What is keratoconus
Keratoconus is a disease of the cornea, or front surface of your eye.
Most people who are diagnosed with keratoconus have never even heard of it. They often assume the worst – that because it usually gets worse over time, therefore they will probably go blind. However, this is not the case if it is managed and treated properly from the start.
Keratoconus is a disease of the cornea, or front surface of your eye. The incidence in Australia is about 1 in 2,000 (so there are at least 10,000 Australians with the condition). It usually appears around puberty and progresses (gets worse) during your teens and twenties.
During the progressive phase of the eye disease, your cornea becomes thinner and weaker and the surface becomes irregular or conical in shape. Your vision becomes more and more affected depending on the position and size of the conical shape. Sometimes keratoconus is also called conical cornea.
What is forme fruste keratoconus?
This is when the disease starts in your eye but then stops getting worse for some reason. This may happen before it even causes noticeable problems with your vision. It is a very mild form and not usually picked up unless you have tests for laser eye surgery. Learn more about forme fruste keratoconus.
Getting the right diagnosis
Your keratoconus may be worse in one eye than the other – sometimes much more so.
This explains why a wrong diagnosis sometimes occurs.
If your practitioner doesn’t see keratoconus often, they may explain the poor vision in one eye as amblyopia (or lazy eye). It is only when the vision in the other eye starts to deteriorate that they might look more closely and discover the real cause.
We are aware of many patients that have been diagnosed later in life but originally have been mistaken as having a lazy eye. They have then been allowed to go through life with no binocular vision and all the associated issues that can occur.
Today this should never happen as we have at our disposal, highly sensitive measuring technology, but also an effective procedure called collagen cross-linking that can nip keratoconus in the bud.
This makes it more important than ever to diagnose the keratoconus patient as early as possible. This procedure uses riboflavin and UV light to stop progression or at least slow it down significantly.
It is especially important if the patient is under the age of 25 years of age, when progression is most likely. Diagnosis of moderate-to-severe disease is relatively simple – especially if the condition is affecting the vision in both eyes. Milder cases can be more difficult to pick up.
What Eye Tests do you need?
There are many instruments that your keratoconus expert will use to diagnose and track your disease, depending on their practice and how often they see this disease.
Corneal Topography (corneal shape)
A corneal topographer (such as a Medmont or Orbscan) measures and maps the exact shape of your eye. It produces a scan like the one here. This is the single most important tool your optometrist will have in diagnosing keratoconus.
It also accurately monitors your eyes to see if they are getting worse over time. This is called progression of the disease.
The topographer also helps with choosing the best possible contact lens for your eye.
A scan of your cornea will instantly show the characteristic hallmark appearance of keratoconus (see image).
Global Pachymetry (Corneal thickness)
Keratoconus is firstly a progressive corneal thinning. Being able to measure how thick the cornea is becomes critical in monitoring progression.
The eye condition can be picked up even earlier through repeated corneal thickness measurements, which show subtle corneal thinning before any shape-change occurs.
This test is called global pachymetry using an instrument called an Optical Coherence Tomographer.
A Pentacam can also be used to provide similar information about your eyes.