Management of keratoconus

The management of keratoconus has recently received significant progress.

The Institute of Ophthalmic Somain has been involved in these new techniques to help patients with keratoconus to delay the use of penetrating keratoplasty (corneal transplant). For that, it was fitted with special equipment for its support:

• Lamp for VEGA CROSS LINKING to Riboflavin (Ricrolin)
• Module introduction of intracorneal rings Femtosecond laser.

These new treatments are covered by social security.
To optimize the management of patients with keratoconus, we recall the signs that are currently recommended by the National Center for Keratoconus Toulouse / Bordeaux should always seek the advice of a contactologue because most of keratoconus can be adapted: a specific contact lens consultation is present at the Institute for adaptation of keratoconus.

The cross linking to riboflavin (Ricrolin) can stabilize keratoconus and is proposed for patients with keratoconus:

• evolution: evidence for two exams at 6 month intervals
• 14 to 40 years (after keratoconus stabilizes)
• pachymetry with a> 400 at any point of the cornea topography

The rings are discussed for patients not improved or that do not support the lenses and do not have central corneal opacity. This technique has been used since 1997 but has developed so recently with the possibility of the tunnel at the femtosecond laser which makes it very safe. It can delay the transplant and allows a significant improvement in the medium and long term.

Keratoconus is a deformation of the cornea (the transparent covering of the iris and the pupil of the eye) that tapers gradually loses its normal spherical shape and takes a cone shape irregular. Indeed, the word keratoconus, of Greek origin, means "conical cornea". This deformation, often occurring in late adolescence, creates visual disturbances (blurred vision and distorted and poor distance vision) that require specialized lenses. Keratoconus usually affects both eyes, but not with same severity. Keratoconus is not contagious eye disease is a noninflammatory.

 

Fréquency:

There are significant discrepancies in estimates of the number of people with keratoconus, but many studies estimate the prevalence (number of cases in a population at a given time) is between one in 2000 and one in 500. The variations are due to different diagnostic criteria and detection methods, some mild forms of keratoconus can be detected. Also, if it is often isolated, the eye strain may be associated with other more complex diseases.

Affected Population:

Keratoconus equally affects both sexes, regardless of their geographical origin, although it seems that Asians are more affected. Keratoconus is usually discovered at puberty (10 to 20 years), but it can occur at any age (82% of cases begin before age 40, however).

Causes:

The cornea is the transparent lens through which we perceive the colored iris and black pupil center. Normally, the cornea has a regular round shape. In people with keratoconus, the center of the cornea thins and forms a conical protuberance and irregular that disrupts vision. We do not yet know the exact cause of keratoconus, but it is probably a genetic disease: although no specific gene has been, to date, identified the fact that several members of one family can be achieved and the disease almost always develops in both eyes supports the hypothesis of a genetic involvement. A search is underway to identify the potential (s) gene (s) (s) involved. (See the "research" site). In addition to genetic susceptibility, environmental factors are required for the onset of clinical symptoms of the disease. Mechanical stress (as does rubbing your eyes or wearing contact lenses) could contribute to such cause disease. As keratoconus occurs after puberty, hormones could also be involved.

In addition, it is that many patients with keratoconus have a predisposition to allergies, and often develop eczema and / or allergic conjunctivitis. So it seems that there is a link between allergy and keratoconus whose mechanisms are not clearly established.

In addition, keratoconus often occurs in people with other diseases, genetic, ophthalmologic, such as Marfan syndrome, trisomy 21, retinitis pigmentosa or Leber congenital amaurosis (family illness severe eye). Thus, 5-6% of people with Down syndrome have keratoconus. It is not known if these diseases have genetic characteristics favoring of keratoconus, or whether they are directly involved in the pathology.

Symptoms:

The effects of keratoconus vary among individuals and can range from mild to severe. In most cases, both eyes are affected (in 90% of cases) but it is common for keratoconus is diagnosed in one hand, the time to onset in the second eye is highly variable and up to several years .

In the early stages, keratoconus causes blurred vision (sense of fog) and distorted (astigmatism). This decrease in visual acuity is especially felt in far vision (myopia) and is often associated with excessive sensitivity to light (photophobia), a glare and eye irritation (watery eyes). As keratoconus progresses, astigmatism and myopia increasing. As the deformation of the cornea is irregular, vision suffers a large distortion. The view is blurred, similar to what is seen behind a window when it rains a lot. Images can even seem split or multiple.

People with keratoconus often have to change glasses, because they quickly become powerless to correct astigmatism. In advanced stages, the cornea thins and becomes distorted so that the scars appear and opacify, making the view even more trouble. But as the evolution may stop at any time, many patients do not reach such a keratoconus stage.

Evolution:

Keratoconus, often found at puberty, usually develops until the age of 30-40 years before stabilizing. The development is uneven, some keratoconus remained stable for several years, others worsen before stabilizing again. Keratoconus can stop the progress at any stage. Stages of evolution can be classified according to different criteria, but often there are four stages of increasing severity of keratoconus from beginner to stage 1 until keratoconus with corneal opacity in stage 4.

