Cornea is the clear and transparent texture through which the light rays enter as the first the eye. It is the gateway to the eye and when the cornea is damaged, the light may deform differently and in some cases very weakly or even not at all.
Keratoconus belongs to the group of ectatic corneal diseases. It occurs in one in every 1000 to 1500 people. The cause of this disease is not fully known but it can be assumed that it is an combination of several factors: heredity, mechanical influences or allergy.
The first symptoms of keratoconus occur in the second decade of life (between 10th and 20th year of age). This disease is predominant in young men. Diagnosis is often linked to other diseases, e.g. atopy, Marfan’s Syndrome, Down’s Syndrome, Turner’s Syndrome.
The development of the disease is linked to increased myopia (negative dioptres) and astigmatism (cylindrical dioptres). However, these cannot really be corrected by using spectacles.
In the past, it was only possible to influence the development of the disease by using hard contact lenses. Today´s treatment options are much wider and their suitability depends on the stage of keratoconus.
Diagnosis plays a key role in detecting keratoconus and its classification into individual stages of progression, of which there are five: the fruste form of keratoconus and stages I to IV. Depending on the stage of development of the disease, we will select the most suitable therapeutic method.
We perform keratoconus diagnostics using several specialised examinations:
– corneal topography
– optical corneal topography using a Scheimpflug camera
1. Corneal Cross Linking (CXL)
It is a therapy, which uses two methods: non-invasive (without abrasion of the corneal epithelium) and mini-invasive (with abrasion of the corneal epithelium). The choice of treatment depends on the results of a thorough examination, analysis of the anterior and posterior surfaces of the cornea, its curvature and its thickness. In the majority of cases, we prefer the method without abrasion, which is less painful for the patient and non-limiting in the post-operative period.
The aim of the CXL method is to stop the progress of ectatic corneal disease and not to compensate the cylindrical defect which results from progression of this illness.
In both cases, the intervention is carried out under topical anaesthesia. In the case of the non-abrasive method, this is mainly used for greater comfort. We apply a riboflavin solution and dextran to the patient’s cornea at two minute intervals until we can biomicroscopically see the penetration of the solution into the anterior chamber. In transepithelial application, this phenomenon is usually observed after a 45 minute application of the solution.
UV-A exposure lasts 30 minutes with the continuous application of the riboflavin solution and topical anaesthetic.
After completing irradiation, in the case of the abrasion method a contact lens is placed onto the eye and covers the eye for the following four days. While the lens is in the eye, the patient receiving home treatment will apply antibiotic drops into the eye five times per day. After removal of the lens from the eye, therapy will move on to local corticoids similarly to transepithelial treatment. Corticoids are applied into the eye for three months. Subsequently, the patient attends regular checkups for six months.
2. Implantation of intrastromal segments (rings)
This is an invasive technique where one or two segments are inserted into approximately 80% of the thickness of the cornea after creating an intrastromal channel. The exact number depends on how large and spread the area of keratoconus is.
This ambulant surgery is preceded by a detailed examination of the cornea and the determination of the number of implants and the place of incision.
The surgery itself takes approximately 25 minutes. At the end of the surgery, the eye is covered with a contact lens which will be removed on the fourth day after the surgery. Post-operative treatment is very short and only lasts seven days. As with CXL, the subsequent monitoring period is six months.
3. Laser correction by corneal topographic finding
In certain forms of early detections of keratoconus it is possible to perform two procedures in one: the treatment of the cornea with the excimer laser, which achieves a correction of the refractive error of the cornea and after that the CXL procedure is carried out (see above). That stabilizes the cornea and stops thereby the progress of keratoconus. This surgery is not suitable for everyone. Restrictions are given by the stage of the keratoconus, the extent of the refractive error and especially the thickness of the cornea.
4. Corneal Transplantations
We performed the first corneal endothelial transplantation in September 2008. Since then, we have also gradually introduced perforation and anterior lamellar transplantation of the cornea into our ambulant surgery.
Depending on findings and the level of damaged part of the cornea, we select the most suitable method, so the eye is burdened least possible and only that part is transplanted, which is really damaged. Therefore, we always consider transplantation through the entire thickness (perforating or only partial), i.e. lamellar, which puts the least burden on the patient’s eyes.
During the first days after the surgery, we monitor the patient in accordance with a scheme stated in advance. Subsequent regular care is carried out by a local ophthalmologist as agreed with us in advance.
So far, we have carried out all transplants under local anaesthetic but, if necessary, surgery may also be carried out under general anaesthesia in our clinic.
We get grafts from the Eye Tissue Bank at the Ophthalmology Clinic of the University Hospital of Královské Vinohrady, Prague, which, in terms of quality, meet the highest requirements of ophthalmological surgeons around the world. In most cases, the waiting period for a transplant is shorter than eight weeks.