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KERATOCONUS
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View the current Keratoconus Newsletter
A
primary focus of our practice is the care of
the keratoconus patient. Our strong focus and success in managing
keratoconus has led to patient referral from other doctors throughout
Southern California. Feel free to contact us if you require
information beyond what you find here or in the Keratoconus
Links offered at the bottom of this page.
What is Keratoconus?
Keratoconus is a disorder that causes progressive thinning and
distortion of the cornea - the clear dome at the front of the
eye. The cornea normally has a rounded shape, but in keratoconus
the thinned area bulges forward to produce a cone like protrusion.
This results in progressive distortion and reduced vision. Many
keratoconus patients experience blurred distance vision, glare,
light sensitivity, disturbed night vision, headaches and reading
problems, Keratoconus may affect only one eye but more commonly
occurs in both eyes. It affects people of all races and both
sexes. Most patients develop keratoconus in their late teens
to early twenties although it can begin at any age. Pellucid
marginal degeneration (PMD) is a corneal thinning disorder related
to keratoconus that primarily affects the inferior cornea.
Establishing the Diagnosis
Patients who develop keratoconus often experience reduced vision
as a first symptom. Nearsightedness and astigmatism (irregular
curvature of the eye) are often the first signs of the disorder.
Frequent prescription changes are another common sign of keratoconus.
Before computerized corneal topography became available, it
was sometimes difficult to establish a diagnosis of keratoconus,
especially if the practitioner was not familiar with the symptoms
in the early stages of the disease. The classic signs of keratoconus
include: Fleischer's ring (an iron colored ring surrounding
the cone), Vogt's striae (stress lines caused by corneal thinning)
and apical scarring (scarring at the apex of the cone).
Corneal
topography has facilitated the diagnosis of keratoconus, helping
establish the diagnosis earlier, follow progression more accurately
and differentiate keratoconus from other conditions. Please refer to
the “State of the Art
Testing and Equipment” section of our Services page for more
information.
 
Typical Keratoconus
Topography
Pellucid Marginal Degeneration
What Causes Keratoconus?
No one knows for certain what causes keratoconus. We do know
that keratoconus runs in families and that many patients who
have keratoconus report vigorous eye rubbing. Many patients
with keratoconus also have allergies, but the link to allergic
disease also remains unclear. Two theories for keratoconus have
been proposed:
- Keratoconus corneas are more easily damaged by minor
trauma such as eye rubbing.
- Keratoconus corneas lack the ability to self-repair
routine damage easily repaired by normal corneas.
Although contact lenses have been suggested as a possible cause
of keratoconus, this has not been proven and remains questionable.
We advise patients with keratoconus to avoid eye rubbing as
much as possible. Cold compresses applied to the eyes are helpful.
Newer anti-allergy medications such as Patanol or Zaditor are
also useful in managing itch and eye rubbing.
Treatment Options
- Custom
Prescription Glasses: In the early stages of Keratoconus and
pellucid degeneration, vision can be corrected with glasses. As
Keratoconus develops from mild form to more advanced stages, a
custom design lens that corrects for aberrations within the eye is
now available. It is called the iZon lens. We are great believers in
conservative treatment.
- Soft
Keratoconus Design: The use of regular soft lenses in
Keratoconus is limited because the soft lens drapes over the
irregular corneal surface and does not change the surface. There are
specialized thicker soft lenses that retain more of a rigid shape
masking the irregular corneal surface that can improve acuity.
- Rigid
Contact Lens: Rigid Gas Permeable (RGP) contact lenses are one
of the primary options for correcting Keratoconus vision. The rigid
lens functions as the new refractive surface of the eye. A tear film
filling is used to fill the space between the back of the contact
lens and the front of the eye. In more advanced Keratoconus, RGP
contact lenses are usually the best choice for visual
rehabilitation. There are numerous contact lens designs used to
treat keratoconus and pellucid marginal degeneration. The Rose-K is
an example of an exceptional and flexible lens design originally
introduced by New Zealand Optometrist, Dr. Paul Rose.
-
Piggyback System: This is a two lens system: an RGP lens is worn
on top of a soft lens. The RGP lens provides crisp vision and the
soft lens acts as a support base for the RGP.
- The
Hybrid Lens: This is a special design lens that combines a rigid
gas permeable center surrounded by a soft skirt. Currently there are
several hybrid contact lens designs available to meet the visual
needs of Keratoconus patients. This lens can correct for astigmatism
and is an option for early to moderate stage Keratoconus patients.
- Mini
Scleral and Scleral Gas Permeable Contact Lens (Therapeutic Device):
There are large diameter gas permeable lenses that rest on the white
part of the eye, called the sclera. The lens vaults over the entire
cornea. Underneath the lens is a fluid filled chamber that cushions
the cornea. Scleral lenses have many advantages because of their
size; they do not fall out and dust or dirt particles cannot get
underneath the lens. They are comfortable to wear because the
peripheral portion of the lens rests above and below the eye lid
margins. This lens can be prescribed to treat severe dry eye
patients.
- Intacs:
For early Keratoconus patients, there is a procedure that can
remodel the architecture of the cornea. Intacs are clear, thin
prescription inserts surgically placed in the peripheral cornea by
an ophthalmologist. This brief outpatient procedure re-establishes
the cornea to become more of a dome shape, therefore improving
vision. The procedure is less effective if there is any scarring
present near the center of the cornea.
- C3-R:
Patients with unstable corneas may be candidates for C3-R procedure.
This involves an in office application of ultra-violet light and
riboflavin drops. The C3-R procedure strengthens the collagen
cross-linking of the stromal fibers in the cornea. Increased
collagen cross-linking prevents the steepening and distortion of the
cornea. For more information please refer to the Keratoconus Inserts
link at the bottom of the page.
-
Corneal Transplant: If your cornea cannot tolerate a rigid
contact lens, or contact lenses no longer provide acceptable vision,
the next step is surgery. A cornea transplant, also called a
penetrating keratoplasty, is generally saved as a last resort.
Corneal transplant surgery may be required when the cornea is thin
and may have a lot of scarring. We work closely with several leading
corneal surgeons if the need arises. The procedure involved the
removal of the central portion of the diseased cornea and
replacement with a matched donor button of cornea. However, even
after a transplant, you most likely will need eyeglasses or contact
lenses for clear vision.
The key to a
successful contact lens fitting isn't as much the lens as it is the
skill and experience of the contact lens fitter. Fitting contact lenses
on a keratoconic cornea is delicate and time-consuming. You can expect
frequent return visits to fine-tune the fit and prescription. In some
cases the process can take many months. For many patients it is also a
continuing process which begins all over again as the condition
progresses. Improperly fitted contact lenses can cause extensive damage
to the cornea and can ultimately lead to a corneal transplant.
Fitting
patients with PMD can be especially challenging. In the early stages,
the central cornea is regular although highly astigmatic. Custom soft
toric contact lenses will often provide adequate performance and safety.
Keratoconus
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