Keratoconus, the disease
Keratoconus causes increased protrusion and bulging of the cornea which impairs the vision and in many cases may even lead to the need for a cornea transplant and the associated risks. This corneal disease usually occurs on both sides, but the eyes are typically affected to varying degrees and at different time points.
The symptoms of keratoconus include fluctuations in visual acuity despite correction with glasses or contact lenses, seeing rings of light around sources of light (halos) as well as increased sensitivity to light and glare.
One out of every 2,000 people is affected by keratoconus. The causes of this disease are still generally unknown. It tends to run in families, which could among other things indicate a genetic predisposition. It is also found more frequently in people with Trisomy 21 (Down Syndrome). Strong, frequent rubbing of the eyes over the course of many years, e.g. in the case of allergies, is also regarded as a cause of keratoconus.
Correlation with very rare, systemic diseases resulting in abnormality of connective tissue elements such as Leber congenital amaurosis, retinitis pigmentosa and retinopathy of prematurity is under discussion.
A distinction is drawn between the “silent” form of keratoconus (“forme fruste”) and the progressive form. Form fruste occurs ten times more frequently than the progressive form. It usually does not generate any symptoms and must only be monitored by a doctor, not treated, as long as the condition remains stable.
The progressive form of keratoconus is aggressive and may already be noticeable at an early age. As the disease progresses, it becomes more and more difficult to correct visual acuity with lenses as the bulging of the cornea is so irregular. Hard contact lenses work well here as they put pressure on the cornea and can smooth out the most severe irregularities on the surface.
If the bulging of the cornea increases, there comes a point in time at which contact lenses can no longer be worn. As protrusion increases, the cornea becomes ever thinner. It can rupture and scar in the distended area, permanently reducing visual acuity.
For several years now, it has been possible to slow the progression of the disease by implanting intra-corneal ring segments. All efforts are thus focused on retaining the patient’s own cornea as long as possible since the risks posed by the rejection of a cornea transplant should not be underestimated and the service life of a new transplant is limited. Alternatively, or in addition to this, cross-linking of the cornea can be performed, but the indications for this procedure are limited as well. It is not possible to cure keratoconus.
Every cornea transplant poses the potential risk of the donor organ being rejected by the body. The wound area on the operated cornea is very weak after the transplant and the cornea does not heal well. The area will remain a weak spot for the rest of the patient’s life.
Visual acuity fluctuates greatly in the first months after the transplant operation. The “lifespan” of a transplanted cornea is theoretically unlimited for lamellar procedures and averages approx. 10 years for a PKP.