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, though it often affects one eye more than the other. It generally begins to affect people between the ages of 10 and 25. The condition may progress slowly for 10 years or longer.

In the early stages of keratoconus, you might be able to correct vision problems with glasses or soft contact lenses. Later, you may have to be fitted with rigid, gas permeable contact lenses or other types of lenses, such as scleral lenses. If your condition progresses to an advanced stage, you may need a cornea transplant.

A new treatment called corneal collagen cross-linking may help to slow or stop keratoconus from progressing, possibly preventing the need for a future cornea transplant. This treatment may be offered in addition to the vision correction options above.

Source: https://www.mayoclinic.org/diseases-conditions/keratoconus/symptoms-causes/syc-20351352

Keratoconus changes the vision of two ways:

  • The smooth surface over the eye becomes wavy as the cornea changes shape. This is known as an irregular astigmatism.
  • Vision becomes more nearsighted as the front of the cornea is expanded and anything too far will be blurry.

Symptoms for keratoconus include the following:

  • Sudden change of vision in one eye
  • Double vision or “ghost images”
  • Distorted vision, with objects both near and far
  • Lights with halos or streaks
  • Blurred vision while driving

Keratoconus usually begins in adolescence and seems to run in families. The disease progresses more rapidly in people with certain medical problems, most commonly in people with allergies or other conditions that lead to chronic eye rubbing.

The cornea can change shape relatively quickly or may occur over several years. These changes can lead to blurred vision or a constant glare. Changes can also stop quickly or continue for decades. There is no way to predict how the condition will progress. In most cases, both eyes are eventually affected, although not always to the same extent.

Treatment usually starts with new glasses. If the lenses do not provide adequate vision, then contact lenses can be recommended. With severe keratoconus, stretched collagen fibers can lead to swelling and scarring. A cornea transplant is sometimes necessary to restore vision if the condition is very severe. There are also specialized treatments that can be done to prevent the progression of the disease or help with recovery after a cornea transplant.

Vision correction laser surgery –LASIK – is dangerous for people with keratoconus, as it may further weaken the cornea and make the vision worse. Anyone with even a small degree of keratoconus should not have LASIK surgery.