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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
• Headaches from eyestrain
• 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 astigmatism (irregular curvature of the eye) and your eyesight is worsening rapidly. Your eye doctor also will likely 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.

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What triggers corneal thinning in keratoconus usually is unknown. Some experts believe that keratoconus may not be a single disorder but instead could stem from several different causes. If you have a habit of vigorously rubbing your eyes, it's possible to injure your corneas. A few people who frequently and vigorously rub their eyes develop keratoconus, though a cause-and-effect relationship remains unproved.

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These factors can increase your chances of developing keratoconus:

• Certain diseases. The risk of developing keratoconus is higher if you have certain inherited diseases or genetic conditions, such as Down syndrome. Keratoconus also is more likely in people with allergies or asthma, connective tissue disorders and some retinal diseases.
• Family history of keratoconus. Most people with keratoconus have no family history of the disease, but in some cases heredity may play a role.

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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 can also lead to anxiety.

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If you're having difficulty with your vision, you'll likely to start by seeing an ophthalmologist or optometrist. If it's determined that a corneal transplant may be needed, you may be referred to an ophthalmologist who specializes in eye surgery.

Because appointments can be brief and there's often a lot of ground to cover, it's a good idea to be prepared. Here's some information to help you get ready, and what to expect from your eye doctor.

What you can do

• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment. Also, write down key personal information, including any major stresses or recent life changes.
• Make a list of all medications, including eyedrops, vitamins and supplements that you're using or taking.
• Ask a family member or friend to come with you. Sometimes it can be difficult to absorb all the information provided during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions will help you make the most of your time together. List your questions from most important to least important in case time runs out. For keratoconus, some basic questions to ask your doctor include:

• What do you think is causing my symptoms?
• Are there any other possible causes for my symptoms?
• Do I need any special tests?
• Is this condition temporary?
• What treatments are available? Which do you recommend?
• Are there alternatives to the primary approach that you're suggesting?
• I have another health condition. How can I best manage these conditions together?
• Are there any brochures or other printed material that I can take with me? What websites do you recommend?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment.

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over points you want to spend more time on. Your doctor may ask:

• What types of signs and symptoms have you been having?
• When did you begin experiencing symptoms?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• Does anything seem to improve your symptoms?
• What, if anything, appears to worsen your symptoms?
• Is there anyone in your family who has keratoconus?

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Your ophthalmologist can diagnose keratoconus during a routine eye exam, but more sophisticated tests may be done to determine the exact shape of your cornea. Tests to diagnose keratoconus include:

• Eye refraction. In this standard vision test, your eye doctor uses special equipment that measures your eyes to check for astigmatism and other vision problems. This may include a measurement taken by a computerized refractor, which automatically checks your eyes' focusing power, or by retinoscopy, a technique that evaluates light reflected by your retina. Then your eye doctor may ask you to look through a mask-like device that contains wheels of different lenses. This helps your doctor find the combination of lenses that gives you the sharpest vision.
• Slit-lamp examination. This test shines a vertical beam of light on the surface of your eye while the eye doctor looks through a low-powered microscope to view the shape of your cornea. The test may be repeated after eyedrops are used to dilate your pupils so that the doctor can view the back of your cornea.
• Keratometry. A circle of light is focused on your cornea, and the reflection is used to evaluate your cornea's curvature.
• Computerized corneal mapping. Optical scanning techniques, known as computerized corneal topography, can take a picture of your cornea and generate a topographical map of your eye's surface.

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Treatment for keratoconus depends on how severe it is and how fast it's progressing. Mild to moderate keratoconus can be treated with eyeglasses or contact lenses. For most people, the cornea will stabilize after a few years, without causing severe vision problems. In about 10 to 20 percent of people with keratoconus, however, the cornea becomes scarred or they're unable to continue wearing contact lenses. In these cases, surgery might be necessary.

Lenses
For most people with keratoconus, contact lenses are the most effective treatment.

