uses reverse geometry contact lenses
sometimes referred to as 'corneal molds'. Flattening
the cornea reduces the focusing power
of the eye and thereby reduces myopia.Since
the amount of corneal flattening can
be accurately controlled, it is possible to bring the eye into correct
focus and compensate for the refractive error.. After the contact lens
is removed, the cornea retains its flattened shape for part or all of
the remainder of the day. A retainer lens must be used each day to maintain
the corneal flattening, or the myopia will revert to the pre-treatment
level. The treatment of hyperopia is basically the opposite, steepening
the cornea to reduce the hyperopia.
The procedure was first used
in the early 1960s when eye doctors noticed that some contact lens wearers'
vision improved after wearing their lenses.It has been reported in Chinese
history that sand bags were placed on the eyes at night in an effort
to prevent myopia though this was more likely to cause glaucoma.
Initially, only old-fashioned, hard contact lens material (PMMA) was
used. A series of lenses were needed, each lens flattening the cornea
a small amount until the desired results were attained. This took months
to years to accomplish.
Now, with the advent
of space-age polymers, computer-assisted lathes, and technological
advancement in the procedure, it is possible to achieve reduction
of myopia in a matter of days. This high tech version of Ortho-K
goes by many names. Among them are:
can be treated with
Ortho-K because the principle of flattening the cornea is effective
for both. In fact Ortho-K can benefit children greatly. Myopia
control is used to slow or stop the increase in axial length of
the eye that occurs in growing children who are becoming more
nearsighted each year. This may result in a lower prescription,
so the child won't have to wear the thick lenses he might otherwise
require by the time he/she is a teenager.
The cornea makes up about
two-thirds of the eye's total power to focus the light precisely
on the retina (receiving screen) which is located in the back of
the eye. By slight
modifications in the shape of the cornea, clear functional
vision may be restored for a period of time.
is temporary, therefore lens wear must be continued on a prescribed
wearing schedule to maintain the therapeutic effect of the myopia
reduction. This flattening is accomplished by compressing the
outer layer of the central cornea - the epithelium, thus flattening
it. The amount of flattening is approximately 6 microns per diopter
of myopia. A micron is one millionth of a meter; a human hair
is about 125 microns.There may also be some bending of corneal
tissue to achieve flattening. This would be similar to pressing
gently on a balloon producing a depressed surface. Top
Recently, several surgical
procedures have been developed to attempt to accomplish the same
purpose (i.e., changing the curvature of the cornea). Since the
cornea is soft, it can continue to change shape as time goes by.
The individual prescription may continue to vary leading to increased
dependence upon eyewear within years to just a few months after
the surgical procedure. Some surgical procedures (RK) produce scars
causing surface irregularities on the cornea, resulting in permanent
blurring that even glasses or contacts cannot eliminate. LASIK is
less likely to produce scarring of the cornea and has become a hot
topic in eyecare. Surgery is not an option for children or those
whose vision is changing. It does not stop the progression of myopia
in children or adults.
is accomplished with a contact lens device. Since the eye is flattened
and retains the flattened contour for a period of time the process
is sometimes referred to as corneal molding. The mold is a specially
designed contact lens. It is somewhat larger than a standard lens
but not very different in appearance. Comfort is generally excellent.
The lens is working as it is worn, whether you are sleeping or
awake. The procedure takes just hours (in mild cases) to a few
months (in very difficult cases) to reach good functional vision.
At that point, the wearing time is gradually reduced until a minimal-wear
time is established that maintains the corneal shape and good
functional vision. This assures continued clarity without the
gradual blurring that may accompany surgery. The cornea can easily
be fine-tuned by minor modifications to the retainer mold.
Topography - videokeratography
Ortho-K utilizes precise
instrumentation to accurately determine the corneal shape before
corneal topographer "maps"
the eye using thousands of points. The
topographer enables the ortho-k doctor to design the lens
for each eye instead of using
"stock" lenses. These
topographic maps or pictures are used to determine if the
corneal shape is changing in the correct manner. The typical
post-treatment map shows a central red ring (steepened area)
surrounding the flattened area. This flat area must be centered
over the pupil to provide maximum benefit.
