Keratoconus (ker-uh-toe-KOH-nus) occurs when your cornea — the clear, dome-shaped front surface of your eye — thins and gradually bulges outward into a cone shape.

A cone-shaped cornea causes blurred vision and may cause sensitivity to light and glare. Keratoconus usually affects both eyes and generally occurs in people ages 10 to 25. The condition may progress slowly for 10 years or longer.

Vision problems can be corrected with glasses or soft contact lenses early on in the condition. As keratoconus progresses, you may have to be fitted with rigid gas permeable contact lenses or other types of contact lenses. Advanced keratoconus may require a cornea transplant.

Symptoms Causes Risk factors Complications

Signs and symptoms of keratoconus may change as the disease progresses. They include:

  • Blurred or distorted vision
  • Increased sensitivity to bright light and glare
  • Problems with night vision
  • Many changes in eyeglass prescriptions
  • Sudden worsening or clouding of vision, caused by a condition in which the back of your cornea ruptures and fills with fluid (hydrops)

When to see a doctor

See your eye doctor (ophthalmologist or optometrist) if you have irregular curvature of the eye (astigmatism) and your eyesight is worsening rapidly. Your eye doctor also may look for signs of keratoconus during routine eye exams.

If you're considering laser-assisted in-situ keratomileusis (LASIK) eye surgery, make sure your doctor checks for signs of keratoconus before you proceed.

The cause of keratoconus is unknown.

Keratoconus may be associated with:

  • Vigorous rubbing of your eyes
  • Other eye conditions, including retinitis pigmentosa, retinopathy of prematurity or vernal keratoconjunctivitis
  • A combination of several disorders, such as enzyme abnormalities or hereditary factors including Down syndrome
  • Wearing contact lenses for several years

These factors can increase your chances of developing keratoconus:

  • Certain diseases. The risk of developing keratoconus may be higher if you have certain inherited diseases or genetic conditions, such as Down syndrome, Leber's congenital amaurosis, Ehlers-Danlos syndrome or osteogenesis imperfecta.
  • Family history of keratoconus. If you have a family history of keratoconus, you may have a higher chance of developing keratoconus.

In some situations, your cornea may swell quickly and cause sudden reduced vision and scarring of the cornea.

In advanced keratoconus, your cornea may become scarred, particularly where the cone forms. A scarred cornea causes worsening vision problems and may require corneal transplant surgery.

The effect of ongoing vision problems on your daily life also can lead to anxiety. However, finding ways to adapt to your condition can lessen anxiety.

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