• Eyeglasses or soft contact lenses. Glasses or soft contact lenses can correct blurry or distorted vision in early keratoconus. But people frequently need to change their prescription for eyeglasses or contacts as the shape of their corneas change.
• Rigid gas permeable contact lenses. Hard contact lenses are often the next step in treating progressing keratoconus. Rigid lenses may feel uncomfortable at first, but many people get used to them.
• Piggyback lenses. If you don't like the feel of rigid lenses, your doctor may recommend "piggybacking" a hard contact lens on top of a soft one. Fitting a combination of lenses takes a lot of precision, so be sure you work with a doctor experienced with this technique.
• Hybrid lenses. Also for people who can't tolerate hard contact lenses, these contacts have a rigid center with a softer ring around the outside for increased comfort.
• Customized contact lenses. Rigid gas permeable lenses can be custom made based on topographical measurements of your corneas.
• Scleral contact lenses. These lenses are useful for irregular changes in your cornea. Instead of resting on the cornea like traditional lenses do, scleral contacts sit on the white part of the eye (sclera) and vault over the cornea.

If you're using rigid or scleral contact lenses, make sure to have them fitted by an eye doctor with experience in treating keratoconus. You'll also need to have regular checkups and refittings. A poor-fitting hard contact lens can further damage your corneas if you have keratoconus.

Surgery
You may need surgery if you have corneal scarring, extreme thinning of your cornea or poor vision even with the strongest prescription lenses, or if you can't wear any type of contact lenses. Several surgeries are available, depending on the location of the bulging cone and the severity of the disease. Surgical options are:

• Corneal inserts (intrastromal corneal ring segments). During this surgery, your doctor inserts two tiny, clear, crescent-shaped plastic inserts into your cornea to flatten the cone, support the cornea's shape and improve vision. First you're given a local anesthetic around your eye to numb it. Your surgeon makes a small cut in your cornea, either with a precision blade or a laser, and places the inserts in specific locations based on your cornea's shape. The incision is closed with stitches, and a soft lens is placed over your eye to protect it while it heals.

  Although corneal inserts can restore a more normal corneal shape and keep keratoconus from progressing, many people still need to wear corrective lenses following the procedure. But the surgery makes it easier to fit and tolerate contact lenses. Since the surgery is reversible, some people choose to have corneal inserts before considering keratoplasty.

• Cornea transplant (keratoplasty). If you have corneal scarring or extreme thinning, you'll likely need a corneal transplant, called keratoplasty. Lamellar keratoplasty is a partial-thickness transplant, in which only a section of the cornea's surface is replaced. Penetrating keratoplasty is a full-cornea transplant, in which an entire portion of your cornea is replaced. A deep anterior lamellar keratoplasty (DALK) preserves the inner layer of the cornea, called the endothelium. It helps avoid rejection caused by the endothelial cells in a full-thickness transplant.

  During a keratoplasty, you may have a general anesthetic or your eye may be numbed with a local anesthetic. Your doctor removes a button-shaped portion of your cornea, replacing it with a similar-sized button from a donor cornea. Stitches and a soft lens are placed to protect your eye as it heals. Recovery after keratoplasty can take up to one year, and you'll likely continue to need rigid contact lenses to have clear vision. It might take several years before you receive the full benefit of the transplant for improved vision. Corneal transplant is generally very successful, but possible complications include graft rejection, a dilated or fixed pupil, infection, cataract, and glaucoma.

Emerging treatment
A treatment for keratoconus, called collagen cross-linking, shows promise. After having riboflavin drops applied to your cornea, you're exposed to ultraviolet A (UVA) light. The procedure strengthens the cornea, with the goal of preventing further thinning or bulging. The treatment is still in the testing phase in the United States, and additional study is needed before it becomes widely available.

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Most cases of keratoconus aren't preventable, but you can take some steps to be sure you don't cause it yourself:

• Use care when rubbing your eyes. If you vigorously rub your eyes every day, you may damage your corneas in a way that can lead to keratoconus. Although the relationship between eye rubbing and keratoconus hasn't been proved, if you do need to rub or wipe your eyes, do so as gently and as little as possible. Some people don't realize the extent of their eye-rubbing habit until a family member or friend points it out, so pay attention if someone has mentioned it.
• Follow instructions when wearing rigid contact lenses. If you wear hard contact lenses, be sure to use them as directed and have the fitting checked regularly to avoid damage to your eyes. Never use someone else's hard contact lenses.

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.