For people with Keratoconus contact lenses are often the best way to achieve vision correction. There are many different types of lenses and this article looks at the limitations of Hydrogel lenses for Keratoconus.
Keratoconus is a disease of the eye. The cornea, which is the front part of the eye, thins and becomes misshapen leading to the front of the eye developing an irregular ‘cone’ shape.
This bulging effect results in distortion of the light entering the eye causing blurring and ghosting of images.
While spectacles may produce some correction for early, or very mild, cases of Keratoconus, once the condition progresses beyond a certain point it becomes impossible to get reasonable correction with spectacles.
Contact lenses are often the next form of correction used, however there are many different types of contact lenses and some of them are more effective than others.
Hydrogel lenses are what are sometimes called ‘soft’ contact lenses.
Traditional Hydrogel lenses are very soft and flimsy and as such they fit very closely to the cornea of the eye.
This has the advantage of making them very comfortable to wear and this is, of course, one of the reasons they have become the most popular kind of lenses for normal vision correction.
However, this close fit makes them of very limited use in the treatment of Keratoconus.
Because they fit very closely, they form the same shape as the cornea. As it is this very shape of the cornea that is the basic cause of vision problems in someone with Keratoconus, the correction offered by these very soft and thin lenses is minimal.
If you imagine that a normal eye is rounded like a soccer ball and an eye with Keratoconus is shaped more like the end of a rugby ball. In order to correct vision the shape at the front of the eye needs to be made as close to the normal shape as possible.
A traditional Hydrogel lens is like laying a cloth over the end of the rugby ball. It moulds to the contours and the light coming into the eye is still distorted.
In the last few years there have been some advances in contact lens material technology. New materials have allowed the creation of contact lenses that are slightly thicker than traditional hydrogel lenses.
Although they retain much of the comfort of soft lenses they have more of a tendency to hold their own shape rather than just draping over the surface of the eye.
This means that they can be more effective for some cases of Keratoconus than has previously been possible with hydrogels. Having said that they are still of limited effect if the condition becomes more severe.
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Find out more about Keratoconus, treatments and living with the condition at WHAT IS KERATOCONUS!