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What is keratoconus?

Keratoconus is an eye disorder in which your cornea slowly thins over time. The cornea also bulges out over time to form a cone-like shape.

The cornea is your eye’s outermost layer. It is a clear layer that caps the front of your eye. It helps protect the rest of your eye from germs and debris. It also helps focus light into your eye. With keratoconus, your cornea thins in the lower and central portions. Keratoconus can also cause swelling and scarring of your cornea. These changes to the cornea can cause vision problems, such as nearsightedness and astigmatism.

Keratoconus has different types. They are based on the shape and location of the thinned cornea. These types include nipple, oval, keratoglobus, and D-shaped keratoconus.

Keratoconus is not a common condition. It happens more often in young adults in their teens and twenties. It affects men and women in equal numbers.

What causes keratoconus?

The cause of keratoconus is not known. Some cases of keratoconus may be partly due to genes.

Some health conditions are linked to keratoconus and may contribute to the disorder. They include the following:

  • Down syndrome
  • Ehler-Danlos syndrome
  • Eye injury (especially from excessive eye rubbing or contact lens use)
  • Leber congenital amaurosis
  • Osteogenesis imperfecta
  • Retinitis pigmentosa
  • Retinopathy of prematurity
  • Vernal keratoconjunctivitis

Who is at risk for keratoconus?

Certain factors may increase your risk for the condition. A history of poorly-fitted contact lenses may raise your risk. Chronic eye rubbing due to eye irritation (for example, due to allergies) may raise your risk. And having a health condition linked to keratoconus may also increase your risk.

What are the symptoms of keratoconus?

Keratoconus causes nearsighted vision (myopia). This means you have trouble seeing objects that are far away. It also causes astigmatism. This is a problem with your eye forming a focused image on your retina. Together, these lead to blurry vision.

Keratoconus usually causes symptoms in both eyes. One eye may show symptoms before the other. One eye may be affected more than the other eye.

Symptoms often start during puberty and get worse until the fourth decade of life. You may not know you have keratoconus unless your eye doctor does special tests. Later, your vision may get much worse. Your eye doctor may evaluate you for keratoconus if your vision is worsening more than expected.

How is keratoconus diagnosed?

Your eye doctor will ask about your medical history and give you an eye exam. He or she will test the sharpness of your vision. You may need to have your eyes dilated for part of the exam. Your eye doctor may use a device to measure the curvature of your cornea.

The early stages of keratoconus may not be found unless your eye doctor is looking for signs of the disease. An imaging test called corneal topography may help your eye doctor make the diagnosis. This test shows changes in the shape of the cornea.

How is keratoconus treated?

Your treatment may vary according to the severity of your keratoconus. Your treatment options may also vary according to your specific type of keratoconus.

Early on, you may only need to wear glasses to correct the visual defect from your keratoconus. Special contact lenses are another option if you are unable to correct your keratoconus with glasses. Usually, these are the gas-permeable type. These contact lenses require careful fitting to your cornea.

Many people with keratoconus will not need any other treatment. But if your cornea becomes too scarred or is unable to tolerate a contact lens, you may need another kind of treatment. The traditional treatment in this situation is a corneal transplant. This surgery removes part or all of the original corneal thickness and replaces it with the cornea from a cadaver donor.

More recently, eye doctors have developed other surgical options to treat keratoconus. They both can help improve your vision. They include:

  • Artificial rings placed inside your cornea (corneal ring segments)
  • Artificial lenses placed inside your eye

Sometimes, eye doctors will use these treatments in combination to achieve better results. Each of these procedures has its own risks and benefits. Ask your eye doctor about what treatment or treatments make sense for you.

What are the complications of keratoconus?

Rarely, severe keratoconus causes a complication called corneal hydrops. This happens when part of your cornea breaks. This causes the fluid inside your eye to flow into your cornea abnormally. This can cause significant pain and swelling. It may also cause sudden vision loss.

You may need to wear special contact lenses or use special eye drops if you have corneal hydrops. Usually, corneal hydrops resolves in several weeks.

What can I do to prevent keratoconus?

Most cases of keratoconus are not preventable. You may be able to reduce your chance of getting keratoconus by:

  • Protecting your eyes from UV radiation with sunglasses
  • Making sure your contact lenses fit well
  • Getting treatment for any kind of eye discomfort (for example, from allergies)
  • Not rubbing your eyes

When should I call my eye care doctor?

Call 911 if you have sudden vision loss or sudden pain in your eye.

Key points

Keratoconus is a disorder in which your cornea gradually thins and becomes abnormally shaped over time. This causes a loss in visual sharpness.

  • Keratoconus causes nearsightedness and astigmatism and may make your vision blurry.
  • No one knows exactly what causes keratoconus, but certain medical problems may make it more likely.
  • Do not rub your eyes because this may cause or worsen keratoconus.
  • In its early stages, glasses or contacts may be the only treatment you need.
  • Some people with keratoconus will need other procedures, like corneal transplant surgery.
  • Advanced keratoconus sometimes causes corneal hydrops, which may bring on sudden vision loss.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.
  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your healthcare provider tells you.
  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your healthcare provider gives you.
  • Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
  • Ask if your condition can be treated in other ways.
  • Know why a test or procedure is recommended and what the results could mean.
  • Know what to expect if you do not take the medicine or have the test or procedure.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your healthcare provider if you have questions.
Online Medical Reviewer: Haupert, Christopher L., MD
Online Medical Reviewer: Walton-Ziegler, Olivia, MS, PA-C
Date Last Reviewed: 11/1/2016
© 2000-2018 The StayWell Company, LLC. 800 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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