The cornea is a very important part of your eye. Light enters the eye through the cornea, which refracts, or focuses, the light rays for clear vision. With keratoconus, the shape of the cornea is altered, distorting vision. Keratoconus can make some activities difficult, such as driving, typing on a computer, watching television, or reading.
Keratoconus is an uncommon condition in which the normally round, dome-like cornea (the clear front window of the eye) becomes thin and develops a cone-like bulge. Keratoconus literally means "cone-shaped cornea." With keratoconus, the shape of the cornea is altered, distorting your vision. Keratoconus can make some activities difficult, such as driving, typing on a computer, watching television or reading. The cause of keratoconus is still not known. Some researchers believe that genetics play a role, since an estimated 10 percent of people with keratoconus also have a family member with the condition.
Keratoconus is sometimes associated with:
- An eye injury, i.e., excessive eye rubbing or wearing hard contact lenses for many years
- Certain eye diseases, such as retinitis pigmentosa, retinopathy of prematurity, and vernal keratoconjunctivitis
- Systemic diseases, such as Leber's congenital amaurosis, Ehlers-Danlos syndrome, Down syndrome, and osteogenesis imperfecta
Keratoconus usually affects both eyes, though symptoms in each eye may differ. Symptoms usually start to occur in people who are in their late teens and early twenties. Keratoconus can be detected through a routine eye exam although additional tests may be indicated to determine the shape of your cornea. The rate of progression varies. Keratoconus will often progress slowly for 10 to 20 years and then suddenly stop. As the condition progresses, most common symptoms include:
- Increased sensitivity to light
- Mild eye irritation
- Increased blurring and distortion of your vision
- Increased nearsightedness or astigmatism
- Frequent eyeglass prescription changes
- Inability to wear contact lenses
Keratoconus treatment often depends on the severity of the kerataconus symptoms. During early stages, vision can be corrected with eyeglasses. As the condition progresses, rigid contacts may need to be worn so that light entering the eye is refracted evenly and vision is not distorted. Rubbing the eyes can aggravate the thin corneal tissue and make symptoms worse.
Occasionally, keratoconus can advance rapidly, causing the cornea to become scarred. Scar tissue on the cornea causes the cornea to lose its smoothness and clarity. As a result, even more distortion and blurring of vision can occur, in these extreme cases a corneal transplant procedure may be indicated when good vision is no longer possible with contact lenses. This surgery is only necessary in about 10 percent to 20 percent of patients with keratoconus. In a corneal transplant, the surgeon removes the diseased cornea from the eye and replaces it with a healthy donor cornea.