Keratoconus Part 1 – what is it?

Keratoconus is an eye condition that is often diagnosed in puberty or early adult years. It often affects both eyes, however one eye may have more advanced keratoconus. It occurs in about 1 in 2000 people, however better diagnostic techniques have suggested it may occur as frequently as 1 in 500 people. (1)

Keratoconus affects the front surface of the eye. The clear dome at the front of the eye termed the ‘cornea’ becomes thin and changes shape in keratoconus. Generally, this condition progresses in our teenage years to early adult years, causing vision blur.

The altered shape of the cornea in keratoconus may often mean there is a limit to the vision achieved in spectacles. The distorted front layer of the eye affects light rays from focusing through to the back of the eye, which is why specialised contact lenses often provide clearer vision. The smooth, regular shape of the contact lens allows for light to focus properly in the eye, and thus provides clearer vision.

It is important to keep in mind that there are different levels of severity for keratoconus, and this determines the affect keratoconus has on your vision and the best tool/s to help you see clearly. For the
safety of your eyes, it is especially important to ensure that  keratoconus is monitored appropriately with an optometrist experienced in managing this condition. Keratoconus does not cause blindness, however can lead to low levels of vision if not managed or treated appropriately. Fortunately, we have successful treatments (surgical and non-surgical) that can ensure you have good vision to minimise its impact on your daily tasks.

What causes keratoconus?

The exact cause of keratoconus is unknown, however research has identified multiple risk factors. Current research has shown environmental, behavioural (such as eye rubbing) and multiple genes contribute to keratoconus. (2) In some individuals keratoconus is suggested to be entirely associated with eye rubbing and atopy (allergies, hayfever, eczema, asthma) which is why avoiding eye rubbing and managing itchy/irritated eyes is very important. (3)

In other individuals, keratoconus is suggested to be primarily a result of particular genes inherited. (3) Population studies have showed variable rates in different ethnicities. Research has identified higher incidence in Asians than Caucasians and suggested higher incidence and more aggressive keratoconus in Maori and Polynesian populations in New Zealand. (4,5) Due to genetic risk factors, it is very important that if you or one of your family members have keratoconus you inform your optometrist. All family members should be checked for this condition, especially children, adolescents and young adults.

Genetic conditions that are associated with keratoconus include Ehlers-Danlos Syndrome, Marfan’s Syndrome and Down’s Syndrome (Trysomy 21). (6)

How is keratoconus diagnosed?

Frequent spectacle changes or unclear vision with haloes/flaring in spectacles can often raise suspicion for keratoconus. There are multiple technologies that we use to assess for keratoconus and some of these may not be available in all practices. Priority technology for diagnosis of keratoconus include corneal topography and/or tomography, where a map is taken to assess the shape of the front of the eye (see image on the right), in addition to measurement of corneal thickness and slit lamp microscope examination.

KC Topography

What treatment options are available?

It is important to minimise risks for further keratoconus progression. It is strongly suggested to ensure no eye rubbing and to manage any eye allergies so that there is no temptation to rub the eyes.

There is a surgical treatment that eye surgeons can also offer to slow and in some cases halt keratoconus progression when there is documented keratoconus progression (see corneal crosslinking in Keratoconus Blog 2).

There are multiple options for correcting vision – from spectacles in mild keratoconus to different contact lens technologies, in addition to surgical options.

 References
1 https://www.keratoconus.org.au/about-kc/
2 Abu-Amero KK, Al-Muammar AM, Kondkar AA. Genetics of keratoconus: where do we stand?. J Ophthalmol. 2014;2014:641708.
3 Rabinowitz YS. Keratoconus. Survey of Ophthalmology. 1998;42(4):297–319.
4 Weed KH, MacEwen CJ, Giles T, Low J, McGhee CNJ. The Dundee University Scottish Keratoconus study: demographics, corneal signs, associated diseases, and eye rubbing. Eye. 2008;22(4):534–541.
5 Owens H, Gamble GD, Bjornholdt MC, Boyce NK, Keung L. Topographic indications of emerging keratoconus in teenage New Zealanders. Cornea. 2007;26(3):312–318.
6 Abu-Amero KK, Al-Muammar AM, Kondkar AA. Genetics of keratoconus: where do we stand?. J Ophthalmol. 2014;2014:641708.
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About Natalie

Natalie Buckman is a clinical optometrist, educator,  professional leader and ophthalmic medicines prescriber, who enjoys exploring the world and hitting the dance floor in her spare time.