Ocular histoplasmosis can result from the lung infection histoplasmosis. (Learn More) Doctors believe that even when the initial infection is mild, it can move to the eyes via the bloodstream.

In the U.S., among adults ages 20 to 40, ocular histoplasmosis is one of the top causes of vision loss.

Avoiding a histoplasmosis infection is the best defense against ocular histoplasmosis syndrome. (Learn More) Proper precautions can be used to minimize the risk of catching the initial infection.

If the fungus gets into the eye, it lodges in the choroid structure of the eye. (Learn More) It is important that all people know about this syndrome since it can have profound affects on eye health. Knowing the symptoms is the first step to prevent long-term issues.

If this condition is suspected, prompt diagnosis is essential. (Learn More) There is one proven treatment doctors can use, known as photocoagulation. (Learn More)

What Is Histoplasmosis?

Histoplasmosis is an infection that affects the lungs. It is caused by fungal spores known as Histoplasma capsulatum. People contract this infection when they inhale the spores.

Not all people who inhale the spores develop an infection. Many people recover from the infection without medical intervention. There are cases where it becomes severe, especially among people with weak immune systems.

The spores float in the air since they are light. They generally start in the soil and can get into the air when the soil is disturbed.

This fungus is common in environments that have soil with a lot of organic matter. Bat and bird droppings in the soil increase the risk for this fungus being present.

This infection is not contagious.

The symptoms of infection include the following:

  • Chills
  • Muscle aches
  • Chest discomfort
  • Fever
  • Headache
  • Dry cough

In the mildest cases, people might not have any symptoms. When symptoms present, they generally begin 3 to 17 days after a person has been exposed to the fungal spores.

In the most severe cases, a form of this infection known as disseminated histoplasmosis is possible. Without treatment, this form of the infection can be fatal.

Histoplasmosis Causes and Risk Factors

2 farmers

People who are regularly in certain environments are at a higher risk for developing this infection. This is because the fungal spores are found more often in specific places.

People who work in the following professions are at a higher risk for histoplasmosis:

  • Farm employees
  • Poultry keepers
  • Roofing professionals
  • Cave explorers
  • Pest control workers
  • Construction workers
  • Gardeners and landscapers

When people are in this type of environment, they should wear a mask to reduce their risk of inhaling the spores. Once leaving these environments, they should shower or bathe to remove any spores that may be sticking to their body or clothing.

Ocular Histoplasmosis Syndrome

It is believed that once someone inhales the spores, they can travel to the eyes via the bloodstream. Once in the eye, they lodge into the choroid structure. This part of the eye is responsible for providing nutrients and blood to the retina.

This syndrome is characterized by abnormal, fragile blood vessels developing below the retina. These form a choroidal neovascularization lesion. Vision loss can occur when these lesions start to leak.

If this condition goes untreated, normal retinal tissue can be replaced by scar tissue in the macula. The result is that central vision is negatively impacted since visual messages that go from the retina to the brain are interrupted. This is what results in vision loss.

If the abnormal blood vessels continue to grow and start to affect the fovea of the eye, the cones in this structure can become impaired. This can lead to the severe impairment or destruction of straight-ahead vision.

Once the abnormal blood vessels affect this fovea, control of the disease is considerably more difficult. While this condition can severely impact a person’s vision, it does not result in complete blindness, and it rarely impacts peripheral vision.

This syndrome is relatively rare. Few people who have histoplasmosis go onto to develop ocular histoplasmosis syndrome.

Anyone who has lived in a state where histoplasmosis is common should talk to their eye doctor about getting an examination to see if “histo spots” are present. These states include:

  • Arkansas
  • Missouri
  • West Virginia
  • Illinois
  • Iowa
  • Louisiana
  • Mississippi
  • Ohio
  • Texas
  • Kentucky
  • Tennessee
  • Alabama
  • Indiana
  • Kansas
  • Maryland
  • Nebraska
  • Oklahoma
  • Virginia

In the early stages, people often do not have any symptoms of this syndrome. The initial infection may go away on its own.

