What You Should Know About Ocular Histoplasmosis

What is the Ocular Histoplasmosis Syndrome?

The fungus is inhaled early in life and causes a usually asymptomatic and self-limited infection throughout the body, including the lungs and choroid (the vascular layer lining the retina). For unknown reasons, several decades after the initial infection, the choroidal scars may develop abnormal blood vessels (choroidal neovascularization) which leak fluid and blood. This leakage can only be seen on a careful, dilated eye examination since the eye looks normal from the outside. Distorted central vision and loss of reading vision occurs when the leakage involves the macula.

normalretina histo
Normal Macula. Histoplasmosis with scarring around
the nerve and in the macular center.

The goals of treatment are to prevent choroidal neovasculatization (CNVM) from spreading into the macular center (laser photocoagulation), or limit the size of and leakage from the CNVM once it reaches the macular center (photodynamic therapy, vascular endothelial growth factor inhibitors).

Who gets the Ocular Histoplasmosis Syndrome?

People who live in endemic areas, such as the Ohio-Mississippi river basin, who are exposed to the histoplasmosis fungus early in life are at greatest risk for developing eye problems later in life. A person with ocular histoplasmosis cannot infect other people since the organisms die soon after the initial infection. Adults who move to endemic areas, although they may get infected with the histoplasmosis fungus, do not usually develop eye disease.

normalvision armdvision
Normal Vision. Ocular Histoplasmosis.

What are the symptoms of the Ocular Histoplasmosis Syndrome?

People usually have no eye symptoms during the initial infection. The choroidal scars that later form also do not usually cause any symptoms. If leakage and bleeding involve the reading area of vision (the macula), symptoms such as distortion and loss of reading vision occur. Patients never go completely blind, since the part of the eye responsible for peripheral vision is not affected by this disease.

Patients are often asked to check their central vision every day with an Amsler grid. This grid is a pattern that resembles a checkerboard. You will be asked to cover one eye and stare at a black dot in the center of the grid. While staring at the dot, you may notice that the straight lines in the pattern appear wavy to you. You may notice that some of the lines are missing. These may be signs of choroidal neovascularization.

Click here to view or download a full-sized Amsler grid for yourself.

badamsler1 badamsler
Blurry areas and black spots. Wavy or crooked lines.

How do we diagnose the Ocular Histoplasmosis Syndrome?

The most important step in accurately diagnosing the ocular histoplasmosis syndrome consists of a careful eye examination by an eye doctor familiar with all aspects of this disease. During the examination, your doctor will dilate your pupils and look for histoplasmosis scarring, leakage, and bleeding. Your doctor may need to perform an OCT scan or fluorescein angiography to better evaluate the histoplasmosis scars.

What treatments are available for ocular histoplasmosis?

  1. Observation.

    Patients with inactive histoplasmosis scarring and those who have been successfully treated are asked to look at the Amsler Grid, daily for any central visual changes. If a change in the central vision or Amsler grid develops, the patient should seek prompt attention. A careful examination, OCT scan and fluorescein angiogram may be needed to look for choroidal neovascularization that can possibly be treated.

  2. Corticosteroids.

    Steroids are potent medicines that can reduce inflammation. Some doctors will occasionally recommend steroid pills or shots for the rare patient experiencing visual symptoms from acute histoplasmosis inflammation.

  3. Laser photocoagulation.

    retinallaserA laser is an instrument that produces a pure, high-intensity beam of light energy. The laser light can be focused onto the retina, selectively treating the desired area while leaving the surrounding tissues untouched. The absorbed energy heats, or photocoagulates, the retina creating a microscopic spot.

    Laser surgery is performed in our office while you are awake and comfortable. The laser is used to seal the leaking vessels beneath the retina. The laser treatment usually takes less than 15 minutes to complete, and you can go home immediately following surgery. Arrangements for transportation should be made in advance since you may not be able to drive right away.

    retinallaser postlaserohs
    Fluorescein angiogram showing
    choroidal neovascularization (arrow).
    Dry laser scar following successful
    laser photocoagulation surgery.

    Laser surgery, which became available in the early 1970's, still remains an excellent treatment option for neovascularization well away from the macular center. However for more central lesions, anti-VEGF agents and photodynamic therapy (available beginning in the early to mid-2000's) are recommended.

