Presumed Ocular Histoplasmosis Syndrome (POHS)

POHS is most common in states along the Ohio and Mississippi River valleys, where Histoplasma capsulatum thrives in moist soil. People who have lived in or traveled through these regions are more likely to have been exposed to the fungus, sometimes without any memory of illness.

Vision-threatening complications from POHS most often appear between a person's 20s and 50s, making it one of the few serious retinal conditions that primarily affects younger and middle-aged adults.

Not everyone who has histo spots will develop the abnormal blood vessels that threaten vision. However, several factors increase that risk and are worth discussing with your eye care provider.

• Smoking is the most significant risk factor, with smokers facing nearly three times the odds of developing CNV compared to nonsmokers
• Increasing age raises the likelihood of CNV forming at the sites of existing histo spots
• Rural residence has been independently linked to POHS development
• Diabetes may also be associated with POHS in some patients

Smoking deserves special attention because it is the strongest modifiable risk factor for developing CNV in POHS. Quitting smoking is one of the most meaningful steps a person with histo spots can take to reduce the chance of sight-threatening complications.

If you have been diagnosed with POHS or have lived in an area where the fungus is common, speak with your primary care provider about smoking cessation support. This single change can make a real difference in protecting your long-term vision.

Anti-VEGF (vascular endothelial growth factor) therapy is the primary treatment for CNV caused by POHS. These medications block the chemical signals that drive abnormal blood vessel growth and leakage. They are delivered as intravitreal injections, meaning the medication is injected directly into the vitreous, the gel-like interior of the eye, using a very fine needle.

Commonly used anti-VEGF medications for POHS-related CNV include aflibercept (Eylea), ranibizumab (Lucentis), and bevacizumab (Avastin). It is worth knowing that no anti-VEGF agent is currently FDA-approved specifically for POHS, but these medications are widely used and supported by clinical evidence for this condition.

The HANDLE study examined different dosing schedules for intravitreal aflibercept in patients with POHS-related CNV. At twelve months, researchers found no meaningful difference in visual or anatomic outcomes between patients on a fixed dosing schedule and those treated on an as-needed basis.

These findings suggest that individualized, as-needed treatment may be a reasonable approach for some patients, potentially reducing the total number of injections while maintaining good outcomes. Your retina specialist will recommend a schedule based on how your eye responds.

Photodynamic therapy (PDT) is a light-activated treatment that has received FDA approval specifically for CNV in POHS. A light-sensitive medication called verteporfin is injected into a vein, and then a low-energy laser is directed at the abnormal blood vessels in the eye. The laser activates the drug and seals the vessels.

PDT was the standard treatment for POHS before anti-VEGF therapy became available. It may still be used in certain cases, sometimes alongside anti-VEGF injections, depending on how a patient responds.

If a retina specialist finds histo spots or peripapillary atrophy but no evidence of CNV, treatment is typically not needed. The recommended approach is regular dilated eye exams combined with daily at-home monitoring using an Amsler grid.

The goal is to detect any new blood vessel growth as early as possible so that treatment can begin before significant vision loss occurs. Careful observation is an active and important part of managing POHS.

There is no proven way to prevent POHS if you have been exposed to Histoplasma capsulatum. Most people who breathe in the spores never experience noticeable illness, and the exposure typically happens during childhood before anyone knows to take precautions. The most effective strategy is awareness. Regular dilated eye exams allow a retina specialist to find histo spots early, before any complication develops. Avoiding smoking significantly lowers the risk of CNV, which is the most serious outcome of POHS.

Not necessarily, and many patients do not. Treatment duration varies considerably from person to person. Some patients respond well to an initial course of anti-VEGF injections and can eventually stop, with continued monitoring to watch for recurrence. Others may need periodic injections if CNV returns. The HANDLE study showed that an as-needed approach can produce outcomes comparable to more frequent fixed dosing, which may reduce the overall number of treatments required. Your retina specialist will adjust your plan based on how your eye responds over time.

No, they are distinct conditions despite some surface similarities. Both can involve CNV and threaten central vision, but their causes and typical patient profiles differ. POHS is linked to a prior fungal exposure and most often affects adults between their 20s and 50s. Age-related macular degeneration is a degenerative condition that primarily develops after age 50 and is not connected to any infectious cause. While both conditions may be treated with anti-VEGF injections, the underlying disease processes are entirely different, and so is the long-term management approach.

Yes. Because the fungus spreads through the bloodstream during the original infection, histo spots can be present in both eyes even if only one eye has ever caused symptoms. Vision-threatening CNV does not necessarily develop in both eyes at the same time, and it may appear in one eye years before affecting the other. For this reason, a retina specialist will examine both eyes carefully at every follow-up visit, even if one eye has always been asymptomatic.

POHS primarily affects central vision, which is used for reading, recognizing faces, and other detail-focused tasks. Peripheral vision is generally preserved, even when CNV causes damage to the macula. With prompt detection and modern anti-VEGF therapy, many patients retain functional central vision. Complete blindness from POHS is uncommon, but delaying treatment when CNV is active can lead to significant and lasting central vision loss. This is why any new symptom should be evaluated without delay, rather than monitored at home to see if it resolves.

The right monitoring schedule depends on your individual situation, including your history of symptoms, whether CNV has occurred before, and your risk factors such as smoking status. A retina specialist will determine how frequently you should be seen based on those factors. As a general principle, any person with known histo spots should never skip a scheduled exam, even when vision feels completely normal. Changes can develop quickly, and catching them early is far more effective than treating advanced disease.