Presumed Ocular Histoplasmosis Syndrome (POHS) can significantly affect your central vision. If you have concerns or symptoms, our retina specialists are here to help you understand and manage your vision health effectively. Schedule an appointment today!
This page provides detailed information on Presumed Ocular Histoplasmosis Syndrome (POHS), covering its overview, causes, diagnosis, treatment options, long-term management, and essential guidance for maintaining vision.
Presumed Ocular Histoplasmosis Syndrome (POHS) affects the retina, the part of your eye that senses light, and can impact your vision. It's strongly associated with prior exposure to a common soil fungus, Histoplasma capsulatum, often found in places like the Ohio and Mississippi River valleys. Catching POHS early matters. Many people don't notice symptoms, but regular monitoring can help prevent vision loss if abnormal blood vessels start to grow.
POHS is a condition where tiny scars called histo spots form in the choroid, a layer beneath the retina, after earlier exposure to the Histoplasma fungus. These scars are believed to result from the body’s immune response after breathing in fungal spores. Most people exposed to the fungus don’t have any eye problems. But in some cases, these scars can sometimes trigger abnormal blood-vessel growth beneath the retina in the choroid, a process called choroidal neovascularization (CNV), which can cause vision issues.
POHS can be subtle in its early stages, making regular eye exams essential for early detection and protection of your central vision.
In the beginning, POHS often causes no symptoms at all. Because histo spots lie in the macula or, more commonly, in the mid-peripheral fundus, they can be missed on a cursory exam; a wide-field view is needed to detect the small punched-out chorioretinal scars. These changes signal previous exposure to the Histoplasma fungus, even if you have never noticed any vision problems.
Over time, POHS may lead to the development of abnormal blood vessels near the macula. These vessels can leak fluid or blood, which can harm your sharp, central vision and cause permanent changes if not treated quickly.
If you experience any of the symptoms mentioned, especially the sudden onset of wavy lines, blurriness, or a new blind spot in your vision, it is critical to seek care right away. The development of CNV can happen quickly, and permanent vision loss can occur if it is not treated. Early detection and intervention are the absolute keys to preserving your central vision and achieving the best possible outcome.
The exact pathway that leads from exposure to Histoplasma capsulatum to POHS is still being researched. However, experts believe that the process begins when you inhale fungal spores, usually in regions where the fungus thrives in soil enriched with bird or bat droppings. For most people, this exposure results in a mild or unnoticed lung infection, but in some cases, the fungus appears to trigger small scars in the retina later on.
These retinal scars or “histo spots” do not cause problems by themselves but can later foster the development of abnormal blood vessels around the retina. This growth, termed choroidal neovascularization, disrupts the normal structure and function of the retina, leading to potential vision loss if left untreated.
Although many people are exposed to Histoplasma capsulatum at some point in life, only a handful develop POHS. Factors that may increase one’s risk include:
Anti-VEGF therapy is the most effective treatment for vision loss caused by Presumed Ocular Histoplasmosis Syndrome (POHS). It targets VEGF, a protein that drives abnormal blood vessel growth beneath the retina. By blocking VEGF, these injections help stop leakage, limit further damage, and can stabilize or even improve vision, especially when started early.
Treatment usually begins with monthly injections, with your response closely monitored by our retina specialists. Follow-up visits are essential to track progress and adjust care as needed.
What to expect during treatment:
Before anti-VEGF became the preferred method, laser photocoagulation was commonly used. This treatment seals leaking blood vessels with a focused laser, helping to prevent further fluid buildup in the retina. Because laser can create permanent blind spots, it is now only considered for abnormal blood vessels that are well away from the macula’s center (extrafoveal CNV), and even then, only in select cases. Anti-VEGF injections are the mainstay of treatment for most cases involving the macula.
Photodynamic therapy is sometimes used as an alternative or add-on treatment. Treatment begins with an intravenous infusion of a light-sensitive drug (verteporfin) over about 10 minutes; the drug concentrates in the abnormal vessels. After the drug is infused, a low-energy laser activates it inside the abnormal vessels, leading to selective occlusion with minimal, though not zero, collateral damage to the surrounding retina. Though used less often today, PDT can be helpful in cases where anti-VEGF treatment alone isn't enough.
