Keratoconus, often abbreviated to “KC”, is a non-inflammatory eye condition in which the normally round dome-shaped cornea progressively thins causing a cone-like bulge to develop. This results in significant visual impairment.
Keratoconus is an uncommon condition, which causes a bulging of the cornea from its normal round shape to a bulged cone shape. This is caused by a progressive thinning and steepening of the central cornea. As the cornea steepens and thins, the patient experiences a decrease in vision which can be mild to severe depending on the amount of corneal tissue affected.
Generally, the vision can be corrected in mild cases with spectacles or gas permeable contact lenses. As the condition worsens, specifically designed keratoconic contact lenses are needed to maintain good visual acuity. Although this disease does not cause blindness, most patients will require keratoconic contact lenses. In the severe cases of keratoconus, about 20% of patients will eventually need a corneal transplant.
What causes Keratoconus?
Keratoconus occurs in about 0.15% to 0.6% of the general population. The onset of keratoconus occurs during the teenage years with a mean age of 16 years. There is no significant geographical, cultural, or social pattern to its distribution. Keratoconus shows no gender predilection and is bilateral in over 90% of cases. The diagnosis of the disease in the second eye occurs on average about five years after the first eye was diagnosed.
The disease process is active for about five to ten years, then it generally becomes stable for many years with little change. During the active stage, the changes in the corneal shape are rapid and frequent, requiring many contact lens changes to keep a good fitting contact lens on the cornea.
Hereditary factors seem to play some role in the development of keratoconus. Families that have one member with keratoconus, the incidence of keratoconus in other family members are 8% through the dominant or recessive trait. Keratoconus is more common with patients that have atopic dermatitis, connective tissue disorders, retinitis pigmentosa, Down syndrome, Crouzon’s syndrome and Marfan syndrome. Although a lot of research is always looking for a definite cause of keratoconus, there is no clear-cut cause as of today.
What are the symptoms of Keratoconus?
The first symptom that occurs is blurring and distortion of vision in the late teens or early twenties. In the early stages, spectacles or contact lenses will be required with many changes as the rapid changes occur to the cornea. Ghost images, double vision with one eye, and multiple images are very common complaints. As the cornea rapidly changes, many patients experience a sudden clouding of vision in one eye. This occurs from the distortion of many areas of the cornea with different powers of prescription creating multiple confusing images.
How is Keratoconus treated?
Rigid gas permeable contact lenses are the only way to correct keratoconus as it advances. It is extremely important that the lenses are fitted with great care as the disease progresses. Most keratoconus patients require frequent checkups and lens changes to maintain good vision and comfort.
The frequent monitoring of the corneal shape is imperative. Dr. Anderson uses a computerized corneal topographer, which maps 8,000 points on the cornea to provide a color-coded printout. This printout is stored in the central computer system, and is available to be e-mailed to any location. The advantage of using a corneal topographer is that Dr. Anderson is able to view the cone, even if it is off center.
Even though the onset of keratoconus is the teenage years, documented cases have been reported as early as six years of age. As a parent, Dr. Anderson places his trust in the corneal topographer to help diagnosis and rule out any corneal problems for all children.
One of the rigid contact lenses that Dr. Anderson uses is the Rose-K lens. Its complex lens geometry takes into account the conical shape of the cornea. The entire lens fits better over the eye and it provides outstanding patient comfort and visual acuity. If advanced form of keratoconus develops, Dr. Anderson will diagnosis Lines of Vogt in the posterior cornea with excessive thinning and corneal scarring.
Even the best-designed contact lens may not be able to help the advanced form of keratoconus. The only alternative is surgery. These include a corneal transplant, special heating of the cornea (thermokeratoplasty) or adding additional corneal tissue (epikeratophakia).
What happens if I need a corneal transplant?
Once we decide you need a corneal transplant, Dr. Anderson will consult with a corneal specialist. Dr. Anderson will e-mail all of your records, including external pictures of your cornea, to that ophthalmologist. You will have a surgical consultation with the corneal specialist to verify that a corneal transplant is the agreed upon action. Then your name is put on a list at the local eye bank. Usually the wait is short.
Before a cornea is released for transplant, the eye bank tests the human donor for the viruses that cause hepatitis and AIDS. The cornea is carefully checked for clarity.
The corneal specialist may request that you have a physical examination and other special tests. If you usually take medications, ask the specialist if you should continue them.
The day of surgery:
Surgery is often done on an outpatient basis. You may be asked to skip breakfast, depending on the time of your surgery. Once you arrive for surgery, you will be given eye drops and sometimes medications to help you relax. The operation is painless. Anesthesia is either local or general, depending on your age, medical condition and eye disease. You will not see the surgery while it is happening, and will not have to worry about keeping your eye open or closed.
The eyelids are gently opened. Looking through a surgical microscope, the corneal specialist measures the eye for the size for the corneal transplant. The diseased or injured cornea is carefully removed from the eye. Any necessary additional work within the eye, such as removal of a cataract, is completed. Then the clear donor cornea is sewn into place. When the operation is over, the specialist will usually place a shield over your eye.
If you are an outpatient, you may go home after a short stay in the recovery area. You should plan to have someone else drive you home. An examination at the doctor’s office will be scheduled for the following day.
You will need to:
- Use the eye drops as prescribed;
- Be careful not to rub or press on your eye;
- Use over-the-counter pain medicine, if necessary;
- Continue normal daily activities except exercise;
- Ask your doctor when you can begin driving;
- Wear eyeglasses or an eye shield as advised .
The corneal specialist will decide when to remove the stitches, depending upon the health of the eye and rate of healing. It will be several months, at least, before stitches are removed.
What complications can occur?
Corneal transplants are rejected 5% to 30% of the time. The rejected cornea clouds and vision deteriorates. Most rejections, if treated promptly, can be stopped with minimal injury.
Warning signs of rejection are:
Persistent discomfort; Light sensitivity; Redness; Change in vision
Any of these symptoms should be reported to the corneal specialist or Dr. Anderson promptly.
Other possible complications include:
Infection; Bleeding; Swelling or detachment of the retina; Glaucoma
All of these complications can be treated. A corneal transplant can be repeated, usually with good results, but the overall rejection rates for repeated transplants are higher than for the first time around. Irregular curvature of the transplanted cornea (astigmatism) may slow the return of vision but can also be treated. Vision may continue to improve up to a year after surgery. Even if the surgery is successful, any other eye conditions, such as macular degeneration (aging of the retina), glaucoma or diabetic damage may limit vision after surgery.
Even with such problems, corneal transplantation may still be worthwhile. A successful corneal transplant requires care and attention on the part of the patient, corneal specialist and Dr. Anderson. However, no other surgery has so much to offer when the cornea is deeply scarred or swollen. The vast majority of people who undergo corneal transplants are happy with their improved vision.
- National Keratoconus Foundation: http://www.nkcf.org