Eye Parasites: Symptoms, Diagnosis & Treatment

Marcela Lemos
Clinical review: Marcela Lemos Biomedical Scientist CRBM/PE #08598
Created by: Jillian Kinton-Vieira Registered Nurse

Eye parasites (also called loiasis) is an infection caused by the Loa loa larva. The larva can migrate toward the eye area and trigger symptoms like irritation, pain, itching, and redness.

This infection is most often linked to repeated bites from deer flies, which can deposit larvae into the bloodstream. Over time, the larvae can travel and develop, and adult worms can release new larvae back into the blood.

Treatment for eye parasites should be guided by an ophthalmologist. They may recommend eye drops to ease symptoms and oral medications to help eliminate the larvae from the body.

ophthalmologist examining patient's eye

Main symptoms

The main symptoms of eye parasites include:

  • Blurry vision;

  • Itchy or painful eye;

  • Redness in the eye;

  • Dark spots in the field of vision;

  • Increased sensitivity to light.

According to the CDC, Loa loa infection often causes no symptoms. In more advanced stages, symptoms may appear, and in some cases the larva can be seen in the eye.

In most cases, eye parasites affect only one eye, but both eyes can be involved.

The larva can also remain in the skin. When that happens, small painless lumps may appear on the arms and legs, especially near joints.

Confirming a diagnosis

The diagnosis of eye parasites is made by an ophthalmologist or a primary care provider based on symptoms and a physical exam of the affected eye.

The provider may also order tests to look for larvae in the blood or antibodies against Loa loa, which can help confirm the diagnosis.

Transmission and spread

The Loa loa larva is transmitted through the bite of deer flies in the Chrysops genus.

When the fly bites, it can pass larvae into the bloodstream. These larvae may reach the conjunctiva (the white part of the eye) and lead to symptoms.

This type of infection is more common in certain regions of Africa, according to the World Health Organization (WHO).

Treatment options

Treatment for an eye larva should be guided by an ophthalmologist. The plan can vary depending on how developed the larva is and how severe the symptoms are.

The main treatments for eye parasites include:

1. Use of medications

The main medications for eye parasites that may be prescribed by an ophthalmologist include:

  • Anti-inflammatory drugs, such as flurbiprofen or diclofenac: may be used as eye drops or oral tablets to help relieve pain, redness, and itching;

  • Antiparasitic medications, such as albendazole, ivermectin, or mebendazole: taken orally to help eliminate larvae from the body;

  • Corticosteroids, such as prednisolone or hydrocortisone: usually used as eye drops to help relieve itching and other symptoms.

These medications should always be used under the guidance of an ophthalmologist, based on the symptoms present.

2. Surgery

In more advanced cases, surgery may be recommended to remove larvae from the eye, especially those closer to the surface.

However, surgery does not cure the disease. Medications should still be continued as prescribed by a healthcare provider.

Are eye parasites curable?

Eye parasite infection caused by the Loa loa larva can be cured when treatment is done as directed by an ophthalmologist.

Treatment usually has good results, and most people do not have lasting complications.

In more severe cases, vision problems may still occur even after treatment.

Prevention tips

Some ways to help prevent Loa loa larvae from settling in the body after a fly bite include:

  • Avoiding muddy areas, especially shaded places or areas near rivers;

  • Applying insect repellent to exposed skin;

  • Wearing long-sleeved shirts to reduce skin exposure;

  • Choosing pants instead of shorts or skirts.

Deer flies are usually more active during the daytime. Because of that, these precautions are especially important when you are outdoors during daylight hours.

Update History
We regularly update our content with the latest scientific information to maintain an exceptional level of quality.

References
  • Centers for Disease Control and Prevention. DPDx: laboratory identification of parasites of public health concern. Loiasis. Centers for Disease Control and Prevention. Updated 06 Jun 2024. Accessed 05 Feb 2026 https://www.cdc.gov/dpdx/loiasis/index.html
  • Global Onchocerciasis Network for Elimination (GONE). GONE webinar: Loiasis - a very neglected disease in Central Africa. World Health Organization. Updated 04 Dec 2025. Accessed 05 Feb 2026 https://www.who.int/publications/m/item/gone-webinar--loiasis---a-very-neglected-disease-in-central-africa
  • RAMHARTER, M.; et al. The African eye worm: current understanding of the epidemiology, clinical disease, and treatment of loiasis. Lancet Infect Dis. 2024;24(3):e165-e178.
  • BENNURU, S.; et al. A Novel, Highly Sensitive Nucleic Acid Amplification Test Assay for the Diagnosis of Loiasis and its Use for Detection of Circulating Cell-Free DNA. J Infect Dis. 2023;228(7):936-943.
  • HASNAOUI, I.; et al. Ocular Loa loa filariasis. J Fr Ophtalmol. 2024;47(4):104124.
  • Barer, Michael R. Medical Microbiology: A guide to microbial infections - pathogenesis, immunity, laboratory investigation and control. 19 ed ed. : Elsevier; 2018.