Keratoconus – what is it?
Keratoconus is a disease of the cornea (the curved, clear window at the front of the eye) that is often visually debilitating. In keratoconus there is a thinning of the cornea, and as a result, the cornea develops a cone-like bulge and becomes distorted. The distorted cornea affects the focusing ability of the eye, impairing the vision.
Keratoconus is estimated to occur in 1 out of every 2000 persons, both men and women. The onset of Keratoconus can be anywhere between the ages of 8 and 45. In the majority of cases, it becomes apparent between the ages of 16 and 30 years. Keratoconus generally affects both eyes although one eye may be significantly more affected.
Keratoconus does not cause total blindness. If left untreated, keratoconus can however lead to significant vision impairment, and can result in legal blindness.
New research suggests the weakening of the corneal tissue that leads to keratoconus may be due to an imbalance of enzymes within the cornea. This imbalance makes the cornea more susceptible to oxidative damage from compounds called free radicals, causing it to weaken and bulge forward.
What are the risk factors?
Risk factors for oxidative damage and weakening of the cornea include a genetic predisposition, explaining why keratoconus often affects more than one member of the same family.
Keratoconus is also associated with overexposure to ultraviolet rays from the sun, allergies, excessive eye rubbing, a history of poorly fitted contact lenses and chronic eye irritation.
What are the signs and symptoms?
- Blurring and distortion of vision that may be corrected with spectacles in the early stages of the condition. Once the condition has progressed it is often difficult to satisfactorily correct the vision with glasses and your optometrist may need to fit a more rigid or hard contact lens.
- Irregular astigmatism (irregular curvature of the cornea)
- Short-sightedness (myopia)
- Frequent changes to the spectacle prescription
- Light sensitivity
How is keratoconus detected?
Identifying moderate or advanced keratoconus is fairly easy. However, diagnosing keratoconus in its early stages is more difficult, requiring a search for visual and refractive clues and the use of instrumentation (topographer) during the eye examination with your optometrist. Often, keratoconus patients have had several spectacle prescriptions in a short period, and none has provided satisfactory vision correction. Prescriptions are often variable and inconsistent. Keratoconus patients often complain of distortion rather than blur at both distance and near vision. Some report halos around lights and extreme light sensitivity or photophobia.
What treatments are available for keratoconus?
When seeking treatment for keratoconus it is very important to see an optometrist who is experienced in managing keratoconus. As contact lenses are often the best form of vision correction in keratoconus, it is essential to see an optometrist who specialises in contact lens fittings.
Most people with keratoconus are under the impression that the only form of treatment available is corneal transplantation. There are many treatment options available and only in certain cases is transplantation required. In fact up to 95% of keratoconus can be managed very well with glasses and or speciality contact lenses.
There has also been the introduction of two forms of therapy, which have been proven to slow the progression of advancing keratoconus. Intacts and corneal cross-linking therapy are now offered by ophthalmologists specialising in the cornea. Your optometrist will give you advice on the most appropriate treatment at your eye consultation.
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