The cornea, which as the window of the eye is limited to the front of the eye, has to be completely evenly curved and fully clear, so that the light rays coming into the retina produce an accurate image. Congenital corneal clouding as well as corneal clouding which appears in early childhood can, due to a decrease of visual acuity, lead to an insufficient development of the visual apparatus, thereby presenting a reason for visual impairment. When corneal clouding appears in early childhood in only one eye, the other eye takes over all the tasks of learning to see and the affected eye stays behind in its development. If corneal clouding in small children is not treated adequately as well early enough, then as of the time a child starts school, the developmental lag is difficult or not at all possible to make up for. It is therefore exceedingly important to prevent the appearance of this so-called amblyopia (weaksightedness).

Corneal clouding can be congenital or can appear during the course of a separate illness. Further causes can be injuries, chemical burns, inflammations and infections. A very common form of corneal clouding, which seldom occurs in industrial nations and very often occurs in developing countries, is caused by a lack of vitamin A which is a consequence of prevalent malnutrition in these countries.

What is corneal dystrophy?

Congenital corneal clouding, or so-called corneal dystrophy, deals with a hereditary disturbance of the corneal metabolism. It can affect all layers of the cornea. Treatment for this illness is the replacement of the central part of the clouded cornea with a donor cornea by way of a corneal transplant (keratoplastic).

What is corneal degeneration?

Corneal degeneration appears mostly as a consequence of other illnesses. These forms of corneal clouding appear, for example, with rheumatic diseases such as juvenile arthritis. Corneal degeneration is also common with further eye diseases that lead to blindness. The cause is the structural change in the corneal tissue, with a gradual storage of various substances, such as the mineral calcium carbonate. In order to attain better vision, in the case of mineral deposits, medication can be administered in combination with laser treatments to reduce cloudiness. If this does not reduce the corneal clouding sufficiently, a corneal transplant, as would be used for congenital corneal clouding, should be considered as the next treatment of choice. The disease keratitis bullosa deals with a degenerative, bubble-formed illness of the innermost corneal layer (endothelium). Damage to the endothelium leads, with advanced progression, to a swelling and clouding of the overlying corneal tissue, and a marked reduction of visual acuity. The sole transplant of the innermost corneal layer can spare the patient a traditional keratoplastic operation and therefore is the treatment of choice in this case.

A corneal disease caused by a lack of vitamin A (keratomalacia) through the undersupply of nutrients to the whole organism, results in conjunctival dryness, night blindness and corneal clouding. Nutritional supplements containing vitamin A can lead to a rapid improvement or healing of the disease. Many developing countries do give adequate  provisions of vitamin A to the population which is why keratomalacia is one of the most common causes of blindness in third world countries. (www.light-for-the-world.org)

Often the only form of treatment for corneal clouding or certain other corneal diseases, is the replacement of the cornea with a donor cornea. The choice of an appropriate donor organ is crucial in this case. There are three basic kinds of such an operation, depending on the type as well as the severity of the presenting corneal disease. Here a donor cornea of complete thickness or alternatively with only the surface layers will be transplanted. One hundred years after the first successful corneal transplant by the eye doctor Dr. Eduard K. Zirm in the year 1905, the operation techniques have been revolutionised many times, enabling many people today to regain their lost vision. Univ.-Prof. Dr. Mathias Zirm was the first to establish the third and newest form of corneal transplant, the corneal endothelial transplant, in Central Europe in 2006. This method replaces only the innermost layer of the cornea so that, for example, with keratitis bullosa a transparent cornea is regained.