Keratoconus is a noninflammatory condition of the cornea in which the cornea thins gradually and thus takes on the shape of a cone (because of its fragility). See the picture below.
The word "keratoconus" comes from the Greek meaning conical cornea. The cornea is the transparent window in front of the eye. It is on this structure that the contact lenses rest. Any irregularity of the cornea compromises a good vision.
Keratoconus does not necessarily cause blindness, but the fact that myopia and astigmatism are constantly increasing and that this astigmatism is irregular, makes the vision very distorted. The vision with glasses remains mostly very weak because of the irregular astigmatism. This problem is progressive, takes years to fully develop and can stop at any stage.
Keratoconus is well known since the middle of the 19th century. However, the reasons for its development remain obscure. Keratoconus is a subject that is still studied extensively. Some cases of keratoconus have a hereditary component and studies show that about 8% of patients have other affected parents. On the other hand, most cases seem sporadic. It has been suggested that there is less than 1 in 10 chance of having a child with some degree of keratoconus if one of the parents has this condition without any other family history. The current incidence of keratoconus is still uncertain, but large studies estimate its incidence at between 50 and 230 per 1,000,000 people. It appears in all ethnic groups and has a little more association with women.
Keratoconus usually begins at puberty and progresses over a period of 10 to 20 years. Its rate of progression is variable and its severity ranges from mild astigmatism to severe corneal thinning, protrusion and scarring. Keratoconus has been associated with other medical problems including atopic disease, Down's syndrome, Ehlers syndrome -Danlos syndrome, Marfan syndrome, cranio-facial dysostosis and osteogenesis imperfecta.
At first, patients notice blurred vision and visual distortion. This can be accompanied by photophobia (sensitivity to light) and glare problems. Then there are frequent changes in their vision and patients often have to change glasses prescription. In a more advanced stage, there will be a rapid decrease in vision because of the fog that forms in the cornea. Often, the cornea will become opaque because of the significant scarring of the tissue.
The treatment of keratoconus depends on the severity of the condition. Initially, glasses can correct myopia and astigmatism with some success, however, as the disease progresses, only rigid contact lenses can give optimal correction. Today, there are more and more options for contact lenses for keratoconus.
Finally, when good vision is no longer possible even with contact lenses or the individual develops lens intolerance, a transplant cornea will be recommended. Only 10% of people with keratoconus will need a corneal transplant and the success is about 90%.
(Source : Association des Optométristes du Québec)