In rare cases (less than 3%), a particular complication, acute keratoconus (hydrops) may occur.
The evolution from one stage to the next is not mandatory and is not linear in time. It is often unpredictable and asymmetrical (only 13% of cases are unilateral). Some patients therefore have severe and rapidly progressive, others keep their lives as a rough and isolated.

It is important to note that the rate of progression of the disease is accelerated by the patient himself when he rubs his eyes frequently. Similarly, all corneal refractive surgery (such as the excimer laser to correct myopia) may worsen the disease or decompensation. As a result, they are strictly against-indicated for this condition.

Treatment:

The chronology usual therapeutic management has initially an equipment and glasses, if that fails, an adaptation of contact lenses. Finally, in case of intolerance or if the vision is still insufficient, the corneal surgery is required.

The latter has two options:

• the most favorable cases can benefit from the establishment of intra-corneal rings.
• more severe cases involving the creation of a corneal transplant.

To give an order of magnitude, about 10% of patients with keratoconus will never be recognized therapeutic applicants, 15% will be equipped with goggles only, 50% will be equipped with contact lenses and 25% receive a transplant cornea.

The lenses are the weapon of choice for most patients with keratoconus. Adaptation is however difficult or even impossible in some cases. It is better to ask to see a specialist in adapting lens (contactologue) and if possible lenses for keratoconus. The advantage of the contact lens compared to glasses is related to the interface that creates the tear film. This erases many of the irregularities of the cornea. Rigid lenses are much more efficient but more complex to adapt. When the lens is not tolerated or more, it is lawful to offer a surgical alternative.
Until a short time only by corneal transplantation surgery was proposed transfixing. We then had to make a total change of the cornea by creating a graft from a deceased donor. In recent years surgery has greatly evolved.

Three new techniques are now available in practice:

• the corneal cross linking,
• the establishment of intra-corneal rings
• anterior lamellar keratoplasty.

Cross linking with riboflavine (Ricrolin):

The corneal cross linking treatment of keratoconus cornéoplastique by changing the corneal collagen. This treatment can stop the progression of keratoconus. It is based on photopolymerization of collagen fibers by the action of ultraviolet radiation on the cornea previously impregnated with riboflavin or vitamin B12 (Ricrolin ®). This surgery is offered simple topical anesthesia (anesthetic drops). It is steeped in the cornea of ​​riboflavin and illuminate the eye with a special lamp to UVA. The act lasts 1 hour and 1 / 2. It sets up a lens end of the procedure and the patient can then go back home after a medical examination. The indications are not too advanced keratoconus (no opacity and central corneal thickness with greater 400microns) that are evolving (2 separate reviews of 6 months are needed to prove it), in patients under 40 years (beyond the keratoconus continues to evolve spontaneously). This technique is performed at the institute since early 2010 in current practice. A new technique of cross linking is being evaluated in patients whose corneal thickness is between 350 and 400 microns which will treat more advanced stages of keratoconus.

The cross linking to riboflavin (Ricrolin) can stabilize keratoconus and is proposed for patients with keratoconus:

• evolution: evidence for two exams at 6 month intervals
• 14 to 40 years (after keratoconus stabilizes)
• pachymetry with a> 400 at any point of the cornea topography

Anterior lamellar transplant:

This surgery involves grafting only the front part of the cornea in keratoconus is sick and leaves in place the back is healthy. Using this technique, there is less rejection and graft survival is prolonged.

Intracorneal rings:

The rings are discussed for patients not improved or that do not support the lenses and do not have central corneal opacity. This technique has been used since 1997 but has developed so recently with the possibility of the tunnel at the femtosecond laser which makes it very safe.

It can delay the transplant and allows a significant improvement in the medium and long term.

The intra-corneal rings are small semi-circular segments rigid PMMA (plastic). Their place in the therapeutic management is between the failure of adaptation in the use of lens and corneal transplantation. They posed for keratoconus in 1997. Rings are introduced in the thickness of the cornea. Intra-corneal rings are designed to strengthen it. Well positioned, they can tighten the central cornea. The importance and the irregularity of the corneal astigmatism is thus reduced.

Two models are sold:

• the INTAC ® (Addition Technology, Keravision, United Kingdom)
• Ferrara rings ® (Mediphacos, Brazil).

The delay in the development of this surgical technique has been linked to the difficulty of making a tunnel manually to establish intra-corneal rings on keratoconus cornea thinned. But the arrival of the femtosecond laser surgery for myopia made simple and automated the creation of a tunnel with no risk of perforation. This technique has become common now since the arrival of the femtosecond laser (we have this equipment at the institute since 2007). This technique can not be offered with an opaque central keratoconus (stage 4) because we can not hope to improve vision due to corneal opacity which interferes in all cases the vision.

Frequently asked questions:

Is this surgery is supported?

Yes this surgery is covered by social security. A request for prior agreement is required from your primary health insurance by the surgeon who will operate for corneal cross linking and the introduction of intracorneal ring. This is not a cosmetic surgery as surgery for myopia and these two techniques can delay a corneal transplant is an action heavy.

How long does it take to hospital for surgery?

The cross linking and the rings are performed in ambulatory surgery. For transplantation, 1 night in hospital is desirable. The procedure itself takes ¼ of an hour for the rings, about 1 hour for cross linking and grafting.