riboflavin is instilled for 25-30 minutes. After that, the doctor using a slit lamp assesses the degree of impregnation of the cornea drug. If the impregnation is sufficient, proceed to stage 2, if not-continue to instill until the desired result.

Stage 2 is to use a beam of ultraviolet light that interacts with Riboflavin, causing crosslinking of corneal collagen. This process also lasts about 30 minutes.

At the end of the operation, the antibiotic and anti-inflammatory drug are instilled, after which the patient is put on a soft therapeutic contact lens.

Transepithelial corneal collagen cross-linking (TE-CXL)

When using this technology, the removal of the top layer of the cornea is not required. He razryhlenija and becomes permeable to Riboflavin using spetsialnogo of the drug (tetracaine). In this regard, the patient is much less pronounced discomfort after surgery, much shorter rehabilitation period and less risk of various complications.

Possible cross-linking complications

For a long time, the complications of cross-linking were not mentioned in the professional literature. For the first time reports covering this topic appeared at the last ESCRS Congress. In our practice of cross-linking we also meet with typical complications:

1. Varying degrees of severity of turbidity of the cornea. The quality of vision is usually not affected, but can be quite pronounced. Most often resorption occurs within 1-6 months, although it happens that this process takes up to 2 years.
2. Eye irritation (1-2 weeks after surgery).
3. Delay in re-epithelialization.
4. Deterioration of the original visual acuity and its gradual recovery. This complication occurs rarely, vision is restored within 1-12 months.
5. Melting of the cornea.
6. Reactivation of herpetic infection, development of herpetic keratitis.

It should be noted that with all these complications, as a rule, it is possible to cope, and the use of transepithelial technology minimizes risks.

Video of the surgery of crosslinking in keratoconus

Results after crosslinking

It should be understood that since cross-linking has been practiced since 2004, full information about all the results, as well as about all the complications, is still unknown. But some conclusions are possible to do already now, in particular with regard to the application of crosslinking in keratoconus. With this method, it is possible to stop the development of the disease – this is the main result. There are no data on the progression of keratoconus after cross-linking surgery to date.

After surgery, 25% of patients have improved visual acuity by 1-2 lines-this is a consequence of the flattening of the cornea. Since the main task facing cross-linking with keratoconus is to stop the development of the pathological process, the effect of improving visual acuity is a pleasant "bonus". It is not yet clear why some patients have it, while others do not, so it is impossible to plan. In addition to this effect, 30% of patients improve the fit of hard contact lenses, which is made possible due to the same flattening of the cornea.

The price of cross-linking (CXL)

The cost of surgery in our specialized ophthalmological center is 34 000 rubles (530$) with the traditional method. With the technology of transepithelial cross-linking, the drug is additionally paid (about 5,000 rubles - 80$).

Feedback from patients after surgery

Below in the comments you can find other reviews of people who have already passed the procedure of corneal cross-linking or leave your own opinion.