It is not well understood why some people develop serious vision complications and others do not. For many people, the symptoms do not occur until the abnormal blood vessels start to develop.

An opthamologist is listening to the patient in an exam room.

Diagnosing Ocular Histoplasmosis

When someone goes to a doctor and ocular histoplasmosis syndrome is suspected, the doctor is usually looking for two things:

  • The retina is swollen due to abnormal blood vessels growing.
  • Histo spots are present, showing that the person was once exposed to the fungal spores.

The doctor will perform a dilated eye examination to confirm the diagnosis. This exam allows the doctor to look at the retina better. Special eyedrops are used to temporarily increase the size of the pupils.

If the doctor observes abnormal blood vessels, they may recommend a fluorescein angiography. This procedure allows the doctor to see a CNV lesion since it makes it easy to examine the back of the eye.

It also gives them a chance to document the extent of the spread and the location of the lesion. The doctor will work to determine how close the vessels are getting to the fovea.

Ocular Histoplasmosis Treatment

Once the doctor has made a definitive diagnosis, treatment options can be discussed.

Photocoagulation, a type of laser surgery, is the only proven treatment for this condition. The purpose of the surgery is to destroy any abnormal structures that are present in the retina. In the case of ocular histoplasmosis, it is used to destroy the abnormal blood vessels.

The doctor will usually use one of three patterns to apply the laser spots. The laser will target the affected tissue and create a microscopic burn.

Prior to surgery, people will have their pupils dilated. While it is not common, some doctors will administer a local anesthetic. During the procedure, the patient remains awake, and they do not experience pain.

The patient has their head positioned for the surgery. The doctor then takes the laser and aims it at the affected area. A flash of light is visible when the laser pulses. How many pulses are used will depend on the severity of the condition.

In most cases, there are no special preparations that patients have to do before the procedure. Just expect the eyes to be dilated.

Patients should ensure they have someone who can drive them home. They usually go home right after the procedure.

For the first 24 hours after surgery, it is possible to have blurry vision. People can also experience floaters temporarily.

Both of these issues typically resolve on their own. If they become worse, the doctor should be contacted right away.

Like all surgical procedures, there are some risks with photocoagulation that people should know about.

  • Mild loss of vision
  • Blind spots
  • Difficulty focusing
  • Reduced color vision
  • Reduced night vision
  • Reduced side vision
  • Blurry vision

perspective of someone with blurry vision

Following all preparation instructions will help to reduce these risks. Patients should be aware of potential complications and report them to their doctor right away if they occur.

Follow all recovery instructions, and take all prescribed medications exactly as directed. It is also important to rest for as long as the doctor recommends.

Preventing Histoplasmosis

Preventing the initial histoplasmosis infection is the primary goal. Ocular histoplasmosis syndrome cannot occur unless someone has a histoplasmosis infection.

The following are recommended preventative measures:

  • Avoid areas where the fungus is common whenever possible.
  • Use a face mask that can effectively prevent inhalation of the spores.
  • Use proper cleaners to spray surfaces before cleaning the area to decrease the risk.

Anyone who suspects a histoplasmosis infection should see their doctor right away. Not all infections are serious, but it becomes serious if it gets into the eyes.

Prompt treatment may help to reduce the risk of this infection leading to ocular histoplasmosis syndrome.

References

What Is Histoplasmosis? American Academy of Ophthalmology.

Histoplasmosis. Centers for Disease Control and Prevention.

Histoplasmosis. Mayo Clinic.

Choroid. ScienceDirect.

What Are Choroidal Neovascular Membranes? American Academy of Ophthalmology.

The Dilated Eye Exam: Why It’s So Important. Bright Focus Foundation.

Fluorescein Angiography. Healthline.

Laser Photocoagulation – Eye. AMITA Health.