R R

What Is Ocular Histoplasmosis Syndrome (OHS)?

Ocular histoplasmosis syndrome (OHS) is a retinal condition associated with previous infection by Histoplasma capsulatum, a fungus found in certain river valley regions. People with OHS classically have a triad of peripapillary atrophy, small punched out chorioretinal scars called histo spots, and a predisposition to choroidal neovascular membranes in the macula. Active fungus is not usually present in the eye at the time of diagnosis. The main threat to vision comes from abnormal new vessels that grow under the retina and leak or bleed.

Link to This Resource Page

Provide a valuable resource to your clients or customers by linking to this resource page. Just place the following link on your website.

To display this...

What Is Ocular Histoplasmosis Syndrome (OHS)?

Ocular histoplasmosis syndrome (OHS) is a retinal condition associated with previous infection by Histoplasma capsulatum, a fungus found in certain river valley regions. People with OHS classically have a triad of peripapillary atrophy, small punched out chorioretinal scars called histo spots, and a predisposition to choroidal neovascular membranes in the macula. Active fungus is not usually present in the eye at the time of diagnosis. The main threat to vision comes from abnormal new vessels that grow under the retina and leak or bleed.

read more about ocular histoplasmosis syndrome ohs ...

Copy this HTML:

Copy HTML Copied!

Clinical Features and Risk Regions

Many individuals with OHS lesions have no symptoms and are found incidentally during routine exams. When choroidal neovascularization develops, patients notice blurred central vision, distortion of straight lines, or a dark spot near the center of vision. OHS is strongly associated with residence in areas where histoplasmosis is common, such as the Ohio and Mississippi River valleys. Fundus examination shows peripapillary atrophy, scattered histo spots in the midperiphery, and, when present, a subretinal neovascular complex in the macula.

Pathophysiology and Disease Mechanism

The leading theory is that inhaled histoplasma spores cause a primary lung infection and then spread hematogenously to the choroid, leaving small scars after the immune system clears active infection. Years later, weakness at these scar sites and changes in Bruch's membrane can promote choroidal neovascularization. Not everyone with histo spots develops neovascular membranes, so additional genetic or environmental factors are suspected. Smoking has been identified as a risk factor for neovascular complications in some studies.

Diagnosis and Imaging

Diagnosis is based on the characteristic fundus triad and the presence or absence of choroidal neovascularization. Fluorescein angiography helps identify leaking neovascular membranes and defines their size and location. Optical coherence tomography is used to visualize subretinal fluid, pigment epithelial detachments, and retinal thickness. Serologic tests for histoplasma exposure are not always needed when the eye picture is typical. Other causes of chorioretinal scars and macular neovascularization must be considered in atypical cases.

Treatment and Prognosis

When choroidal neovascularization is present, intravitreal anti–VEGF injections are the main treatment to reduce leakage and stabilize or improve vision. Older approaches such as laser photocoagulation or photodynamic therapy are used less often. Patients without neovascular membranes are monitored periodically for new symptoms or changes on self testing with an Amsler grid. Prognosis depends on the location and extent of macular involvement and on how early treatment begins. Many eyes maintain useful vision with timely therapy, but recurrent episodes can cause permanent central scarring.

FAQs About Ocular Histoplasmosis Syndrome

Can I catch histoplasmosis from someone with OHS?

No, OHS reflects past exposure to histoplasma and is not contagious between people.

Will I always develop macular problems if I have histo spots?

No, many people with scars never develop neovascular membranes, though regular monitoring is advised.

Are steroid eye drops helpful for OHS?

Steroids do not treat the neovascular process; anti–VEGF injections are the standard for active membranes.

Should I move away from an endemic area after diagnosis?

Moving does not change existing eye scars, but avoiding heavy exposure to dust in endemic regions can reduce systemic risk.

References

EyeWiki. ?Presumed Ocular Histoplasmosis Syndrome.? https://eyewiki.org/Presumed_Ocular_Histoplasmosis_Syndrome

American Academy of Ophthalmology (AAO) EyeNet. ?Management of Presumed Ocular Histoplasmosis Syndrome.? https://www.aao.org/eyenet/article/management-presumed-ocular-histoplasmosis-syndrome

Centers for Disease Control and Prevention (CDC). ?Histoplasmosis.? https://www.cdc.gov/fungal/diseases/histoplasmosis/index.html

American Society of Retina Specialists (ASRS). ?Presumed Ocular Histoplasmosis Syndrome.? https://www.asrs.org/patients/retinal-diseases/19/presumed-ocular-histoplasmosis-syndrome

MSD Manual (Consumer). ?Ocular Histoplasmosis Syndrome.? https://www.msdmanuals.com/home/eye-disorders/retina-disorders/ocular-histoplasmosis-syndrome