Ocular Histoplasmosis
Definition
Ocular histoplasmosis is an eye disorder that can
lead to permanent loss of central vision to a variable degree
in one or both eyes. Histoplasmosis is thought to occur as a result
of a previous infection from the fungus Histoplasma capsulatum
causing residual scars in the back of the eye. The infection gains
access to the body through the lungs and enters the bloodstream
where the fungus spreads to different body organs, including the
eye.
Occurrence
The highest prevalence of this fungus in the world
occurs in the United States along the Mississippi and Ohio River
valleys. The fungus is so common in these regions that, indeed,
in some areas, 80% of children five years of age will have positive
laboratory evidence of having been infected. Over 99% of these
infections do not cause symptoms. If symptoms do occur, they are
typical of those that occur with influenza, that is, fever and
fatigue. The infection lasts two days to two weeks, and resolves
usually without any eye symptoms during this initial infection.
Ocular Symptoms
Distorted vision –
Straight lines or objects may appear wavy.
Blurred vision –
The central vision may be blurred while the peripheral, or side,
vision remains unchanged.
Like most retinal conditions, there is no discomfort.
Diagnosis and Risk
An ophthalmologist, by examining the back of the
eye (the retina), may detect scar tissue, which is indicative
of a previous infection. If these scars are present in or near
the macula, the patient is at risk for possible visual loss. The
macula is that portion of the retina responsible for our central
vision, which enables us to see fine detail for tasks such as
reading. These scars may remain inactive for one’s entire
life, or they may become active many years later, producing visual
symptoms.
Activation of scar tissue does not actually represent
a new infection but rather is a result of the initial infection.
For reasons that are not fully understood, new abnormal blood
vessels can develop in the choroid, the vascular layer underlying
the retina. This process is called choroidal neovascularization.
These new vessels can leak fluid or bleed and cause symptoms such
as blurred or distorted vision. If this occurs in the center of
the macula, the result may be permanent loss of central vision.
The presence of these new blood vessels can often
be confirmed by performing a fluorescein angiogram. This is a
test in which fluorescein dye is injected into a vein in the arm
while photographs are taken of the retina choroid in the back
of the eye as the dye passes through the blood vessels in these
layers. In most cases, this allows the ophthalmologist to identify
these new blood vessels.
Treatment
No treatment is necessary or possible for the inactive
scars, which occur as a result of the primary infection. However,
the new blood vessels that may arise later from these scars may
be treated with laser, or with surgery in very specific circumstances.
Laser treatment or surgery will not prevent recurrence of these
new blood vessels, and therefore, even if treatment is successful,
the patient should continue to have regular eye exams indefinitely.
If you have any comments or questions feel free
to email us or call 920-327-7000 or 1-877-462-9465 |
Quick Links
Click the links below to learn more about some of the conditions
Green Bay Eye Clinic physicians specialize in.
Cataracts
Blepharoplasty
Glaucoma
Extraocular Muscles
Retinopathy of Prematurity (ROP)
Retinal Detachment
Ocular Histoplasmosis
If there is a condition not listed here that you would like to be consulted about, contact
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