Ocular Histoplasmosis Syndrome (OHS)

What is OHS?

Ocular histoplasmosis syndrome (OHS) is an eye disorder that may arise in individuals who have contracted a lung infection known as histoplasmosis. If you are affected by histoplasmosis, the infection has the potential to spread from the lungs to the eyes, which can result in a loss of vision.

Many individuals with histoplasmosis are unaware of their condition. If you reside in regions where histoplasmosis is prevalent, such as near the Ohio and Mississippi River Valleys, it is advisable to consult your eye care professional about undergoing an examination for OHS.

What are the symptoms of OHS?

In its initial stages, OHS typically does not present any noticeable symptoms. However, as time progresses, you might begin to observe:

  • Straight lines appearing distorted or wavy

  • Areas of vision that are missing or obscured

What causes OHS?

The lung infection responsible for OHS, histoplasmosis, occurs when individuals inhale spores from a fungus known as Histoplasma capsulatum. This fungus is commonly found in soil enriched with bird or bat droppings. Spores can become airborne when the soil is disturbed, such as during activities like cleaning a chicken coop or tilling a field.

Experts believe that OHS develops when spores migrate from the lungs to the eyes, potentially resulting in scarring at the back of the eye. While these scars are generally harmless, they can sometimes lead to the growth of abnormal blood vessels in the eye, which may contribute to vision impairment.

Am I at risk for OHS?

Anyone can contract histoplasmosis — and subsequently OHS — if they have visited areas where the histoplasma fungus is present. This fungus is especially prevalent in the central and eastern regions of the United States, particularly around the Ohio and Mississippi River Valleys. In fact, many residents in these areas may have histoplasmosis without even realizing it.

Certain demographics are at an increased risk of having histoplasmosis progress to OHS, including:

  • Individuals with compromised immune systems — such as those living with HIV/AIDS or those on specific medications

  • Infants

  • Adults aged 55 and older

It is important to note that OHS is not contagious — if you have OHS, you cannot transmit it to others.

How will my doctor check for OHS?

To determine whether you have OHS, eye care professionals will conduct a dilated eye examination to assess two key factors:

  • Presence of scars at the back of the eye

  • Swelling in the retina (the light-sensitive tissue layer located at the back of the eye)

If the examination reveals fluid, blood, or abnormal blood vessels, your eye doctor may recommend an optical coherence tomography (OCT) test to evaluate swelling and any irregular blood vessels. Additionally, a test known as fluorescein angiography may be performed, allowing the doctor to capture images of the blood vessels in your retina.

What’s the treatment for OHS?

There are two effective treatment options available for OHS. Both treatments are outpatient procedures, meaning you will not need to stay overnight in a hospital.

  • Injections. Medications referred to as anti-VEGF drugs can help prevent the progression of OHS — and may even enhance vision.

  • Laser surgery. Eye specialists can utilize lasers to prevent abnormal blood vessels caused by OHS from leaking, bleeding, or expanding.

If you are experiencing significant vision loss due to OHS, consider asking your doctor for a referral to a low vision specialist. They can assist you in adapting to your vision loss. Learn more about low vision.