Keratoconus is a pathology of the eyes. It consists of a deformation of the cornea, which changes from a spherical shape to a conical shape. This deformation is associated with a significant thinning of the cornea.

Keratoconus is a non-inflammatory disease of the eye, in which the affected part is the cornea (kerato meaning “relating to the cornea”). The cornea is the transparent lens that covers the iris and the pupil. In the case of keratoconus, the cornea undergoes a deformation: it takes a cone shape (instead of its normal rounded shape) and becomes increasingly thin and irregular. The disease is not contagious and usually affects the two eyes in different ways. It occurs gradually.

The disease usually begins at the end of adolescence, between the ages of 10 and 20 in 82% of cases. It can also occur later in life. It concerns both men and women. Often isolated, it can be associated with other eye pathologies or rare genetic diseases such as trisomy 21. Keratoconus affects 1 in 2 people.

Although the disease has been known for almost 300 years, its causes are still unknown. We speak in this case of idiopathic disease. The mechanism would consist of an excessive and abnormal degradation of the collagen which constitutes the base of the tissue of the cornea.

It is likely that this is a genetic disease, although no gene has yet been identified. Research is underway. This hypothesis is supported by the fact that often several members of the same family are affected by the disease. Indeed, there is a family history of keratoconus in 20% of cases.

Environmental factors are probably associated with the genetic predisposition. It is also very likely that hormones at the time of puberty come to play a role in the development of the pathology. The presence of an allergic ground is found in half of the patients.

Keratoconus causes vision disorders such as blurred vision, impaired distance vision or even duplication of images. It significantly impacts and reduces vision. It affects both eyes in 90% of cases. Keratoconus is often discovered during an ophthalmologic assessment for a loss of vision that cannot be corrected by glasses. The ophthalmologist often notices an abnormal corneal topography.

The first symptoms of keratoconus are:

• blurred vision (feeling of fog), most often in distance vision (myopia) and / or distorted vision (astigmatism);
• excessive sensitivity to light, glare;
• eye irritation (watery eyes);
• vision poorly corrected by conventional glasses;
• difficulty adapting to lenses;
• Difficulties in night driving;
• visual fatigue, headaches.

There are four clinical stages, making it possible to assess the course of the disease, from the least advanced to the most advanced:

• the infra-clinical or latent stage: no clinical sign or impact on vision;
• the rough stage: presence of fine clinical signs without impact on vision;
• the proven stage: important clinical symptoms with repercussions on vision;
• the complicated stage: vision deteriorates despite good management, often involving the realization of a cornea transplant.

Progress from one stage to another is unpredictable and may not happen at all. Some patients develop severe forms very quickly, while others do not pass the least advanced stage. Keratoconus is often asymmetrical, that is, it does not affect both eyes the same way.

All mechanical attacks on the eye can aggravate the disease and should therefore be avoided, such as rubbing the eyes for example. Laser surgeries for myopia are contraindicated.

Make glasses

The first treatment will be to have glasses made to correct the vision problems. This is sufficient for about 15% of patients. In case of failure, the glasses are adapted into lenses. These allow to come to attenuate the irregularities of the cornea. It is the most used treatment, since it concerns half of the patients. To stabilize the vision, in the event of progressive disease only, it is also possible to carry out a crosslinking of the corneal collagen. The procedure consists of surgical scraping of the cornea followed by treatment with vitamin B2 and UV.

Corneal surgery operation

If this is not enough or is not possible, the treatment will be corneal surgery. This is the case for a quarter of patients. There are several options:

• intra-corneal rings: these are small plastic semicircles that will be inserted into the thickness of the cornea to strengthen it;
• anterior deep lamellar graft: this surgery consists of leaving the posterior part of the cornea in place and replacing only the stroma (the anterior part that is the most damaged in keratoconus);
• cornea transplant: the operation involves removing most of the damaged cornea and replacing it with that of a deceased donor. This operation is the last resort and concerns only 1% of patients.