CURRENT GLAUCOMA
TREATMENT MODALITIES
Although glaucoma remains the second leading cause of blindness
in the United States, considerable progress has been made in its management. The disease
can be controlled effectively and sight preserved for those patients whose condition is
diagnosed and treated early.
Knowledge of the most common risk factors can help physicians
identify glaucoma "suspects" and refer for sight saving (not sight restoration)
treatment. Medical assistance in referring is critical because the disease, in many
instances, presents no symptoms to alarm the patient.
Most glaucoma sufferers, of course, are adults aged 40 or more.
That is the patient category addressed by this article. An estimated two out of three
glaucoma victims in this mature age group exhibit elevated intraocular pressure when
tested. Pressure remains the foremost of all risk factors, yet the patient may not know
it's anything out of the ordinary.
So insidious is the disease that the patient may experience
gradual loss of vision - central and/or peripheral - and not realize it. A test for
intraocular pressure may even prove inconclusive because approximately one out of three
glaucoma victims suffers from the low pressure type of glaucoma. In these cases, the
pressure may be in the normal range of 12 to 21 millimeters of mercury.
THE OPTIC NERVE
A definitive diagnosis can be made only by means of a thorough
examination of the optic nerve. If the disease is present, it will be manifest in damage
to nerve fibers and blood vessels.
Any long term decrease or interruption of blood flow to the optic
nerve can cause ocular damage leading to glaucoma. This would establish as candidates for
glaucoma individuals with high or low blood pressure, blockage in the carotid, coronary
disease or with a history of migraine headaches. Diabetics and heavy smokers are at high
risk because of the negative effects of both the disease and the habit on blood
circulation.
Blacks are more at risk than whites because, for reasons unknown,
their intraocular pressure is more difficult to control and they seem to sustain more
nerve damage. They seem to scar faster after surgery, causing premature post-op drainage
problems. Experience also indicates that blacks are less compliant in following treatment
instructions.
Anyone with a family history of glaucoma is 25% at risk of
inheriting the disease. It should be noted also that individuals with myopia are more
inclined than others to contract glaucoma.
TREATMENT MODALITIES
In the normal eye, aqueous humor circulates freely through the
anterior and posterior chamber. The fluid, produced constantly by the ciliary body, drains
through the trabecular meshwork, back into the bloodstream. Glaucoma develops when
production of fluid increases, or filtration is no longer adequate. Pressure rises in the
eye, causing damage to the optic nerve.
Three different treatment modalities are prescribed, each
depending on how far the disease has progressed. Drops (sometimes pills) are the first and
most conservative treatment method. If drops do not ameliorate the condition, laser
treatment is applied. Should that approach prove unsuccessful, surgery may be necessary.
All three are designed to reduce intraocular pressure.
Timoptic and betagan -which are beta blockers - decrease the
production of fluid. Pilocarpine increases filtration or drainage out of the eye. Propine
achieves both functions, but now as well as either of the alternative drugs. Iopidine, a
new drug, reduces pressure nicely, but only for two to three months. These drugs are not
inexpensive, they do have side effects and they generally have to be taken for the rest of
the patient's life.
Pills such as carbonic and anhydrase inhibitors may sometimes be
prescribed. However, they can have multiple side effects including drowsiness, loss of
appetite, loss of weight and stomach upset. Certain pills may be given to the patient
awaiting surgery, or taken if neither the drops nor laser treatment is successful.
ARGON LASER
In the case of open angle glaucoma - the most common type - the
argon laser is used to increase filtration. The operation, performed in the office with a
success rate of 80 to 85%, is called argon laser trabeculoplasty. It is a painless
procedure, with drops numbing the eye, in which the laser shrinks the trabecular meshwork.
Laser treatment effectively reduces intraocular pressure.
However, in four to five years after treatment, the pressure will increase again. If the
laser was effective the first time attempted, it can be repeated at least once, sometimes
twice.
SURGICAL PROCEDURE
A small section of the trabecular meshwork may be removed by a
surgical procedure know as a trabeculectomy. This operation, also 80 to 85% successful, is
done to create artificial filtration. There is a problem with this treatment method,
however. The surgical area tends to scar down and close up, blocking fluid drainage after
a few years.
To prevent this scarring, I now apply mitomycin-C to the surgical
site at the time of surgery. This treatment allows drainage to flow freely for a much
longer time: how much longer remains to be seen, since this is a new procedure.
Of interest to the physician is the recent FDA approval for use
of the holmium laser in performing trabeculectomies. Good results are expected also of the
erbium laser which is pending FDA approval.
Although not included in my armamentarium, a new tube shunt
procedure is performed by some ophthalmologists in cases of advanced glaucoma when other
procedures have proved ineffective. With this surgical approach, a silicon tube is
inserted in the anterior chamber to keep the aqueous humor circulating.
As a last resort, and only with very sick eyes, cyclodestructive
procedures may be used to freeze and destroy the fluid-producing ciliary body. The
greatest challenge here is to retain enough of the tissue and ciliary process to keep some
fluid flowing. The eye cannot function without any aqueous humor.
CONCLUSION
Approximately 2% of the adult population over age 40 suffers from
glaucoma, much of which is stealing sight without warning symptoms. Highly effective
treatment methods are available to manage the disease. The challenge to physicians is to
help identify individuals who, based on various characteristics and conditions, are prime
candidates to have or contract glaucoma.
Individuals aged 40 or older should have a professional eye
examination by an eye doctor once a year. The checkup must include a thorough evaluation
of the optic nerve. Anyone on regular medication, or with glaucoma in the family history,
should see an eye doctor more often. For such individuals, the optic nerve examination is
even more important.
Early detection and treatment will enable the ophthalmologist to
control the disease and preserve what vision remains. Lost sight cannot be restored, but
blindness can be prevented.
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