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Ocular toxocariasis is uncommon, but it can lead to blindness and other debilitating eye problems. It results from a parasitic roundworm infection.
There are surgical and medical treatments, depending on the severity of the condition. Doctors may prescribe corticosteroids, anthelmintic drugs, or surgery for complications, such as retinal detachment.
Toxocariasis is a type of infection that animals can transmit to humans. In the U.S., it is believed that tens of millions of people have been exposed to this infection. However, many people exposed to the Toxocara parasite never get sick. (Learn More)
The two primary syndromes associated with this infection include ocular toxocariasis and systemic toxocariasis. The ocular type occurs when the Toxocara larvae migrate into the eye, affecting the optic nerve or eye.
Due to the potentially devastating effects that this condition can have on an affected eye, it is imperative that all suspected cases receive a prompt diagnosis. This is usually done via an ELISA test to ensure a definitive diagnosis. (Learn More)
There are treatment options doctors can prescribe, with corticosteroids often being one of the first considered when there is active intraocular inflammation present. (Learn More)
Since the initial toxocariasis infection is not uncommon, everyone should take proper preventative measures. By preventing the initial infection, people can stop the development of ocular toxocariasis. (Learn More)
What Is Toxocariasis?
In the U.S., it is estimated that approximately 14 percent of the population have experienced this infection. People who own dogs have a higher risk of getting it. However, it is also possible for cat feces to transmit the infection.
This infection is seen more often among people in hot and humid regions, and those who live in poverty.
A toxocariasis infection can develop when someone accidentally ingests Toxocara eggs. The eggs hatch after they get into the body.
Via the bloodstream, the roundworm larvae get into different areas of the body. The eyes are one structure they can travel to as well as the liver, lungs, muscles, heart, and brain.
In most cases, people do not experience any symptoms. However, if the larvae cause damage to organs or tissues, symptoms may include fever, liver inflammation, coughing, and eye problems.
What Is Ocular Toxocariasis?
If a toxocariasis infection affects the eyes, ocular toxocariasis can develop.
In approximately 90 percent of people, only one eye is affected. Traditionally, experts believed that young children and infants were primarily the ones who contracted this infection, but recent surveys have discovered that it has also been observed in young adults and teenagers.
The primary symptoms include floaters and blurry vision. Sensitivity to light and pain are also possible, but these are usually mild.
For young children, this eye infection might not be noticed until they develop leukocoria or strabismus, or they fail a vision screening at school, according to Review of Ophthalmology.
Leukocoria describes an abnormal white reflection that comes from the eye’s retina.
Strabismus is a misalignment of the eyes. This can be outward or inward.
When ocular toxocariasis is suspected, the doctor usually starts with an ophthalmologic examination. The doctor is looking for the signs of this condition, such as a retinal granuloma. This granuloma is a mass that is inflammatory and whitish to yellowish in color. It is typically found in the peripheral retina or posterior pole.
The doctor may also be looking for comorbid conditions that may be present with the granuloma, such as:
- Epiretinal membrane. This condition is characterized by scar tissue forming a thin layer on the retina’s surface.
- Retinal detachment. The retina comes apart from its attachment points.
- Macular edema. This condition occurs when fluid accumulates in the macula component of the retina.
These comorbid issues could cause permanent vision loss in the eye where ocular toxocariasis is present.
To confirm the diagnosis, the doctor usually does serological testing, which typically consists of enzyme-linked immunosorbent assay (ELISA). With this test, they are looking for the serum antibody associated with Toxocara larvae.
- Corticosteroids: When someone has intraocular inflammation, corticosteroids are typically prescribed. These are usually given orally to alleviate inflammation. It is important to take the medicine exactly as prescribed.The doctor may also make diet recommendations, such as watching sugar intake. This is because corticosteroids can increase blood sugar levels.
- Anthelmintic drugs: With ocular toxocariasis, using anthelmintic drugs to treat the infection remains controversial. However, it may still be considered for some people. These drugs are typically used for the systemic form of this infection. When doctors prescribe this type of medication, it is usually given along with a corticosteroid drug.
- Photocoagulation: One report explored using photocoagulation for this infection. The report states that this treatment destroyed motile subretinal larva.Photocoagulation is considered a surgical procedure. It works to destroy or shrink retinal structures that are abnormal. It can also cause scarring intentionally to treat an issue with the retina.
The doctor uses a laser for this procedure. It causes a microscopic burn. This treatment tends to be the most effective when it is used early in the condition. If the person has already lost vision as a result of this infection, this treatment cannot bring it back. However, it can help to reduce the risk of further or permanent vision loss.
- Ranibizumab: In some cases, people develop choroidal neovascularization as a result of ocular toxocariasis. Choroidal neovascularization is characterized by the development of new blood vessels in the eye’s choroid layer. One report showed that the medication ranibizumab was effective for treating this issue when it was administered intravitreally.
Ranibizumab is a medication that is most commonly used to treat the wet form of age-related macular degeneration. Since it may help to reduce macular edema that occurs as a result of a retinal vein occlusion, it may be beneficial for this issue.
This drug is classified as a vascular endothelial growth factor A agonist. Its mechanism of action is to stop the growth of abnormal blood vessels. It also works to stop eye leakage that might lead to vision loss.
This drug comes in a liquid form. When a doctor prescribes it as a treatment for ocular toxocariasis, it is injected directly into the affected eye.
On average, this medicine is administered approximately once a month, and only into the affected eye. The injections can be done in a doctor’s office.
- Surgery: If someone experiences epiretinal membrane, retinal detachment, or persistent vitreous opacity, surgery is often indicated. The exact procedure performed depends on the condition the person is experiencing and its overall severity.
Preventing an Infection
There are methods people can use to reduce their risk of this infection. Anyone who has cats or dogs should have their pets checked for worms regularly, especially if they spend time outside.
At least once a week, clean the pet’s living area and food and water bowls. After dealing with pet feces, immediately wash your hands with soap and water. Wearing disposal gloves when handling pet feces is also a good idea.
Since the eggs can be found in soil, after gardening or otherwise touching dirt or soil, wash your hands. Teach children to never eat soil or dirt since this puts them at risk for ingesting the eggs.
Also, make sure that any sandboxes are covered when not in use to prevent animals from using them as a litterbox.
Toxocara eggs are resilient and can live for years when the right conditions are present due to their strong protective layer. These eggs are not killed by most common disinfectants. Because of this, using caution when handling animal feces and removing any feces right away are important measures.
Once the eggs come out of an animal, they are not infective for two to four weeks, so proper cleaning to remove anything that could include the eggs is imperative.
Anyone who develops a toxocariasis infection should be aware of the potential for ocular toxocariasis. Seeking prompt treatment is important regardless of whether the condition starts to affect the eyes.
Ocular Toxocariasis – United States, 2009-2010. Centers for Disease Control and Prevention.
Epidemiology and Risk Factors. Centers for Disease Control and Prevention.
Detection and Treatment of Ocular Toxocariasis. Review of Ophthalmology.
Ocular Toxocariasis: A Review. Survey of Ophthalmology.
Prevention and Control. Centers for Disease Control and Prevention.
What Is the Connection Between Prednisone and Diabetes? Medical News Today.
A Case of Ocular Toxocariasis Treated by Xenon Photocoagulation. Klinika Oczna.
Ocular Toxocariasis: Clinical Features, Diagnosis, Treatment, and Prevention. Asia Pacific Allergy.