Keratoconus is a condition that results in progressive thinning and weakening of the cornea. This results in the change in shape of the cornea leading to astigmatism and blurred vision. As the name suggests the cornea can become cone shaped resulting in irregular astigmatism (type of astigmatism that cannot be readily corrected with spectacles). It often presents in the late teens or early twenties and can be more common in individuals of South Asian heritage.
In most cases there is no specific cause, but it is thought to have a genetic component as well as being associated with eye rubbing and allergies and eczema. It is more common in people with Trisomy 21 (Down’s Syndrome). It is often progressive but generally slows down as we get in to our 30s.
There are no treatments that can cure or reverse the condition, but a treatment know as cross-linking can slow down the disease and make it easier to improve the vision.
Corneal Crosslinking (CXL)
This treatment involves removing the surface cells of the cornea and administering Riboflavin as drops to the cornea and then shining Ultraviolet light to cause a reaction that results in crosslinking (strengthening) of the collagen within the cornea. This prevents further bulging of the cornea thus halting the disease progression. Dr Tint offers the latest epi-off accelerated crosslinking using the Avedro system.
Spectacles and contact lenses whether soft or hard will help improve the vision. Contact lenses will always result in better vision than spectacles.
Moderate and Advanced Cases
Spectacles become less helpful as the condition progresses. However, Rigid Gas Permeable Contact Lenses (RGPCLs) will be more successful. If the condition progresses, then the shape of the cornea becomes unsuitable for Contact lenses and alternatives must be sought.
1. Intrastromal Corneal Rings
These are small plastic segments that are placed within the cornea to help improve the shape whereby spectacles become more effective or CLs start to fit better. Moreover, it can also improve vision without any spectacles and Contact lenses however, these are not designed to permit freedom from spectacles or Contact lenses.
2. Topography Guided Laser Eye Surgery
Although laser eye surgery should, in general, not be performed in patients with keratoconus, a very specialised treatment whereby laser is used to sculpt the surface into a more favourable shape. This can improve the quality of vision but is not designed to remove the need for spectacles or Contact lenses. This treatment will need to be combined with crosslinking.
3. Implantable Lenses
These implantable contact lenses are placed inside the eye behind the iris but in front of the natural lens. These can be used to reduce spectacles prescription and can often be used in conjunction with intrastromal corneal rings. This option is more suited to patients under the age of 40.
4. Lens Surgery
This is where the natural lens is surgically removed in exactly the same way as for cataracts then it is replaced by a clear artificial lens which allows the reduction of the prescription. Again, this can be done in conjunction with intrastromal corneal rings. Lens surgery is more suitable for people over the age of 40 or have the beginnings of a cataract.
5. Corneal Transplantation
This option is only considered if other less invasive options have been explored and are deemed unsuitable. Ideally, it is best to aim to perform a big bubble deep anterior lamellar keratoplasty (DALK) as this technique preserves the patients own corneal back layer of cells therefore there cannot be rejection of this very important layer. However, DALK using the big bubble technique can be technically challenging with 70% of attempts being successful. Failing this a full thickness or penetrating keratoplasty can be performed. Having this procedure does not mean it is second best or a failure. It remains an excellent option with very good long term results.