Keratoconus is a degenerative corneal condition that affects about 1 in 2000 people in the UK. The cornea, which is the clear window at the front of the eye, progressively thins and due to the internal pressure of the eye it bulges out to form a cone like shape, hence the name keratoconus. The mechanism by which this happens is only just becoming clearer and it is likely to be multifactorial. There is no significant heredity element, however, having a family member with the condition is a predisposing factor. The condition is usually bilateral but can often be much worse in one eye over the other.
Other predisposing factors include atopic disease (allergies, excema, asthma, etc), diabetes, excessive eye rubbing and certain underlying conditions such as Downs Syndrome. There are hotspots throughout the globe suggesting a hereditary and racial element to the disease, for instance there are larger numbers of keratoconic sufferers with an Asian background, specifically those from the northern regions of Asia such as Pakistan.
What is keratoconus?
Keratoconus is a degenerative condition which causes a bulging of the corneal shape giving it a rugby ball shape compared to that of a normal eye which should be almost spherical. The mechanism for this shape change is still a matter of debate, however, what we do know is that the cornea thins and bulges creating a cone like shape (see OCT section). This induces an irregular astigmatism which causes the reduced vision.
The cornea forms about 80% of the eyes focusing power, therefore, any inconsistencies in it's shape, even a very small one, can have a dramatic affect on the focus of the light onto the retina and therefore, the level of vision. Typically an eye affected by KC sees shadowing of images and suffers with glare (see opposite).