Ortho-K is not only
an excellent alternative to the wearing of spectacles, but it
also frees the individual from the distractions caused by perspiration,
dust, wind weather and temperature. There are no more blind spots
caused by frame or lens edges. It is great to wear "regular" fashion
sunglasses, to get up at night or in the morning and see, to go
swimming and skiing, to drive in a convertible with the top down,
to work in the dust, grass or in the garden, and to be able to
see in cases of emergencies. Ortho-K might open new horizons to
you. People in occupations that are hindered by the use of glasses
or contacts may be good candidates for Ortho-K - pilots, policemen,
firemen, etc. Be sure to check with the regulations of your employer
prior to undergoing Ortho-K. Top
The Ortho-K specialist
measures the curvature of your cornea using the corneal
topographer. It is like having your picture taken and is painless,
taking about five minutes.Some doctors use software to help design
the lenses and diagnostic lenses may be placed on your eyes to
help determine the proper lens. Contact lenses for Ortho-K have
a reverse geometry design.
central portion of the contact lens fits closer to the eye
than a standard contact lens - exerting a gentle pressure.
It doesn't touch the cornea as there is a tear layer protecting
the eye.The reverse geometry
part of the lens surrounds the central visual zone and is
further away from the cornea than standard lenses allowing
room for the shift of epithelium.
your doctor prescribes overnight Ortho-K, expect results immediately.
Your vision should be markedly improved after the first night.During
the first few days or weeks your vision may fade later in the
day. Improvement should be noticed each day.
Generally only one pair of lenses are needed for the accelerated
therapy but additional lenses may be required to achieve desired
results. You will probably want an extra pair of lenses at the
end of therapy in case of loss. Your vision may regress to pre-treatment
levels while waiting for a new lens to arrive.
The practice of Ortho-K
requires a great deal of technical skill, specialized equipment
and considerably more office time and is therefore more costly
to the patient. Many practitioners don't consider myopia control
worth the time and effort. If a doctor is not trained in Ortho-K
it will not be an option or suggestion during an eye exam. It
is easier to offer contact lenses, glasses, or refractive surgery
to correct vision. Ortho-K doesn't produce a permanent result.
Retainer lenses are required to maintain the improvement. That
isn't bad. Because it isn't permanent, it is reversible.
Who Is a Candidate? - Indications
People of any
age who have low to moderate amounts of myopia, hyperopia
or astigmatism. Most doctors are comfortable treating myopia
of -6.00 diopters prescription or less but some are treating
much higher prescriptions.. Ortho-K initially was best suited
for myopia, but many doctors are now treating hyperopia (farsightedness).
Who Is Not a Candidate? - Contraindications
Acute and subacute
inflammations or infection of the anterior segment of the
Any eye disease,
injury or abnormality that affects the cornea, conjunctiva
disease that may affect the eye or be exacerbated by wearing
of ocular surfaces or adnexa which may be induced or exaggerated
by wearing contact lenses or use of contact lens solutions.
Any acute corneal
infection - bacterial, fungal or viral.
FDA - overnight Ortho-K
Ortho-K has been approved by the Federal Drug Administration.
Many lens designs have
been approved by the FDA. Several lens materials used for overnight
Ortho-K have also been approved. Ortho-K has been practiced safely
for over 40 years and overnight Ortho-K for 15 years.Clinical studies
to see more data on the risks and benefits of the overnight procedure
Consider this. Daily wear contacts are worn 12-16 hours per day.
Extended wear contacts are worn 24 hours per day. Ortho-K overnight
lenses are worn 8 hours per day. Which is safer?
Is Ortho-K in your
future? Only you and your eye doctor can decide that. To find
out if you are a candidate for accelerated Ortho-K, contact your