Presumed Ocular Histoplasmosis Syndrome (POHS)

Presumed ocular histoplasmosis syndrome (POHS) is a rare eye condition that’s a complication of having histoplasmosis.

Histoplasmosis is a fungal infection that usually affects your lungs. POHS happens when you’re exposed to the fungus that causes histoplasmosis, which causes changes and scarring in your retinas.

Damage from the fungus can make abnormal blood vessels form in your retinas (choroidal neovascularization). This can lead to scarring that causes permanent damage and vision loss if it’s not treated.

Symptoms of POHS

POHS doesn’t cause symptoms in the early stages. You won’t notice any changes in your eyes or vision until choroidal neovascularization happens.

You may notice:

• An object’s size appears different in each eye
• Blind spots, especially in the center of your vision
• Blurred vision or painless vision loss
• Colors seem duller than usual
• Flashes or flickering (photopsia)
• Lines that should look straight (like lane markers on the road) may appear wavy or crooked (distorted vision)

POHS causes

The Histoplasma capsulatum fungus causes POHS when it spreads to your retinas. Histoplasmosis happens when you breathe in the fungus. It usually lives in soil. Plowing a field or digging a hole can stir it into the air. Spending time around birds (especially chickens) or bats can expose you to the fungus. These animals can have it in their bodies and spread it through their poop.

Breathing in Histoplasma capsulatum can cause a lung infection. Researchers aren’t sure why some people who’ve had histoplasmosis later develop POHS. But it’s not from an active fungal infection in your eye. Most people exposed to Histoplasma never develop POHS. But it can show up decades after you had a lung infection.

POHS isn’t contagious. You can’t spread it to other people.

Risk factors for ocular histoplasmosis

Histoplasma capsulatum is found in soil with high levels of bird or bat poop. It’s more common in the central U.S., in the states that make up the Ohio and Mississippi River valleys.

You have a higher risk of histoplasmosis and POHS if you:

• Live in places where Histoplasma capsulatum is common
• Handle birds (especially chickens)
• Work on a farm or construction site with contaminated soil
• Currently use or have a history of smoking or using other forms of tobacco
• Have a condition or take a medication that causes a weakened immune system

POHS complications

POHS can cause permanent vision loss if it isn’t treated right away. Visit an eye doctor or healthcare provider as soon as you notice any changes in your vision, even if they seem minor. That’s especially true if you know you’ve had histoplasmosis or any POHS risk factors.

How doctors diagnose ocular histoplasmosis

An eye care specialist will diagnose POHS using a combination of an eye exam and asking about your life and medical history. They’ll use eye dilation and a slit lamp exam to look for changes and damage in your retinas.

Other tests that can help diagnose POHS include:

• Fluorescein angiography
• Optical coherence tomography (OCT)
• Fundus autofluorescence (an imaging test that doesn’t use dye to highlight parts of your eye)

Your eye doctor may also recommend lab tests to rule out other conditions that can cause retinal scars and similar symptoms.

Treatment for histoplasmosis in the eye

You’ll only need treatment for POHS if you’re experiencing symptoms that affect your vision. If you need treatment, your eye doctor will suggest ways to stop choroidal neovascularization, including:

• Antivascular endothelial growth factor (anti-VEGF) therapy: Anti-VEGF is the best and most common POHS treatment. Your provider will inject anti-VEGF into your affected eye. This medication blocks abnormal blood vessel development. This can relieve symptoms. It may take several injections before you notice results.
• Photodynamic therapy: This is an injection of a light-sensitive drug (verteporfin) into your arm. It accumulates in the abnormal blood vessels in the eye. Your provider will activate the drug with a low-power laser. After activation, the drug destroys the abnormal blood vessels.
• Laser photocoagulation: This procedure involves zapping newly formed blood vessels with a safe, specially tuned laser. The laser destroys the new blood vessels, keeping them from growing and causing more damage. This procedure is rare. Your eye doctor will usually only suggest it if the abnormal blood vessels don’t affect the center of your retina.

You won’t need antifungal medications to treat POHS. Your healthcare provider may prescribe an antifungal to treat a histoplasmosis infection in your lungs if you have an infection. But these medications can’t treat or reverse the abnormal blood vessels in your retinas that happen with POHS.

When should I see my healthcare provider?

Visit a healthcare provider or eye doctor as soon as you notice any changes in your eyes or vision. Tell them if you know you have histoplasmosis and when it was diagnosed.

Trust your intuition. You know when something isn’t right or normal for you, especially when it comes to your vision. The sooner you get POHS diagnosed, the better your chances of preventing neovascularization and vision loss.

What can I expect if I have POHS?

You might regain your full vision if you get POHS diagnosed and treated right away. But you might have some permanent vision loss.

Some people experience neovascularization again in the future, even after treatment. It can even happen years later. Talk to your eye doctor about your risk of it coming back.

If you have permanent vision loss, you may benefit from low vision rehab. A therapist will help you find the right kinds of vision aids and modify activities to help you stay safe during your daily routine.