WHAT IS KERATOCONUS?
Keratoconus is a condition affecting the cornea, the clear front window of the eye that normally focuses light allowing you to see clearly. In keratoconus, the cornea becomes progressively thinner and protrudes, causing distortion of your vision.
Keratoconus is an uncommon condition, affecting about 1 in 2000 people. It is often diagnosed in the teenage years and gradually progresses until a person reaches their late 30s or 40s when the condition tends to stabilise.
WHAT ARE THE SYMPTOMS?
Keratoconus is usually present in both eyes, although it may be worse in one eye than the other. The symptoms include:
- blurred vision and distortion
- frequent changes in glasses or contact lens prescriptions with an increase in myopia (short sightedness) and astigmatism (corneal irregularity)
- occasionally, rapid progression of keratoconus can lead to sudden swelling and ‘whitening’ of the cornea leading to a sudden reduction in vision, light sensitivity and a red eye. This is caused by a tiny break in one of the layers in the cornea allowing the cornea to swell. It gradually heals over several months and leaves a scar on the cornea
WHAT CAUSES KERATOCONUS?
The cause of keratoconus is still unknown. There are several risk factors that have been found to be associated with the condition, for example:
- excessive eye rubbing
- a history of allergy
- a family history of keratoconus
HOW IS KERATOCONUS DETECTED?
The diagnosis of keratoconus is made by an examination of the eye, including taking images of the front of the eye which look at the shape of the cornea (corneal topography). Changes over a period of time in the glasses prescription and in the corneal topography help us determine if your keratoconus is progressing. A regular comprehensive eye examination (at least yearly) is therefore important.
Glasses in the early stages of keratoconus may be sufficient to improve the vision to an acceptable level. However, as keratoconus progresses, rigid, gas permeable contact lenses may be required. In the most advanced stages, a corneal transplant may be necessary if there is significant corneal scarring and /or a contact lens cannot be fitted to improve the vision.
Whilst there is no cure for keratoconus, people with progressive keratoconus may be suitable for corneal collagen cross-linking. This is a treatment that may stop the progression of keratoconus. Eye drops may also be prescribed if there are symptoms of allergy. It is important to avoid rubbing the eyes as this may cause keratoconus to progress.
CORNEAL COLLAGEN CROSS-LINKING
Cross-linking is a treatment for keratoconus that involves the use of riboflavin (vitamin B2) and ultraviolet A light. It strengthens the bonds between collagen fibres in the cornea. A decrease in the strength of these bonds is thought to be the cause for the thinning and protrusion seen in keratoconus. Research has shown that corneal cross linking can stop the progression of keratoconus in most cases, with over 80% of people who undergo cross-linking treatment remaining stable for at least 5-7 years. However, longer term results are not yet known. It is also important to understand that it is not a cure for keratoconus.
Cross-linking is performed as a day procedure under local anaesthetic drops and takes a little over an hour. The first step involves removing the top layer of the cornea (the epithelium). Riboflavin eye drops are then instilled in the eye for 30 minutes, followed by ultraviolet light for a further 30 minutes. A bandage contact lens is placed in the eye at the end of the procedure.
Dr Chan has given a detailed lecture on cross-linking for Keratoconus Australia which is available via their website: www.keratoconus.asn.au