Keratoconus is a disorder (often hereditary) of the cornea in which an abnormality arises in the support tissue (collagen).
The disorder usually occurs on both sides, but often not to the same extent. The abnormality occurs more in men than women and usually from the age of twenty onwards. The progressive thinning of the cornea causes bulging resulting in irregular astigmatism and increasing myopia.
In the first instance this disorder can be rectified using corrective glasses or semi-hard or hard contact lenses. If the abnormality develops further, the only treatment available at present is a cornea transplant.
Recently, new technology has been unveiled which can stop the increasing thinning of the cornea: “ultraviolet crosslink” and a method for normalising the cornea: “intracorneal rings”.
- Ultraviolet crosslink
- Intracorneal rings
THE PRINCIPLE OF THE TREATMENT
First Riboflavin droplets are applied to the cornea, after which they permeate to the deeper layers of the cornea.
Then UV light is applied, upon which a bonding occurs in the cornea among the collagen fibres (cross-linking). This makes the cornea three (3) times stronger. The process stabilises after six months.
Up to now this procedure took more than one hour (30 minutes for the droplets and 30 minutes for the UV light). But thanks to AVEDRO technology, treatment time is reduced to a maximum of 20 minutes for the droplets phase and a maximum of four (4) minutes for UV exposure. This is primarily due to changes in product composition and a greater energy output for the UV source.
An additional advantage is that the therapy can be conducted on a trans-epithelial level so that there is no post-operative pain. The refractive problems caused by keratoconus (myopia –irregular astigmatism) are often treated beforehand with a topography guided Excimer laser or afterwards with a toric phakic intraocular lens implant.
CASES WHERE RECOMMENDED
- preventing the development of keratoconus (KC)
- treating the evolution of keratoconus (progressive form)
- ectasia of the cornea
- instability of the cornea after a radial keratotomy (RK)
- chronic corneal oedema
- persistent corneal ulcer
- recurrent KC after corneal transplant
- slower healing process
- aberrations in healing (a complication markedly lower with the trans-epithelial approach of the AVEDRO therapy)
- post-operative infection
CASES WHERE RECOMMENDED
- corneal thickness of <325µm
- problems with epithelial healing
- herpes keratitis
Keratecasia or a bulging of the cornea is usually the result of keratoconus or can result from refractive surgery.
This progressive bulging of the cornea is usually accompanied by a gradual thinning of the cornea. The symptoms are usually a progressive reduction in sight, a distorted acuteness of vision, and increased sensitivity to light.
In the first stage of ectasia, it is possible to use semi-hard contact lenses, but there is a high risk of a progressive intolerance in the course of time. At present, the only possible treatment is to do a cornea transplant. However, this operation carries a high degree of complications.
As a more recent technique for normalising the shape of the cornea, it is possible to fit intra-corneal ring segments.
This technique, which has been available for over 15 years, is now becoming popular once again because the tunnelling which previously had to be done mechanically can now be carried out with more precision using a ziemer laser.
The final result once the rings have been fitted is supported topographically. It improves the totally irregular shape of the cornea to give the patient a much better quality of life.
The operation is done under local anaesthetic and the patient can leave hospital the same day.
As possible complications we mention the possible repositioning of the ring or a post-operative infection. These complications can be treated quite simply if they are diagnosed at an early stage. The corneal rings need to be modified in 10% of cases. After the operation, the patient may notice momentary irritation, halos, photophobia.