FOR PATIENTS
Do you have Keratoconus?
DO YOU HAVE KERATOCONUS?
What is keratoconus?
The surface of the cornea, the transparent dome-shaped front part of our
eyes is their most important focusing lens. To function properly it must
be exquisitely smooth and appropriately shaped. Keratoconus causes the
central area of the cornea to become thinner and bulge outward thereby
impairing its ability to focus.
The tendency to develop keratoconus is present at birth and is estimated to affect 1 person in 2000. In some patients the disease remains mild and they will continue to have good functional vision with glasses. In many keratoconus will progress to the point that vision is no longer adequately imporved with glasses. The disease generally affects one eye more than the other by the time it stabilizes, usually (but not always) in the third and fourth decades.
What are my options when glasses no longer provide functional
vision?
Rigid (hard) gas-permeable (RGP) contact lenses can greatly improve vision
of keratoconic eyes when glasses are no longer effective. This unique
capability is due to the smooth layer of tears they enclose over the irregular
surface of the cornea that masks its optical distortions.
Can RGP contact lenses be worn by everyone?
Traditional RGP contact lenses are designed to rest on the cornea, the
most sensitive tissue of the human body. This is why the wearing comfort
of these lenses is dependent on being able to minimize the pressure/friction
generated as they slide over the corneal surface during each blink. The
development of special keratoconus designs have increased their success
in the hands of practitioners who have developed the special skills needed
to maximize their effectiveness. However, even the best fitted keratoconus
contact lenses may not achieve this goal, especially if the tear supply
is insufficient to provide adequate lubrication.
If I can’t wear traditional RGP contact lenses, what are
my other non-surgical options?
The piggyback system (wearing a traditional RGP lens over a soft contact
lens), though less convenient and more awkward, can sometimes be better
tolerated than an RGP contact lens alone. Another option, the hybrid lens
(hard center and soft skirt) is rarely a satisfactory long-term solution.
When these modalities are not tolerated, the Boston Scleral Lens Prosthetic
Device (BSLPD) can be very effective.
How is the Boston Scleral Lens Prosthetic Device different?
The BSLPD avoids all contact with the sensitive cornea. Instead, it rests
entirely on the sclera (the tough, relatively insensitive white tissue
of the eye) and creates a pool of artificial tears over the cornea that
functions as a unique liquid eye bandage. This is why the BSLPD can be
worn comfortably when other types of contact lenses have failed and why
it never decenters, becomes dislodged or traps foreign bodies. Moreover,
even severe dry eye is not an impediment to their wearing tolerance. In
fact, their liquid eye bandage has been a very successful treatment for
this condition.
What are the limitations of the BSLPD?
The success rate for achieving all day wearing comfort in patients who
have been unable to tolerate other contact lens options exceeds 90%. The
principal limiting factor is vision. In some eyes with advanced keratoconus,
the severe optical aberrations may not be fully corrected with hard contact
lenses including the BSLPD. Satisfactory vision can be achieved in many
cases by wearing glasses over the contact lenses that correct residual
astigmatism. The indication for corneal transplant surgery in keratoconus
is failure of the BSLPD to provide satisfactory vision.
How can my eyecare practitioner determine if I am a candidate
for the BSLPD?
The process of custom designing the BSLPD is costly, time consuming and
skill intensive. For these reasons, we accept only those patients who
are significantly visually disabled and have exhausted all other non-surgical
options. If your vision with traditional RGP contact lenses is adequate
but their wearing tolerance is poor, it is very likely that the BSLPD
will enable you to avoid surgery. On the other hand, if the vision provided
by traditional RGP contact lenses is unsatisfactory, it is unlikely that
our device will work for you unless it is largely due to poor lens centration.
(The BSLPD is always well centered.) Your contact lens specialist can
estimate the potential vision correction of our device by measuring your
acuity over a larger hard contact lens designed to center adequately.
Why shouldn’t I have corneal transplant surgery instead
of bothering with contact lenses?
As an invasive surgical procedure, corneal transplant surgery poses the
risk of potentially serious complications even under the best circumstances.
Young people are at greater risk for graft rejection. Furthermore, transplanted
corneas have a limited lifespan and the younger the patient, the greater
the probability that it will eventually fail and require another corneal
transplant.
Because of the absence of blood vessels in the cornea, the healing process is slow and it may take a year or longer before the shape of the transplanted cornea (and effectiveness as a focusing lens) has stabilized. During this time, vision in this eye is often not functional. Even after flawless surgery, the healing process can be uneven causing the corneal graft to become warped and create abnormal astigmatism. Approximately 25% of eyes with successful corneal transplants do not achieve good quality vision with glasses and require hard contact lenses for satisfactory eyesight. Yet their distorted shape can pose a significant challenge to fitting traditional RGP contact lenses. When they are too unstable and uncomfortable to wear, the BSLPD can offer an excellent visual result.
Corneal specialists agree that it is best to exhaust all non-surgical
options before undergoing corneal transplant surgery.
For more information on keratoconus, visit:
The National Keratoconus Foundation (NKCF).
Treatment Options
for people with Keratoconus
(PDF Download)
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