Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at April 15, 2016

Keratoconus is a condition that affects the cornea of the eye. Normally, the cornea is a strong, clear dome-like lens that both protects and focuses the sensitive inner workings of the eye. But under certain conditions, that lens begins to get weaker due to a weakening in the protein and collagen fibers. This causes a change in corneal shape that in turn distorts vision.


Definition & Facts

Keratoconus is a disorder of the eye that is progressive in nature. It can affect only one eye or both eyes. In cases where both eyes are affected, each eye may exhibit different symptoms and degrees of severity. Often just one eye is initially affected and the second eye becomes affected later on.

When the corneal fibers weaken, free radicals can cause oxidative stress to the already compromised tissue of the cornea. Once keratoconus begins, it will need continual monitoring and treatment from that point forward throughout the person's life.

Symptoms & Complaints

For many people, keratoconus first announces itself when nearsightedness (difficulty seeing farther away) begins to get worse. Gradually, the affected eye also develops astigmatism, which contributes to blurred vision or distorted vision.

As keratoconus progresses, the person may begin to become more sensitive to bright light and glare, with the onset of "halos" in the vision or double vision when one eye is kept closed.

Sometimes the symptoms will continue to get worse and worse. But sometimes the symptoms will stop at some point, or at least cease to get worse. Researchers are still working to discover why this occurs.


Keratoconus is now thought to have a genetic link. This is because more cases are seen in families where one or both parents have the disorder. Researchers continue to explore the causes of keratoconus, but one promising lead links corneal weakening to an enzyme imbalance in the eye.

However, not all cases of keratoconus are genetic. Overexposure of the cornea to harmful UV (ultraviolet) rays, chronic eye infections or irritations, contact lenses that do not fit well and constant rubbing of the eyes can also trigger the onset of keratoconus. Researchers have also seen a link between the development of keratoconus and the presence of certain allergies or medical issues.

Diagnosis & Tests

Because keratoconus is thought to be passed from parent to child genetically, it is important to have children tested starting around age 10, even though most cases don't begin to produce symptoms until the teens or even as late as the 20's.

Keratoconus occurs when the natural round dome-shape of the cornea begins to resemble a cone instead. So it is the onset of the changing corneal shape that confirms a diagnosis of keratoconus.

It is important to be examined by a eye doctor, who can detect both the change in corneal shape and a transition from the formerly smooth dome to a wavy cone. It is also important to be aware of symptoms and to share these with the examining doctor, since these symptoms can be useful in confirming the diagnosis.

For a complete confirmation of diagnosis, the eye doctor will actually measure the shape of the cornea. This test is called corneal topography. The doctor takes a photo of the cornea and analyzes its shape. The test is quick and definitive.

Treatment & Therapy

Once keratoconus is diagnosed, the initial treatment phase begins. Usually the first step is to wear eyeglasses or soft lenses with a corrective prescription. For many people, making sure they always have eyeglasses or soft contacts with an up-to-date corrective prescription provides sufficient treatment.

For some people whose keratoconus does not seem to respond well to eyeglasses or soft contacts, hard contact lenses may be prescribed instead. For people who have more advanced symptoms, there are some additional procedures that can be helpful:

  • PTK. Phototherapeutic keratectomy, or PTK, removes a small scar that often forms at the tip of the cone-like cornea. This can make it possible for the person to comfortably wear contact lenses as a form of treatment.
  • Cornea collagen cross-linking. Cornea collagen cross-linking is a treatment to smooth out the cone-like shape of the cornea using implants. Once inserted, the person is often able to wear contacts more comfortably and continue with treatment.
  • Corneal transplant. As a treatment option, a corneal transplant is usually reserved as an option of last resort when other procedures have failed. The operation removes the cone-shaped portion of the central cornea and a donor's smooth cornea is inserted in its place. After the operation the person will typically wear contact lenses when continuing treatment.
  • Piggybacking contact lenses. With this treatment, the person wears a soft contact lenses against the cornea and a hard contact lens on top of the soft lens to minimize the discomfort of the hard lens.
  • Custom contact lenses. Custom contact lenses can greatly ease discomforts caused by the cone-shaped cornea.
  • Hybrid contact lenses. Hybrid lenses combine a rigid and soft lens.

Prevention & Prophylaxis

At this time, there is no known method of preventing the genetic form of keratoconus. However, for cases of keratoconus that are prompted by eye rubbing/allergies, UV exposure, ill-fitting contact lenses or chronic irritation in the eyes, aiming to avoid these risks is a promising path to avoid developing keratoconus in the future.

In addition, ensuring adequate intake of foods (such as fruits and vegetables) that are naturally high in antioxidants such as vitamin E, vitamin C, and beta-Carotene can help improve the health of the cornea.