British Contact Lens Association

Contact lenses and keratoconus

Keratoconus is an eye condition in which the cornea (the transparent front of the eye) distorts to become cone-shaped rather than having a regular shape. It’s a rare condition affecting between one in 3,000 and one in 10,000 people depending on where they live. It usually occurs in both eyes, although one eye is normally affected before the other, and the cause is not fully understood.

Contact lenses play an important part in managing keratoconus. The first line of management is usually to correct the irregular cornea with rigid gas-permeable (RGP) contact lenses although some people with early keratoconus may be able to wear glasses or soft contact lenses. Contact lenses do not slow down the rate of progression of the cone but they do give good vision which could not otherwise be achieved. Between 10-20% of those affected by keratoconus go on to need corneal surgery. New procedures to stabilise the cornea at an earlier stage are also showing promise.

RGP corneal lenses work by trapping a ‘liquid lens’ between the cornea and the lens that effectively neutralises the irregular front surface of the eye. There may also be a contact zone which compresses slightly on the cornea, so that it takes up the regular shape of the back surface of the lens. There are many specialist keratoconic designs available.

Some soft lenses have been designed especially for keratoconus in recent years. These are thicker than regular soft lenses so they retain a more rigid shape. Another alternative is combination rigid / soft lenses: either a ‘piggy-back' fitting with an RGP lens fitted on top of a soft lens, or a ‘hydrid’ design which has an RGP centre with a soft surround.

The other option is scleral lenses which, as the name suggests, fit onto the sclera or white of the eye and do not touch the cornea. Like RGP lenses they provide good vision by holding a lkiquid lens against the eye to neutralise irregularity. They are larger than corneal lenses, up to 23-25mm in diameter, and are made of gas-permeable materials. Despite their size they are very comfortable and have the advantage that they don’t fall out – an issue with some corneal lenses for advanced keratoconus. These lenses are sometimes used for other medical indications such as severe dry eye or drooping eyelid.

Comparison of a scleral lens for keratoconus (left) and a regular RGP lens (courtesy of Ken Pullum and the Keratoconus Group)

If you have keratoconus, your BCLA contact lens practitioner will advise you on the best form of correction for your eyes or refer you for specialist advice