Sometimes the front part of the eye called the cornea which is normally round becomes thin and irregularly- or cone-shaped. This abnormal shape prevents the light entering the eye from being focused correctly on the retina and causes distortion of vision; a disorder called Keratonconus. 

 

In its earliest stages, usually in a person’s late teens or late twenties, keratoconus causes slight blurring and distortion of vision and increased sensitivity to glare and light. It may progress for 10-20 years, with each eye affected differently, and then slow in its progression. Although there are no medicines that can prevent the disorder from progressing, there are several things that an optometrist can do. 

 

In the early stages of Keratonconus mild nearsightedness and astigmatism can be caused, in which case eyeglasses or soft contact lenses may be used for correction.   As the disorder progresses and cornea continues to thin and change shape, carefully-fitted, rigid gas permeable contact lenses can be prescribed to correct vision. In most cases, this is adequate and all that is needed are frequent checkups and lens changes to achieve and maintain good vision.  

 

Sometimes the cornea bulges more and vision may become more distorted. In a small number of cases, the cornea will swell when the strain of the protruding cone-like shape causes a tiny crack to develop and will cause a sudden and significant decrease in vision. The swelling may last for weeks or months as the crack heals and is gradually replaced by scar tissue. If this occurs an optometrist can prescribe eyedrops for temporary relief from the swelling. In a few cases, a corneal transplant is necessary. However, even after a corneal transplant, eyeglasses or contact lenses are often still needed to correct vision.