Crosslinking of the cornea is still a relatively new method. It is generally used to treat keratoconus. The procedure was first developed at the end of the 1990s at the Dresden University Eye Clinic. The doctors succeeded in stabilizing the cornea by cross-linking it. The progressive process of corneal protrusion could thus be stopped. Here you will find further information as well as selected crosslinking specialists and centers.
Crosslinking is a safe and successful routine procedure to stabilize the cornea. Doctors use it in particular for progressive keratoconus.
This stabilization is achieved through a photochemical process. When UV light is used, the B2 vitamin riboflavin is activated and oxygen radicals are released. These bind the carbon and nitrogen groups of the collagen fibers of the cornea together. This is also referred to as cross-linking of the cornea. This creates a dense network that stabilizes the cornea.
The vitamin riboflavin used also absorbs UV light. This protects deeper segments of the cornea.
The cost of corneal crosslinking is several hundred euros. In most cases, the costs can be reimbursed by the health insurance company.
Around 40,000 people in Germany suffer from keratoconus. This is a special form of corneal curvature in which the cornea of the eye bulges forward in a cone shape.
The causes of the disease are largely unknown. As keratoconus occurs more frequently within a family, a hereditary predisposition is suspected. Causes could also be
may be the cause.
The disease often occurs at an early age. It can manifest itself during puberty, but usually by the age of 30. Crosslinking of the cornea of the eyes can therefore be an alternative to previous treatment approaches, particularly in young patients.
In keratoconus, the cornea bulges forward in a cone shape © Zarina Lukash | AdobeStock
The most common form of keratoconus is the so-called "Forme Fruste" or silent form. In the majority of cases, it can be corrected with a visual aid and requires no further intervention.
However, if the disease occurs at a very early stage, keratoconus is often progressive. The disease therefore worsens. In this case, glasses are initially recommended to correct the visual impairment. Stable contact lenses that do not put additional pressure on the damaged cornea can also help.
Crosslinking of the cornea is also a possible surgical alternative at the onset of the disease.
However, if the bulging of the cornea continues to increase, the cornea becomes thinner and can break through or scar.
Visual acuity suffers permanently and the deterioration continues despite glasses or contact lenses. The perception of
can be further signs of keratoconus.
Initially, keratoconus occurs unilaterally, but spreads to the other eye as the disease progresses. Especially in the advanced stage, treatment with crosslinking plays an important role.
At the beginning of the disease, keratoconus can only be diagnosed with certainty using medical technology. In addition to the general ophthalmologic examination, the doctor uses various methods. The aim is to measure the cornea exactly and determine its thickness precisely. This is also important for subsequent crosslinking, as certain conditions must be met for treatment to be successful.
Various measurement methods are used to diagnose keratoconus and to check whether crosslinking is possible. Progressive keratoconus can be detected if the corneal refractive power increases by around one diopter over a period of one year.
Using a so-called Scheimpflug camera, the treating doctor can record the topography of the cornea. He uses the contour lines to calculate the curvature of the corneal surface. It is also possible to measure the corneal thickness and the radii of curvature with such a Pentacam.
Both treatments only take a short moment and are completely painless.
An assessment based on the strength of the spectacles is less reliable. Even preliminary findings should not replace a doctor's assessment before starting crosslinking.
Although the technique allows early detection, keratoconus is often only diagnosed when it is already well advanced. It is then often clearly visible even without aids.
A cure is not yet possible. However, the progression of the disease can be halted.
The progression of the disease is different for each patient. In around 20 percent of cases, the bulging and scarring of the cornea progresses very far. Conventional visual aids and special contact lens designs then no longer help. They have no support and fall out of the eye.
Until now, corneal transplantation was the preferred surgical choice in the advanced stages of keratoconus. However, this form of treatment carries considerable risks.
For example, there is no guarantee that the patient will tolerate the donor cornea. In addition, the healing process usually takes quite a long time. In contrast to crosslinking, a significant improvement in vision only occurs after up to two years.
Corneal transplantation is also often used in young patients. This places high demands on the transplant. Crosslinking, on the other hand, does not require any deeper intervention or foreign material.
