Keratoconus
Keratoconus
is a condition of the cornea. The word
keratoconus is formed from two Greek words, kerato, meaning cornea, and konus,
meaning cone. The normal cornea is the clear
"watch-glass" covering of the front of the eye. The cornea is generally shaped
like a dome or sphere. It is primarily responsible for surface protection of the
eye and performs a greater degree of light focusing than any other part of the
eye.
Keratoconus gradually causes the central area
of the cornea to weaken, thin, or bulge. It
eventually distorts from its more spherical shape to a cone shape.
This distortion may cause significant changes in
vision which may begin in the late teen years and may not stop until age 40.
While keratoconus can be an inherited bilateral
(two eye) condition, many patients have no clear inheritance pattern.
It has been estimated to occur in 1 out of every 2,000 persons.
The
earliest changes of keratoconus may require frequent changes of glasses.
As the corneal distortion worsens, contact
lenses may be required to obtain adequate vision. In
this case, contact lenses mask the warp or cone-like changes of the underlying
cornea. Generally, most keratoconus patients can
be safely managed with contact lenses yielding good vision and comfort.
Cautions
People who
handle their keratoconus problems successfully develop their own coping
mechanisms. Sunglasses are advised to reduce glare symptoms. If
contacts are worn, and since the fitting of these lenses is especially
difficult, we advise an extra pair in the event of loss.
Be alert to any sudden changes in your vision. Contact us immediately if
you experience excessive blur, scratchiness, watering or discharge. Women should
take special care with cosmetics. We advise that all keratoconus patients
wear goggles when swimming and wear safety eyewear when engaged in yard work,
hazardous work environments and athletics.
FAQ & Keratoconus
Q Why do I have keratoconus and what causes the condition?
A Keratoconus is a genetically determined condition. Unfortunately, the exact inheritance pattern has not yet been elucidated.
Q You have said that keratoconus is inherited. How can I help my children avoid it?
A You can help your children best by insuring that they have good eye care and annual eye examinations by a competent optometrist who knows your eye history and understands the condition.
Q What can I do to keep the condition from progressing?
A Currently, no treatment -- medical, surgical or contact lens related -- can retard the progress of the condition. It may be damaging to corneal tissue to delay replacing your contact lenses when corneal changes indicate that such changes are necessary.
Q Why are contact lenses for keratoconus so difficult to fit, so uncomfortable and so expensive?
A Since the keratoconic cornea is irregular, additional time and trials may be necessary to achieve the best fit. Materials, time and remakes to achieve these goals cost more money than a normal fitting. The lens need not be more uncomfortable than any other gas permeable lens on a normal eye.
Q Which is the best kind of contact lens to wear?
A The best lens for any keratoconic eye is one that permits the best corneal health, while allowing for the best visual acuity, without sacrificing comfort. A lens material that allows for the least corneal insult while remaining stable during production and wearing is best.
Q Why must we wear rigid contact lenses? Why not soft contact lenses?
A While the majority of keratoconus patients achieve their best visual acuity with gas permeable contact lenses, some early keratoconus patients do well with astigmatic or toric soft lenses and some later keratoconus patients need either hybrid soft gas permeables or even "piggy-back" (gas permeables worn over a soft lens carrier) lens combinations.
Q Why is my vision not sharp, even with an gas permeable contact lens? Why do I have multiple vision?
A The typical keratoconic cornea is distorted and thinned in various areas. Each distortion in shape creates areas of different depth in the sub-lens tear layer. Each of these pools will give an unclear refraction. As the gas permeable contact lens moves with each blink, vision is dynamically unstable as the pools empty and refill throughout the various stages of the blink. Similarly, multiple vision is an effect of areas of different refraction in the cornea caused by localized thinning and variation in curvature.
Q Why is my vision so much less sharp when I remove my contact lenses?
A Because the cornea is thinner, it's structurally less stable. This instability allows the cornea to be more easily molded. The effect of this molding is a surface of topography and, therefore, refraction different from that of the same cornea in a fresh state. The same sort of molding can occur if you sleep with your eyes resting on your hands.
Q How will I know if I need a corneal transplant?
A Conventional wisdom dictates the need for a corneal transplant when you can no longer be fitted with a contact lens that is tolerable to you and provides you with adequate vision for your needs.
Q Need I be worried about becoming pregnant, giving birth or nursing around the time of my corneal transplantation surgery?
A In general, large doses of steroid medications are used to stabilize corneal grafts and, in some cases, glaucoma medications are required to reduce intraocular pressure. It is best to plan pregnancy, birth and lactation with these considerations in mind. Arranging joint consultations with your corneal surgeon and your obstetrician/gynecologist can also prove helpful.
Links for Keratoconus
National Keratoconus Foundation
Center for Keratoconus
Corneal Transplants and Keratoconus
100 North Rancho Road, Suite #1
Thousand Oaks, CA 91362
Phone (805)495-3937 Fax (805)373-9843
E-Mail