| What
is Histoplasmosis? Histoplasmosis
is a disease caused by a fungal organism, which is commonly
found in the soil mostly in the Midwestern United States.
There are two basic types of histoplasmosis, systemic and
ocular. Systemic histoplasmosis produces an influenza-like
illness with fever and weakness that usually lasts about
two weeks. After recovery, the infection can leave small,
usually harmless, scars throughout the body. The eye can
be involved and the scars can be detected during an examination
of the retina. Visual problems never develop during the
initial, acute infection.
What
is Ocular Histoplasmosis?
 Most
people with healed “histo” scars in the eye
do not develop further problems. However, abnormal blood
vessels may begin to grow through the healed histoplasmosis
scars many years later. These abnormal blood vessels may
cause bleeding and further scarring which can damage the
retina. If the abnormal blood vessels are near the central
part of the retina (the macula), reading vision may be damaged.
Early diagnosis and treatment of these abnormal blood vessels
is very important. Visual problems from ocular histo can
occur long after the systemic phase.
How
Will I Know if I Am Developing Ocular Histoplasmosis?
Most people with active ocular
histoplasmosis have blurred or distorted vision in one or
both eyes. Distorted vision is a very important symptom
and should be reported promptly to your doctor. This may
appear as straight lines looking wavy (doorways, telephone
poles, flagpoles, etc.). Many people with decreased vision
in one eye may not realize they have a problem because the
remaining good eye compensates so well. It is very important
to check each eye separately. Ocular histoplasmosis may
affect both eyes, although the second eye may not become
involved for many years.
Ocular histoplasmosis is diagnosed with an eye examination
involving dilation of the pupils. A special photograph test,
which is often helpful, is fluorescein angiography. In this
test, dye is injected through an arm vein and pictures are
taken of the eye as the dye circulates through the retina.
These pictures are helpful in diagnosis and also serve as
a road map for possible laser treatment.
What
Treatment Is Available for Ocular Histoplasmosis?
There are no eye drops or antibiotics
known to be effective in ocular histoplasmosis. When abnormal
vessels grow outside of the centermost part of the macula,
laser surgery has the best chance of stopping the progression
of abnormal blood vessels. If the vessels are growing in
the very center, newer laser techniques may help. Sometimes
it is possible to do a delicate operation to reach under
the retina and physically remove them.
What
is Laser Treatment Like?
Laser is a precisely focused
beam of light, which can seal (cauterize) tissue in the
retina. The laser beam seals abnormal vessels but does not
help already damaged retinal tissue to function better.
If some of the visual decrease is due to swelling from leaky
blood vessels rather than scar tissue per se, then laser
may actually help vision by allowing the swelling to subside.
Laser surgery is done in the office and is not painful.
After the treatment, you will be free to return home. Unfortunately,
laser surgery does not always eliminate abnormal blood vessels.
In some cases, additional treatment may be needed. Even
if vision is not improved, laser therapy may help to limit
visual loss and minimize damage that would have occurred
without treatment.
Can
I Prevent Ocular Histoplasmosis?
The factors that cause active
histo are poorly understood at this time. The body's immune
system may play a role. No special diet or medical treatment
has been shown to prevent the formation of abnormal blood
vessels. If you have macular histo scars, you should monitor
your vision at home with an “Amsler Grid”, or
a piece of graph paper and report any sign of distortion
or decreased vision to your doctor promptly. Remember, the
earlier the diagnosis is made, the better the chance of
saving the reading vision. Laser treatment for histo scars
that are not active has not been shown to be effective.
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