Keratoconus (KC) is an often congenital, bilateral and hereditary disorder of the eye in which the normally round cornea thins and begins to bulge into a cone-like shape. This cone shape deflects light as it enters the eye on its way to the light-sensitive retina, causing distorted vision. Keratokonus can also be caused by previous eye interventions such as laser treatments of the cornea (Lasik) or by extreme eye rubbing in patients with allergies.
The increasing protrusion (conus) and thus the central thinning of the cornea, lead to a reduction of the visual acuity. Those affected often notice increased glare sensitivity, halos (rings of light around the light source), poor night vision, eye redness or swelling. In addition, visual aids (glasses / contact lenses) have to be readjusted at ever shorter intervals due to an increasing astigmatism of the cornea and are unable to provide full visual acuity.
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At the onset of the disease, keratoconus usually produces no symptoms and is indistinguishable from a normal corneal curvature corrected by a spectacle lens for the patient. Therefore, these diseases of the cornea are usually discovered randomly during a normal ophthalmological examination. When this happens, the disease must be regularly checked by a doctor, and monitored using the cornea topography (Pentacam).
Progressive Form: This is aggressive and can produce symptoms over time. With the progression of the disease, the correction of visual acuity by means of spectacle lenses and contact lenses becomes more and more difficult, because the bulging of the cornea is irregular.
If the protrusion of the cornea increases further, then the time comes when visual aids can no longer be worn because they do not improve vision. In addition, the cornea threatens to break through the permanent central thinning and when this happens, the cone, the thinnest point with the largest protrusion, shifts within the cornea, breaks, produces a scar and irreversibly reduces the visual acuity.
The only treatment option so far was to remove the diseased cornea and replace it with a donor cornea (corneal transplantation / keratoplasty). However, such an operation is organ transplantation with the associated risks and complications and adequate vision is often not achieved.
Crosslinking is a method of mechanical stabilization of corneal tissues and is achieved by a combination of UV irradiation with administration of riboflavin eye drops (vitamin B2). The intensity of the UV radiation is chosen so that the underlying eye structures are not affected. Both the eye lens, as well as the retina thus takes no harm in the Crosslinking therapy.
The procedure can be performed on an outpatient basis, takes approximately 30–60 min with preparation and is done under local anesthesia. In a first step the uppermost layer of the cornea, the epithelium, is removed. This is necessary so that the riboflavin eye drops (vitamin B2) can enter the cornea. At a less advanced stage, the epithelium may be unaffected (transepithelial crosslinking). Subsequently, the cornea is treated with UV-A light. Finally, the eye gets antibiotic eye drops and tear substitutes for better wound healing.
Goal of therapy
The aim of the therapy is to stabilize the protrusion and thinning of the cornea. The disease can not be reversed, but at best „frozen“. In individual cases, further cross-linking may become necessary for stabilization. If no progression is shown over time, an intraocular contact- lens (ICL) can offer the best vision results.
After the procedure
In the first 24 to 48 hours, topical pain is normal, but it disappears completely afterwards. For relief, every patient gets eye drops and tear substitutes. The vision may be temporarily slightly limited, but increases significantly after a short time after the therapy. Often one also achieves an increase in the visual performance, which, however, is individually different and not guaranteed.
A long-term supply with an intraocular contact lens (VisianICL) is the best possible correction option. The vision is better than with glasses or conventional contact lens.