  4. Photodynamic therapy.

    Laser photocoagulation surgery has traditionally been the standard treatment for patients with ocular histoplasmosis and choroidal neovascularization outside the macular center. When choroidal neovascularization is beneath the center of the macula, laser not only destroys these abnormal vessels but also permanently damages the overlying retina. Patients are thus left with a dry scar but no central vision. Photodynamic therapy, which became available in 2000, was the first treatment that allowed treatment of these central lesions while minimizing retinal damage. The treatment involves injecting Verteporfin (Visudyne) intravenously, followed by a painless laser treatment. Direct daylight exposure within the first 48 hours can cause a severe skin burn, so patients need to remain inside for two days following treatment. Photodynamic therapy is painless and is associated with minimal to no side effects. It usually needs to be repeated every 3 months for multiple treatements for recurrent neovascularization.

    In an open label safety study involving 26 patients with ocular histoplasmosis, visual acuity improved by an average of more than 1 line on a standard eye chart at 12 months with 28% of patients experiencing a visual acuity improvement of 3 lines or more. Visual acuity decreased by less than 3 lines of vision in 88% of patients during the same time period.

    prepdtohs postpdtohs
    Macular hemorrhage before photodynamic therapy. All leakage resolved following photodynamic treatment. A dry central macular scar remains.

    Combining photodynamic treatment with injection of a VEGF-inhibitor or anti-inflammatory steroid medication (Kenalog) into the eye (a painless in-office procedure) appears to dramatically improve results. Patients appear to require far fewer photodynamic treatments with combination therapy.

  5. Vascular Endothelial Growth Factor (VEGF) Inhibitors.

    VEGF inhibitors (Avastin, Lucentis and Eylea) are a new class of potent medications that prevent choroidal neovascularization from growing and leaking. They have been extensively studied in patients with age-related macular degeneration, and are also highly effective in ocular histoplasmosis. Click here to learn more.

  6. Subretinal surgery.

    Using advanced surgical techniques, abnormal blood vessels growing beneath the part of the eye responsible for central vision can be removed. This surgery is sometimes successful in restoring reading vision, and appears mostly effective for eyes with vision worse than 20/100. Your doctor will discuss this option with you if he feels you could benefit from this procedure.

What happens if I lose my reading vision?

Except for airplane pilots, military personnel, surgeons, etc., most patients who lose reading vision in one eye usually continue their normal lifestyle and job without change. The major problem is adjusting to the initial lack of depth perception required for near vision. Eventually, patients learn to compensate for this and obtain new clues from the environment to judge close distances. Patients are usually able to thus gain back much of their lost depth perception. Patients should be able to drive a car as long as their vision in the good eye is at least 20/60.

Low Vision services and examination.

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We may recommend that you see a specialist for a low vision examination. Magnifying lenses or other devices can be prescribed to help with reading and other central vision tasks.

For those living in the Kentuckiana area, the Kentucky Office for the Blind, the Free Kentucky Talking Book Library Service,  and the American Printing House for the Bind offer a myriad of services and resources to help those with vision loss function better and remain independent. See the World, located at 1832 Frankfort Avenue in Louisville, is a locally-owned retail store that has a wide range of special products including magnifiers, canes, talking clocks and watches, money identifiers and more.

Radio Eye is a non-profit 24-hour radio service that broadcasts the reading of current newspapers and other everyday literature, offering greater independent living to people who are blind, visually impaired or physically handicapped. Radio Eye radio listeners hear the reading of dozens of newspapers, magazines, health materials, grocery ads and much more. The audio stream can be accessed on a special (free) Radio Eye radio, on Library Channel 20 on Lexington Insight Cable TV, in area homes and hospitals, and on the internet at www.RadioEye.org.

The low vision experts at Lighthouse International have created Living Better at Home: A Guide for People with Vision Loss. This is a national campaign to promote safety, independence, and accessibility in the home. Please click here to learn more about available online content and a free printed kit filled with useful information and products.

What are my chances of abnormal blood vessels affecting my good eye?

Patients who have no signs of abnormal blood vessels in either eye have a minimal chance of losing central vision. This risk is increased, however, if abnormal blood vessels have already affected one eye. The yearly risk for the second eye becoming involved then increases to approximately 1 in 50.

What can I do to prevent visual loss from histoplasmosis?

There is nothing that a person with histoplasmosis can do to prevent abnormal vessels from developing. The most important thing is to carefully monitor the central vision with daily vision checks (including the Amsler grid) and frequent, regular eye examinations. Any sudden change in the central vision necessitates an immediate examination by your eye doctor.




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