Ocular Histoplasmosis Syndrome (OHS)
A result of inhaling dust that carries fungal spores
Histoplasmosis is contracted by inhaling dust that carries fungal spores. Its effects on the body can vary widely in severity from one person to another. The fungus may affect the eye by causing small areas of inflammation and scarring of the retina. These are called “histo spots” and may be found in both eyes. Their affect on vision depends on the location of the scars. Scarring in the peripheral area of the retina may have little or no impact on vision, while a central scar affecting the macula may cause a prominent blind spot.
Studies suggest that the histoplasmosis spores are inhaled and travel from the lungs to the eye. OHS develops when abnormal blood vessels grow under the retina. The abnormal blood vessels form a lesion, choroidal neovascularization (CNV), which can turn into scar tissue and replace the normal retinal tissue if left untreated.
Most people with OHS test positive for exposure to the fungus, histoplasma capsulatum. In the United States' east coast and central states, 90 percent of adults have been exposed to histoplasma capsulatum. This fungus is in molds from soil with bat, chicken or starling droppings and yeasts from animals.
Histoplasmosis is usually mistaken for a cold, and overcome by the body's immune system in a few days.
Treatment for OHS can range from intravitreal medications (Anti-VEGF compounds), laser surgery called photocoagulation or retinal surgery called pars plana vitrectomy. Treatment is only necessary if the new vessels are in the macula, the part of the retina responsible for fine detail vision.