Overview
Normally your cornea, the thin clear layer over your iris (the coloured part of your eye), has a dome shape, like a ball. Sometimes the structure isn’t strong enough to hold its round shape and it bulges outward, like a cone. This is called ketatoconus.
It is caused by weaknesses in the thin fibres of protein in your eye called collagen, which help hold your cornea in place. If these fibres become weak, they are unable to hold their shape, causing the cornea to become more and more like a cone.
Symptoms of Keratoconus
The exact origin of keratoconus is not fully understood but research shows that it does have a genetic (inherited) basis. If someone in your family has it you may be at an increased risk of getting the condition. It normally presents in teenage years, with early symptoms being increasing levels of astigmatism . It is normally picked up by an optometrist(optician). Regular eye examinations are recommended for all children/teenagers and is free on the NHS for under 16s and anyone under 19 in full time education. Excessive rubbing of the eyes are also thought to cause keratoconus, and it as also though to be linked to systemic conditions such as Down syndrome, Ehlers-Danlos syndrome, osteogenesis imperfecta and retinitis pigmentosa.
Find an optometrist(optician)
If an optometrist (optician) suspects keratoconus they may refer you to a corneal specialist at your local hospital eye department. Astigmatism on its own is normal and children’s prescriptions can regularly change. If you have any concerns about this please speak to the Optometrist/optician that tested yours or your children’s eyes.
Treatment for keratoconus
The main treatment for keratoconus is to try and correct the vision problems caused by the irregular, cone-shaped cornea. At first you might be able to wear glasses, but if keratoconus worsens, you may only be able correct your sight with hard (rigid gas permeable) contact lenses.
Because keratoconus makes your cornea thinner and more flexible, this can also mean that your prescription might change more rapidly and you may need to change your glasses more often.
If glasses are no longer improving your vision, usually the next type of lens you will try are rigid gas permeable (RGP) or "hard" contact lenses.
Hard lenses give a more even shape to your cornea, improving the focusing. RGP lenses are made of strong, breathable plastic. There are lots of different RGP lenses available. Some are specifically designed to fit corneas affected by keratoconus.
Collagen cross-linking, also known as CXL or C3R, is a treatment used to treat progressive (worsening) keratoconus. The aim of this treatment is to stop things getting worse, although, for some people cross-linking can also cause an improvement.
It is thought that CXL works by increasing the number of naturally occurring collagen cross-links in your cornea, making it stronger. Treatment can be carried out by an ophthalmologist or sometimes nurse specialist and involves removing a small area of the surface of your cornea, known as the epithelium, and then applying vitamin B2 (riboflavin) drops. Your cornea is then exposed to ultraviolet-A (UVA) light.
Cross-linking treatments take around 30-60 minutes and you do not need to stay in hospital overnight. You would normally be awake for the procedure.
The main aim of CXL is to stop keratoconus getting worse, preventing your vision from deteriorating in the future. Cross-linking is usually carried out on one eye at a time, and may need to be repeated.
There is some promising evidence that CXL is very successful in stopping the development of keratoconus and more evidence is being collected all the time, to help CXL become a regular treatment.
Most people with keratoconus are able to get good vision with contact lenses. But, if wearing contact lenses becomes very uncomfortable and you can only wear them for very short amounts of time, or your corneas are scarred and you can’t get much improvement of your sight with contact lenses, your ophthalmologist may suggest that you have a corneal transplant.
A corneal transplant is surgery to remove all or part of a damaged cornea and replace it with healthy, clear cornea tissue from the eye of a donor who has died. It is possible to carry out transplants which replace all, or only some layers of your cornea, with healthy donor tissue.
Only about 10-25 per cent of people with keratoconus need to have a corneal transplant. More information on transplants is available on the corneal transplant page
Complications of Keratoconus
Corneal hydrops is a rare complication of keratoconus. It occurs when fluid from inside your eye enters your cornea through breaks in the membrane at the back of the cornea. This fluid causes the cornea to become swollen.
This swelling can affect your vision, making it blurry, even with your contact lenses in. It can also give your cornea a cloudy or milky appearance. Hydrops can cause irritation or pain, light sensitivity and make your eye watery (teary) and red.
The breaks in your cornea will usually take at least three months to heal. You will usually be advised not to wear contact lenses while your eye is recovering. If you feel any discomfort or pain, your ophthalmologist can give you eye drops to make your eye feel more comfortable.