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I started to see blurry and the optometrist told me I am beginning to get something called keratoconus. What is this?

Keratoconus is a condition affecting the cornea, which is the clear dome shaped-structure at the front of the eye, over the iris, the coloured part. Guyanese sometimes call the cornea the ‘baby’ of the eye.

Ordinarily, the cornea is shaped like a semi-circle, like half of a tennis ball. In keratoconus, the centre of the domed or semi-circular shape of the cornea becomes thinner and bulges out and appears pointed, or cone shaped. The cornea is one of the surfaces that is used to focus light on the retina, which allows us to see clearly.

As you can imagine, if this surface becomes irregular, the image you see becomes distorted. As the cornea becomes steeper, it refracts the light more, and so you become more nearsighted.

As it changes shape and becomes more irregular, you get more astigmatism. One of the main clues in diagnosing keratoconus is a sudden increase in astigmatism. In the early stages, the vision may still be correctable to 20/20 with glasses, but in the later stages, you get better vision with special contact lenses.

Why did I get this?

The exact cause of keratoconus has not been found, but in some patients, there is a family history of the condition.. It affects men and women almost equally, and is usually bilateral, ie, affecting both eyes, although one eye may be more affected than the other. It tends to start in the teenage years. Patients who previously had good vision, suddenly notice that it is not as clear as before, and the images look a little distorted. The optometrist can determine if it is just near sightedness and/or astigmatism or if it is keratoconus by a thorough eye examination.

Optometrists use a specialized instrument called a keratometer to measure the curvature of the cornea. In patients with normal corneas, this instrument gives a clear image on the cornea, but in patients with keratoconus, this image is distorted. As well, the curvature of the cornea is much steeper in patients with this condition.

Can it be treated?

In the early stages, the vision can be usually corrected by glasses. Some people have the cone inferior (below) the pupil and they have better vision that those people whose cone is more central.

As the condition progresses, and the cornea becomes more steep, you can usually get better vision with the use of gas permeable (GP) contact lenses. A GP lens is made of a rigid material, like hard plastic, as opposed to soft lenses which are very flexible, like soft plastic.

The reason a rigid lens must be used, is so that it can hold its shape, as a soft lens would simply mould to the existing shape and thus not allow complete correction of the problem.

Keratoconus lenses are specially made to fit the irregular shape of the cornea. Some of them are made with the back curve made steeper to match the steep cornea and the front curve spherical (similar to the normal cornea). There are several specialized designs of lenses available, and the fitter may need to try several before they can get a good fit that is comfortable.

Will it get worse? Can I go blind?

Most people can achieve good vision with glasses or contact lenses. In some patients, if the shape of the cornea becomes too irregular for contact lens fit, or if scarring of the cone portion occurs, then a corneal transplant is needed.

The ophthalmologist replaces the diseased portion of the cornea with a donor button. Corneal transplants are very successful, with success rates higher than 90per cent, and so it is rare for a person with keratoconus to become severely visually disabled.