What is Keratoconus?
Keratoconus is an eye condition where the clear, dome shaped cornea at the front of the eye gradually starts to thin, weaken, and eventually bulge outwards into a cone shape.
The change in corneal shape alters the way that light enters the eye, causing blurring and distortion of vision, which progressively worsens with time. Due to the slow progressive changes, it may not require treatment initially, but rather regular monitoring for changes in vision and disease progression, at which point there are a variety of treatment options available.
Doctors are unclear of the exact cause of keratoconus, but it is thought to be due to a mixture of environmental and genetic factors. The American Academy of Ophthalmology suggest that 1 in 10 people diagnosed with keratoconus have a parent with the same condition.1
It can also be associated with excess eye rubbing, allergic conditions such as asthma and eczema and some connective tissue disorders. It is more common in non-Caucasians.
When and how is it diagnosed?
It is often picked up in the community by an optometrist during a routine eye examination. Symptoms can start in early to late adolescence and gradually worsen over 10-20 years.
The earlier it is picked up the better, as monitoring can be commenced, visual correction offered, and intervention considered.
What symptoms can you present with?
Early symptoms may include blurring of vision, eye strain and headaches, distortion of straight lines, or monocular double vision (due to one eye being more affected than the other). The changes in the cornea affect the way that the eye can focus so patients may develop myopia (short sightedness) and astigmatism (blurred vision at near and far distance).
What are the treatment options?
Initially, in the early stages of Keratoconus patients may just require glasses to correct their vision. For some patients the disease may not progress further than mild symptoms.
For other patients, as the disease progresses, they may go on to need special contact lenses, designed for the altered shape of their cornea, that help correct visual defects. These may initially be soft contact lenses, but as the cornea changes more rigid “hard” lenses are required.
Some patients with mild to moderate keratoconus may be offered a Perspex corneal ring implant (Kerraring TM). This does not stop progression but helps improve quality of vision by reshaping and strengthening t
he cornea.
In some severe cases patients may need to undergo a corneal transplant, a surgical procedure where the diseased cornea is removed and replaced by a donor cornea.
However, a newer treatment, called Corneal collagen cross linking, can help prevent disease progression by using UV light and vitamin B12 (riboflavin)to strengthen the cornea. It is suitable for use in certain patients with active disease progression and is effective in over 94% of patients. This has helped reduce the need for corneal transplant.
Keratoconus and cataracts
As a cataract surgeon I meet people with all sorts of corneas. It may seem surprising, but it is not infrequently that I come across a patient requiring cataract surgery who has undiagnosed keratoconus.
This presents a challenge as choosing the correct type and power of intraocular lens to be inserted into your eye can be more difficult. There is a higher risk of refractive surprise, this simply means a larger than expected need for glasses or contact lenses post-surgery. Cataract surgery does not eliminate the need for glasses for either distance or near focus in most keratoconus patients. Spectacles, or more likely contact lenses, will still be needed post-operatively.
Take home message
If we can diagnose keratoconus early, we can really make a difference to vision in early and later life, and even prevent corneal graft surgery. So please make that appointment for yourself or your child for a general eye exam with your local optometrist.
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