Presumed Ocular Histoplasmosis Syndrome (POHS)

Histoplasmosis is caused by a fungus that can make you sick if you inhale it. In some people, the fungus spreads to the eyes. When this happens, abnormal blood vessels form, which can affect your vision. Without treatment, vision loss can become permanent.


What is histoplasmosis?

Histoplasmosis occurs when the fungus Histoplasma capsulatum infects the lungs. Histoplasma capsulatum is in soil with high levels of bird or bat droppings (poop). It’s more common in the central U.S., in the states that make up the Ohio and Mississippi River valleys.


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What is presumed ocular histoplasmosis syndrome (POHS)?

POHS is an eye condition that’s a complication of histoplasmosis. It happens when the disease travels through the bloodstream to the back of the eyes.

How can ocular histoplasmosis affect me?

Many people breathe in Histoplasma capsulatum and do not get sick. But, if it reaches the eyes, it can cause:

  • Abnormal blood vessels (choroidal neovascularization) that can affect eye functioning.
  • Scarring.


Who is most likely to get POHS?

You face a higher risk of this condition if you:

  • Live in the Ohio or Mississippi River valleys.
  • Handle birds, like chickens.
  • Work on a farm or construction site with contaminated soil.
  • Currently use or have a history of using tobacco.

Another risk factor is having a weakened immune system, which can occur:

Symptoms and Causes

What causes ocular histoplasmosis?

When Histoplasma capsulatum is in the soil, plowing a field or digging a hole stirs up the fungus. It also happens if you spend time in or near a chicken coop. These activities make it possible to breathe in the fungus and get a lung infection. Researchers aren’t sure how it travels from the lungs to the back of the eyes.


What are ocular histoplasmosis symptoms?

The condition does not cause symptoms in the early stages. If Histoplasma capsulatum affects the eyes, choroidal neovascularization can occur, affecting your vision.

You may notice:

  • An object’s size appears different in each eye.
  • Blind spots.
  • Blurred vision or painless vision loss.
  • Colors don’t appear as they should (may be dull).
  • Flashes or flickering.
  • Lines that should be straight, like lane markers on the road, appear wavy.

Diagnosis and Tests

How is POHS diagnosed?

The first step is an evaluation from an eye doctor (ophthalmologist). They examine the back of the eye for:

  • Scar tissue.
  • Swelling.

What happens if I have signs of ocular histoplasmosis syndrome?

You will need a dilated eye exam to assess histoplasmosis symptoms in greater detail. The ophthalmologist uses eye drops to expand (dilate) your pupils, the black center of the eye. Dilation makes it possible to perform a more thorough evaluation and check for:

  • Abnormal blood vessels.
  • Fluid.
  • Inflammation.
  • Small white spots.

Your care may also include a fluorescein angiography. The procedure starts by injecting a special dye into a vein. The dye travels through the bloodstream to reach the blood vessels in your eye. A special camera takes pictures, making it possible to detect choroidal neovascularization.

Management and Treatment

Who needs histoplasmosis treatment?

Not everyone needs treatment. If Histoplasma capsulatum is not affecting your vision, you may only need monitoring.

What does ocular histoplasmosis treatment look like?

Your care will likely not include antifungal medications. Even though a fungus causes ocular histoplasmosis, it’s not the same as having a fungal infection.

Instead, your care may include therapies to stop choroidal neovascularization, such as:

  • Antivascular endothelial growth factor (anti-VEGF) therapy: You receive injections of anti-VEGF in the affected eye. This substance blocks abnormal blood vessel development, which can relieve symptoms. It may take several injections before you notice results.
  • Photodynamic therapy: You receive an injection of a light-sensitive drug (verteporfin) into your arm. It accumulates in the abnormal blood vessels in the eye. Low-power laser beams activate the drug to destroy the abnormal blood vessels.


How can I prevent POHS?

You can’t see Histoplasma capsulatum when it’s in the air, making it impossible to avoid breathing it in. If you have histoplasmosis risk factors, you should avoid certain activities.

These include:

  • Exploring caves because they have bat poop and poor air circulation.
  • Going in or near chicken coops.
  • Working with soil that may have bird or bat poop in it.

What else can I do to protect myself?

If you have Histoplasma capsulatum in your lungs, you might not be able to prevent it from spreading to your eyes. Regular monitoring can catch early signs of eye problems.

Outlook / Prognosis

What is the prognosis for people with ocular histoplasmosis?

Ocular histoplasmosis treatment can prevent further vision loss. But some people do not regain full vision.

How can POHS affect my future health?

Even if histoplasmosis treatment is successful, ocular histoplasmosis symptoms can come back. If you do get it again, you may experience less severe symptoms. People with weakened immune systems are more likely to experience recurrence.

Living With

What’s it like living with ocular histoplasmosis syndrome?

If you have ongoing vision problems, you may benefit from low vision rehabilitation. A therapist teaches you methods for safely navigating everyday life. Suggestions may include eliminating tripping hazards in your home.

A note from Cleveland Clinic

POHS occurs when the fungus Histoplasma capsulatum affects the eyes. This condition is more common in the central U.S. in areas where the soil has high levels of bird and bat poop. If you are at risk, regular check-ups enable healthcare providers to detect early histoplasmosis symptoms. In people who test positive, timely ocular histoplasmosis treatment can help you avoid permanent vision changes.

Medically Reviewed

Last reviewed on 08/09/2021.

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