Crosslinking now offers a gentle and promising alternative. The aim of crosslinking the cornea is to stabilize it. The correction of defective vision is not the primary objective. However, it is now clear that in many cases, crosslinking slightly reduces the protrusion of the cornea. This also improves vision.
In general, the earlier crosslinking of the cornea is started, the better for the patient. This means that very young patients in particular can benefit from crosslinking treatment.
The visual acuity compensated with glasses or contact lenses should not be less than 0.3.
The cornea should have a thickness of at least 400 µ m. This is the only way to ensure the highest possible absorption of UV radiation by the B vitamin riboflavin. If the corneal thickness falls below the minimum value, damage to the endothelium cannot be ruled out even during the otherwise very safe method.
Other factors that can have an unfavorable effect on the success of crosslinking treatment include
The eye does not need to be opened for crosslinking and can be performed on an outpatient basis .
First, the eye is made insensitive to pain by administering eye drops drop by drop. An eyelid holder is usually used to keep the eye open. The doctor then removes the cornea from above. This is necessary as the epithelium offers a certain degree of protection against UV rays. The vitamin riboflavin could otherwise not penetrate the corneal epithelium and enter the stroma.
After the epithelium has been removed, drops based on the B vitamin are administered into the patient's eyes. Every two minutes or so, 0.1 percent riboflavin is used. This process takes about half an hour.
If the cornea is thinner than the recommended 400 µm, the administration of hypotonic riboflavin may cause the cornea to swell. Cross-linking is then still possible.
Irradiation with UV light during crosslinking of the cornea of the eyes is then carried out on an area of approximately 8 to 9 cm². The areas under the cornea must not be damaged. For this reason, the distance of the UV light to the cornea and the intensity of the beam are adjusted accordingly. This treatment takes about half an hour.
During this time, the vitamin continues to be dripped every two minutes. The doctor will also continuously check the thickness of the cornea during the crosslinking procedure. The surface of the cornea is then rinsed.
Including preparation, crosslinking takes less than two hours.
Immediately after crosslinking, pain cannot be completely avoided. The removed epithelium needs time to heal. Anti-inflammatory antibiotics and steroids are dripped as required for about one to two weeks after the operation.
Following crosslinking, the patient must wear a bandage contact lens for a few days. As long as the healing process of the epithelium is not complete, various side effects such as rubbing or tearing of the eyes may occur in the first two months. Dry eyes and sensitivity to light are more common after crosslinking.
Slight clouding of the anterior stroma is also likely as a result of the procedure after crosslinking the cornea of the eye, but this will disappear within a few months. The eye will also be reddened for about two weeks after corneal crosslinking.
These symptoms are normal and harmless after corneal crosslinking treatment. Regular use of the medication and tear substitutes administered can alleviate the discomfort associated with crosslinking of the cornea of the eyes.
After successful treatment of the eyes, the patient can return to wearing hard contact lenses. This not only improves visual acuity, but also significantly improves quality of life.
As a rule, the first crosslinking treatment is already successful and can stabilize the cornea sufficiently. This is usually followed by a regular follow-up check of the cornea. The ophthalmologist checks the topography of the cornea and the visual acuity of the eyes daily at first, then every three months and later every six months.
In individual cases, a combination of crosslinking and ring implantation is also possible. This can both halt the progressive course of the disease and achieve significant improvements in vision.
During ring implantation, individual rings are inserted into the deeper corneal segments. The strength of the correction is influenced by the length and thickness of the rings. The rings are implanted using a precise laser.
However, such a combination should only be carried out if, in addition to progressive keratoconus, there is also an intolerance to contact lenses.
Crosslinking is generally a very safe method with no major side effects. Compared to corneal transplantation, crosslinking is also considerably less expensive.
Serious complications, such as damage to the retina or the lens of the eye, have not been reported to date. The complication rate of the procedure is less than 3 percent. These complications after crosslinking are essentially limited to
Infections very rarely occur after crosslinking of the cornea.
No permanent damage has been observed to date as a result of crosslinking. Corneal transplantation has also not been necessary in any of the cases treated to date.
The desired stabilization of the cornea was achieved in 98 to 99 percent of the crosslinks performed.
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