What is Keratoconus?
Keratoconus is a progressive condition in which the transparent ‘front window’ of the eye, the cornea, thins and begins to bulge into a cone-like shape. This irregular cone shape deflects light as it enters the eye, causing distorted vision. Although no one can be sure how far keratoconus will develop in an individual, the condition does not cause blindness. With the current treatments available, most people should be able to lead a normal life despite this condition. However, good vision may be difficult to maintain at times and contact lens tolerance varies.
Causes, incidence, and risk factors
The cause is unknown but it could have a genetic component and some researchers believe that allergy and eye rubbing may play a role. Keratoconus is thought to involve a collagen defect in the corneal stroma, the main structure of the corneal tissue allowing the cornea to stretch and thin.
The incidence of keratoconus in the general population is reported to be about 1 in 2000 but mild cases occur up to ten times more often. It rarely appears in an individual until puberty and often begins during a person’s teens or early 20s.Keratoconus can occur in one or both eyes and sometimes one eye may be badly affected while the other eye may show very little sign of the condition.
The earliest symptom is subtle blurring of vision even with glasses and frequent changes in prescription with increasing short sight and astigmatism. Some patients report increased glare when driving at night or in sunshine. In advanced cases ‘hydrops’ can occur: this is the sudden onset of discomfort, redness and reduced vision caused by a split in the inside of the cornea. It usually clears after a few weeks but may leave permanent scarring.
Signs and tests
The corneal distortion may be seen with a slit lamp microscope. Retinoscopes and keratometers are used to measure eyes for glasses and contact lenses: in keratoconus they show abnormal readings. One of the most accurate tests we carry out is called corneal topography, which creates a map of the corneal surface and accurately diagnoses and measures the keratoconic changes. When keratoconus is advanced, the cornea will be thinner at the point of the cone.
Contact lenses are the main treatment option for most patients with keratoconus. We fit a wide range of specialist lenses to give patients optimum vision and comfort .Gas permeable (rigid) contact lenses are usually needed but sometimes special types of soft lenses work well. Normal vision is restored to all except advanced cases. Lifelong wear is necessary although tolerance can vary.
Severe cases may require surgical intervention e.g. corneal/partial corneal graft as a last resort.
Newer technologies may delay or prevent the need for corneal graft e.g. collagen cross- linking, Intacs implants.
If you would like to discuss keratoconus and the treatment options please contact us.