Detection and Treatment of Ocular Toxoplasmosis

24 September, 2020
Ocular toxoplasmosis can lead to blurry vision, sensitivity to light, and pain in the eyes. However, diagnosing it can be complex and we'll explain why in today's article.

Ocular toxoplasmosis is a disease caused by a parasite called Toxoplasma gondii. It’s a very common infection that affects about 500 million people around the world. However, not all those infected develop this pathology that only affects the eyes.

People with symptoms or consequences of ocular toxoplasmosis either have a weakened immune system or acquired the infection before birth, in their mother’s womb. Unfortunately, their eye shape is often hard to detect and often progresses to blurry vision and even blindness.

What’s ocular toxoplasmosis?

In order to understand ocular toxoplasmosis, we must first explain how this parasitic infection occurs. Toxoplasma gondii multiplies and lodges in cats. Furthermore, they expel these bacteria whenever they do their business.

This is only one of the forms of contagion though. However, most people become infected because it’s also often present in food such as fruit, vegetables, meat, dairy, and even water. As you can see, anyone can acquire the infection when ingesting a contaminated uncooked product.

Also, pregnant women who come into contact with toxoplasma can pass it down to their baby. This is because the bacteria can cross the placenta and reach the fetus.

In fact, the latter case is the one most frequently associated with ocular toxoplasmosis. The seriousness of the fetal damage will depend on the stage of pregnancy in which the contact occurs. For instance, the first trimester is associated with the highest risk of malformations and complications.

A microscopic view of ocular toxoplasmosis.
Toxoplasma is a parasite that causes toxoplasmosis in all of its types, including the ocular one.

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Causes

The infection is usually asymptomatic at first. However, reactivation can occur after a certain time of contact, which would lead to an eye injury that produces a scar that usually goes unnoticed.

As the infection reactivates, the specific symptoms of ocular toxoplasmosis begin to appear. This happens when the parasite lodges in the retina — the part of the eye that allows the interpretation of images and the sense of vision. The retina becomes inflamed (this process is called retinitis) and compromises vision.

A study by a Society of Ophthalmology states that recurrent ocular toxoplasmosis is the most common type. However, it can also appear in relation to AIDS or under continuous treatment with corticosteroids or immunosuppressants.

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Detection of ocular toxoplasmosis

The diagnosis of ocular toxoplasmosis can be very complex and doctors should evaluate it on a clinical basis –that is, observe the eye lesions. This is because the available tests can only confirm whether there’s been contact with the parasite or not.

For example, serologies, which allow us to see if there are antibodies against said infection, only indicate if at some point that person’s had the infection. But, as we mentioned before, there are many who have and who didn’t develop ocular toxoplasmosis.

What an ophthalmologist directly observes is a focal lesion of the retina together with a scar that also affects the choroid — another membrane that’s part of the eye.

Laboratory tests can help guide the diagnosis, but don’t confirm it. Thus, it’s important that a specialist should carry out a thorough eye examination so as not to miss the nearly invisible signs.

A Toxoplasma test.
A blood serology for toxoplasmosis is indicative of contact with the parasite but doesn’t certify disease.

Treatment for ocular toxoplasmosis

Ocular toxoplasmosis causes blurred vision, eye pain, and photosensitivity. In some cases, it can even cause blindness. Unfortunately, there’s still no treatment with which to reverse any injuries.

Therapy helps prevent the extent of retinal damage as well as further recurrences. It keeps the parasite from replicating and spreading with the combination of antiparasitics such as pyrimethamine and sulfadiazine.

In addition, they often add methylprednisone, a corticosteroid that helps reduce inflammation. Similarly, they prescribe folic acid supplements to avoid the side effects of pyrimethamine.

Preventing damage

The most effective way to avoid ocular toxoplasmosis is to take preventive measures against it. Doctors recommend cooking all food properly to avoid contagion. In addition, there must be great emphasis on proper cat hygiene measures around pregnant women.

Finally, keep in mind that you must consult a doctor if you notice any symptoms. Finding injuries quickly can help prevent eye damage from spreading.

We hope you’ve enjoyed this article.

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