Ocular Histoplasmosis Syndrome (OHS)

What is Ocular Histoplasmosis Syndrome (OHS)

Ocular histoplasmosis syndrome occurs when a certain type of fungal infection spreads from the lungs to the eye or eyes through the bloodstream.

The infection damages the blood vessels that supply the light-sensitive layer in the back of the eye (retina). This can lead to vision loss.

OHS does not cause complete blindness, but it damages your vision. This damage cannot be reversed. However, early diagnosis and treatment can prevent the condition from getting worse.

What are the causes?

This condition is caused by the Histoplasma capsulatum fungus. This fungus is found all over the world, but it is more common in some areas of the United States. It builds up in the soil and in areas with a lot of bird droppings. When these spores are released into the air and inhaled by a person, the person can get a histoplasmosis infection in the lungs. In rare cases, the infection can spread to the eyes, causing OHS.

What increases the risk?

You are more likely to develop this condition if:

  • You have ever had a histoplasmosis lung infection.
  • You smoke.
  • You live in certain areas of the United States, including areas near the Mississippi and Ohio Rivers and parts of the mid-Atlantic region.

What are the signs or symptoms?

A sudden, painless change in vision is the most common symptom of OHS. Visual changes may occur years after a lung infection. Visual changes may include:

  • Seeing straight lines as wavy or crooked.
  • Having dim vision or blind spots (scotoma).
  • Losing the ability to see straight ahead (central vision).
  • Things appearing smaller than they are (micropsia).

How is this diagnosed?

Your health care provider may suspect OHS if:

  • You have changes in vision and have been diagnosed with histoplasmosis in the past.
  • You live in an area where histoplasmosis is common.

You may have to see an eye specialist (ophthalmologist) to get an OHS diagnosis. The ophthalmologist may:

  • Do an eye exam using a scope to check for scars (histo spots) on your retina. Before checking your retinas, the ophthalmologist may put drops in your eyes to make your pupils bigger.
  • Do a test called a fluorescein angiogram. In this test, a type of dye is injected into a vein in your arm. This dye travels to your eyes and makes the blood vessels there more visible.

You may also need a chest X-ray to check for signs of lung infection.

How is this treated?

The goal of treatment is to prevent more vision loss. This condition may be treated with:

  • Laser surgery (photocoagulation). In this procedure, a powerful beam of light energy is used to destroy the abnormal blood vessels in the retina. This prevents them from growing into the most sensitive central area of the retina. This procedure is the most effective way to treat the condition.
  • Vision aids. These are used if you already have vision loss. Your health care provider can provide you with the devices you need and show you how to use them.

Follow these instructions at home:

  • Check your eyes daily for vision changes if directed to do so by your health care provider.
    • You can do these eye checkups at home with a tool called an Amsler grid.
    • Your health care provider may give you a grid and show you how to use it if necessary.
  • Continue to work closely with all your health care providers. Even after treatment, OHS can come back in the same eye or in the other eye.
  • Use vision aids as directed by your health care provider.
  • Do not drive if you have vision loss and your health care provider tells you not to.
  • Keep all follow-up visits as told by your health care provider. This is important.

Contact a health care provider if:

  • You notice any changes in your vision.
  • You have any changes in the results of your daily eye testing at home.

Summary

  • Ocular histoplasmosis syndrome (OHS) occurs when a certain type of fungal infection spreads from the lungs to the eye through the bloodstream.
  • The infection damages the blood vessels that supply the light-sensitive layer in the back of the eye (retina). This can lead to vision loss.
  • Early diagnosis and treatment can prevent the damage from getting worse.
  • This condition can be treated with laser surgery and vision aids.
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