What is Keratoconus?
Keratoconus is a condition affecting the cornea, the clear part at the front of the eye, which causes it to become softer and thinner than those of normal corneas.
Under the influence of the internal eye pressure, the cornea then changes shape. As the cornea is the main part of the eye that focuses light, this shape change distorts the image that forms on the retina, at the back of the eye, even if you are wearing glasses.
Keratoconus can start as early as 9 years of age but is usually diagnosed in the early 20s. It can be active for up to 10 years, after which it tends to stabilise.
What Causes Keratoconus?
There is no one single cause of keratoconus. Current theories suggest that genetics, the environment and the endocrine system all contribute to the condition.
Eye Rubbing
Some studies have suggested that mechanical trauma, such as eye rubbing, can contribute to the acceleration of keratoconus.
Allergies
A higher proportion of people with keratoconus have allergies or atopic conditions such asthma and eczema. It is yet unclear how these conditions relate to keratoconus itself.
Oxidative Stress/Free Radicals
Some studies indicate that, in keratoconus, the cornea processes superoxide radicals abnormally. As it cannot eliminate free radicals (normal by-products of cell metabolism) properly, this can lead to damage to the collagen fibres in the cornea.
Hormonal
Keratoconus tends to become active at puberty and can progress during pregnancy; therefore it is hypothesised that the endocrine system may be involved. However, this theory is still considered controversial.
Symptoms of Keratoconus
The early symptoms of keratoconus include blurred vision that cannot be corrected by spectacles, frequent changes in spectacle prescription and rapid increase in astigmatism at a time when the eyesight should have stabilised.
The following are all symptoms of keratoconus but it should also be noted they can also occur in other conditions as well. You should always consult an eye care professional if you are concerned about your vision.
- Increased light sensitivity
- Difficulty driving at night
- Haloes and ghosting, especially at night
- Eye strain
- Headaches and general eye pain
- Eye irritation, excessive eye rubbing
Diagnosis of Keratoconus
Once keratoconus is fairly well established, there are physical signs that can be detected by your eye care professional using a slit lamp bio microscope. Below are some of the signs.
- Corneal thinning
- Fleischer’s ring (an iron coloured ring surrounding the cone)
- Vogt’s striae (stress lines caused by corneal thinning)
- Corneal scarring
However, early cases are best detected using Topography which is a method of mapping the corneal shape. Most topography machine software includes the ability to detect keratoconus based on the typical shape changes of the condition.
Management of Keratoconus
Contact lenses are used to restore a better corneal shape and focus. Most people with keratoconus have to rely on contact lenses to regain functional vision. Up until recently it was the only way to manage the condition.
In early cases, normal disposable contact lenses can work well, especially in cases where the thinnest part of the cornea is not directly in the line of sight.
As the condition progresses, the cornea becomes more distorted and more specialist contact lenses are needed to restore clear vision.
Traditionally, rigid contact lenses were used to improve vision in keratoconus. Although they can give good vision, in some cases, they can prove to be uncomfortable to wear for long periods of time.
Now, specialist soft lenses, such as the KeraSoft IC, are proving to be highly successful in not only providing clear vision but also all day comfortable wear. This has been a breakthrough in improving quality of life for people with keratoconus.
Treatment for Keratoconus
Traditionally, the only way of managing keratoconus was to provide contact lenses or perform a corneal graft.
In the 1990’s, a procedure called Corneal Collagen Cross Linking (CXL) was developed. This procedure causes strengthening and stiffening of the collagen fibres within the cornea which acts to slow or completely stop further progression of the condition.
This procedure does not cure the condition as contact lenses and spectacles will still be required afterwards.