The cornea is the transparent dome-shaped window on the surface of the eye, overlying the coloured iris. Its smooth round surface is important for maintaining clear vision. In keratoconus the cornea becomes thin and distorted, eventually protruding forwards in a cone-like shape. It typically affects both eyes, but can often be quite asymmetric.
The causes of keratoconus are not very well understood. However there is a genetic tendency, so it can sometimes run in families. There is also an association with allergies and most people with keratoconus have itchy eyes and rub their eyes to some degree. Over several years the pressure on the eye from rubbing may contribute to distortion of the cornea.
Keratoconus occurs in young people, often starting in the teens, or even younger. It usually progresses slowly, and then stabilizes in the thirties or forties. It affects males and females in all racial groups, although in New Zealand it is most common in the Maori and Pacific populations.
Keratoconus causes blurring and distortion of vision in one or both eyes. It often gets slowly worse over time, but occasionally causes quite a sudden deterioration in vision. People with keratoconus often have associated allergic conjunctivitis, which causes itchy eyes and eye rubbing.
Corneal collagen cross linking (CXL) is an effective new treatment for keratoconus and other forms of corneal ectasia. A combination of ultraviolet light and vitamin B2 causes corneal collagen fibres to bond more tightly to each other. This stiffens the cornea, making it less prone to deformation and slows or halts the progression of corneal ectasia.
Keratoconus can cause significant loss of vision. By stabilising the cornea in the early or moderate stages of the disease, further vision loss can be prevented. About 50% of people also have some improvement, with flattening of the cornea, better unaided and corrected vision and improved contact lens tolerance. CXL also reduces the need for corneal transplant surgery, by preventing keratoconus from progressing to more advanced disease.
Collagen cross linking is suitable for adults and teenagers with mild or moderate keratoconus that has shown definite progression over a period of at least 3 months. This includes at least 1 dioptre of corneal steepening or refractive change. A clear cornea with a minimum thickness of 400 microns is required.
CXL is performed by Dr Penny McAllum in the Eye Doctors clinic at Ormiston Hospital and Ascot Hospital. One eye of a patient is treated at a time. After local anaesthetic eyedrops are instilled, the central corneal epithelium is removed and the surface of the eye is soaked in Riboflavin (Vitamin B2) eyedrops for half an hour. The cornea is then exposed to a specially calibrated ultraviolet light for half an hour, with regular checks to ensure the cornea is not becoming too thin. A bandage contact lens is placed and left on for several days while the eye heals. Antibiotic and anti-inflammatory eyedrops are used for up to 4 weeks and painkillers are prescribed for use as necessary in the first 2-3 days. About 5 follow-up visits are required in the 3 months following the treatment.
Southern Cross Affiliated provider benefit to Keratoconus Patients
- no need for prior approval
- Southern Cross pays Eye Doctors directly