Contact our experienced retina specialists to schedule a comprehensive eye exam. With regular check-ups and the latest treatments, we can help preserve your vision and address any concerns related to Presumed Ocular Histoplasmosis Syndrome. Don't wait—your vision is invaluable!
The diagnosis of POHS begins with a thorough, dilated eye examination. Our retina specialist will use special eye drops to widen your pupils, which provides a clear and complete view of the back of your eye, including the retina, macula, and optic nerve. During this exam, our retina specialist will look for the classic triad of POHS signs: the characteristic "punched-out" histo spots, atrophy (or wasting away) of tissue around the optic nerve, and choroidal neovascularization (or its macular scar); vitritis is typically absent but is not part of the triad.
If our retina specialist suspects that active, leaking blood vessels (CNV) are present, the next step is an Optical Coherence Tomography, or OCT, scan. This is a quick, non-invasive imaging test that is performed right in our office. It uses light waves to take high-resolution, cross-sectional pictures of your retina. The OCT allows our retina specialist to see the retina’s layers in microscopic detail, making it possible to detect any fluid, swelling, or abnormal blood vessel growth with incredible precision.
For this test, sodium fluorescein, a synthetic, highly fluorescent dye, is injected into a vein in your arm. As it travels through the bloodstream to the retinal vessels, a rapid sequence of photographs is taken with a specialized fundus camera. The dye highlights any abnormal leakages or neovascular membranes, allowing precise mapping of active CNV and guiding targeted therapy.
Optical Coherence Tomography Angiography (OCTA) is a dye‑free imaging modality that captures motion contrast from moving blood cells to map retinal and choroidal microvasculature in vivo. OCTA allows detection of even small neovascular networks without the need for intravenous dye, making it ideal for frequent monitoring. It can reveal early CNV formation, delineate lesion size and flow characteristics, and track response to anti‑VEGF therapy with micrometer‑level resolution.
For patients diagnosed with POHS, even those without active CNV, home monitoring is essential. We will provide you with an Amsler grid, a simple chart of straight lines with a dot in the center. By looking at this grid with each eye separately every day, you can quickly detect the earliest signs of metamorphopsia (wavy lines) or new blind spots. Catching these changes early and alerting our office immediately can make a significant difference in saving your sight.
Ongoing vigilance is key for protecting your vision, especially if you have a history of histoplasmosis or early signs of POHS.
Scheduling periodic eye exams with our retina specialist helps catch subtle retinal changes before they affect your vision. These routine appointments are essential for early detection and timely intervention.
The Amsler grid is a simple, effective tool you can use at home to watch for any new distortions or blind spots. Checking your vision regularly between office visits makes it easier to spot early warning signs of complications like choroidal neovascularization.
If you notice any changes such as blurred vision, wavy lines, or new dark spots in your central vision, contact our retina specialist right away. Fast action allows for a thorough evaluation and, if necessary, early treatment to protect your sight.
No, POHS is not an active infection. It is a condition that results from a past exposure to Histoplasma capsulatum. The fungus itself is not actively infecting the eye; instead, it is the scarring from the previous exposure that may eventually lead to complications in vision.
In most cases, exposure to Histoplasma capsulatum does not result in POHS. Many people inhale the fungal spores during their lifetime without ever experiencing symptoms or changes in their eye health. POHS tends to develop only in a small percentage of individuals who have a certain predisposition or additional risk factors.
Vision changes related to POHS can occur either gradually or suddenly, particularly if choroidal neovascularization develops. While many patients do not notice any changes initially, any sudden appearance of blurred or distorted vision should be addressed immediately by our retina specialists for a thorough evaluation.
Since Histoplasma capsulatum is present in the environment, it is difficult to avoid exposure completely. However, if you know that you are at risk, especially if you live in high-prevalence areas, it is important to be mindful of activities that may stir up contaminated soil, such as working near chicken coops or in areas with bat droppings. Regular eye examinations are the best way to catch any early signs of POHS before they affect your vision.
Contact our experienced retina specialists to schedule a comprehensive eye exam. With regular check-ups and the latest treatments, we can help preserve your vision and address any concerns related to Presumed Ocular Histoplasmosis Syndrome. Don't wait—your vision is invaluable!
Discover insights on Presumed Ocular Histoplasmosis Syndrome (POHS), its symptoms, diagnosis, and effective treatment options.
