Filed under: Children's Health
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 typically begins during puberty or in your late teens. The condition may progress slowly for 10 years or longer.
In the early stages of keratoconus, vision problems can be corrected with glasses or soft contact lenses. As keratoconus progresses, you may have to be fitted with special rigid gas permeable contact lenses. Advanced keratoconus may require surgery.
Signs and symptoms of keratoconus may change as the disease progresses. They include:
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.
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.
These factors can increase your chances of developing keratoconus:
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.
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
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:
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:
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:
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.
For most people with keratoconus, contact lenses are the most effective treatment.
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.
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.
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.
Most cases of keratoconus aren't preventable, but you can take some steps to be sure you don't cause it yourself: