In keratoconus, the cornea, which is the clear dome-shaped structure at the front of the eye, bulges forward making the surface of the cornea irregular in shape and distorting vision through the affected part.
The bulging is caused by thinning of the cornea, which weakens the structure and allows the pressure within the eye to push the cornea outwards into the cone-shape that gives the condition its name.
Keratoconus affects one in 2,000 people, although it is more prevalent in Middle Eastern and Asian communities. It is thought that genetics may play a part in its origin. It is more common in people suffering from allergies and asthma (atopic). In Down’s Syndrome the occurrence is one in ten.
Keratoconus normally occurs around puberty, and is usually bi-lateral, although one eye is normally affected more than the other. It can still occur in later life and generally develops over several years. Prognosis is better the later-in-life that it occurs. Natural changes in the stiffness of the cornea post 30 years of age tend to reduce the progression of the cone.
Corneal crosslinking is a fairly new procedure, which can be performed to strengthen the corneal structure and slow down, or even arrest, the development of the cone.
Spectacles can be used in the early stages of keratoconus, but contact lenses are the usual method of vision correction as the cone develops. Traditional gas permeable lenses were at one time the only method of correcting the condition, but soft lenses are now available and, more recently, scleral lenses have come to the market offering the sharpness of vision associated with a gas permeable lens but with comfort levels far greater than previous lenses. There are also hybrid lens designs, which have a gas permeable centre surrounded by a soft skirt to aid comfort.
The correction of keratoconus requires specialist fitting skills, and your practitioner is best placed to advise you as to what type of lens is best for you. Your needs may change as time progresses and will depend on the position and size of the cone, as well as on your personal circumstances.