Eye Worms
What Are Eye Worms?
Several different types of parasitic worms can infect the human eye. The most common include Loa loa, which is also called the African eye worm, and Thelazia species, which are found in various parts of Asia and North America. Other less common parasites include Dirofilaria and Onchocerca species.
Each type of worm has a different life cycle and method of transmission. Understanding which parasite is causing your infection helps us determine the best treatment approach. Thelazia callipaeda is now established across parts of Europe, while human Thelazia infections in North America are rare and mainly reported in the western United States. Onchocerca volvulus causes onchocerciasis with microfilariae that can affect the cornea and anterior segment.
These parasites typically enter the human body through insect bites or direct contact with infected flies. Most vectors are day-biting. Once inside the body, the worms can migrate through tissues and eventually reach the eye. Some parasites are deposited directly onto the eye surface by flies that feed on eye secretions.
The journey from initial infection to eye symptoms can take weeks or even months depending on the parasite type. During this time, the worm grows and develops as it moves through your body.
Eye worm infections are most common in specific regions of the world. Loa loa is primarily found in Central and West Africa, especially in rainforest areas. Thelazia infections occur in parts of Asia, including China, Japan, Korea, and Thailand, as well as in some western states of North America.
- Central and West African rainforests for Loa loa infections
- East and Southeast Asian countries and parts of Europe for Thelazia species
- Rural areas of California, Oregon, and other western states for rare sporadic cases
- Parts of Europe, including Russia, for Thelazia callipaeda
- India and other South Asian countries for Thelazia and other parasites
- Onchocerciasis endemic regions in sub-Saharan Africa, focal areas of Latin America, and Yemen
Signs You May Have Eye Worms
The most obvious sign of an eye worm infection is actually seeing the worm moving across the white part of your eye or under the eyelid. Many patients first notice this when looking in a mirror or when someone else points it out. The worm may appear as a thin white or translucent thread moving slowly across the eye surface.
This visible movement can be alarming, but it actually makes diagnosis much easier. If you see something moving in your eye, contact our office immediately for examination.
Eye worms cause inflammation and irritation as they move around the eye. You may experience persistent redness that does not improve with over-the-counter eye drops. The eye often produces extra tears in an attempt to wash away the irritation.
Some patients also report a scratchy or gritty feeling, similar to having sand in the eye. This irritation may come and go as the worm moves to different locations.
As the infection progresses, you may become more sensitive to light than usual. Bright lights might cause discomfort or pain, making it difficult to go outside on sunny days or work under fluorescent lighting. Blurred vision can develop if the worm crosses over the pupil or if inflammation affects the cornea.
- Increased discomfort in bright sunlight or artificial light
- Difficulty focusing on objects clearly
- Temporary vision changes as the worm moves
- Watery eyes when exposed to light
Many patients describe a crawling or wiggling sensation inside the eye or under the eyelid. This feeling occurs because the worm is actually moving through the tissues. The sensation may be intermittent and can be quite disturbing even if you cannot see the worm directly.
This symptom often comes and goes throughout the day. You might feel it more when you blink or move your eyes in certain directions.
Seek medical attention right away if you see a worm in your eye or experience sudden vision loss. Severe eye pain, significant swelling, or discharge that looks like pus also require prompt evaluation. Any symptoms that develop after traveling to areas where eye worms are common should be evaluated quickly. Do not attempt to remove a worm yourself, and avoid using over-the-counter steroid drops until you are examined.
Early treatment prevents complications and protects your vision. We recommend scheduling an appointment as soon as you notice any unusual eye symptoms, especially if you have recently traveled internationally. If you have recently returned from Central or West Africa, seek care urgently before taking any antiparasitic medications.
Who Is at Risk for Eye Worms
People who travel to or live in areas where eye worms are common face the highest risk of infection. Even short trips to endemic regions can result in exposure if you are bitten by the right type of insect. Travelers who spend time outdoors in rural or forested areas have greater exposure than those who stay in urban environments.
- Tourism or work in Central or West African countries
- Extended stays in rural Asian communities
- Camping or hiking in endemic regions
- Mission trips or volunteer work in high-risk areas
Specific types of flies transmit eye worms to humans. Chrysops deer flies transmit Loa loa, while lachryphagous flies that feed on eye secretions spread Thelazia species. These insects typically bite during daytime hours and are attracted to areas near water or vegetation.
The flies deposit parasite larvae when they bite or land on your skin or eyes. Not all bites result in infection, but repeated exposure increases your risk.
Spending time outdoors in endemic regions significantly raises your chance of encountering infected insects. Activities like hiking, camping, fishing, hunting, or working in agriculture expose you to more insect bites. People who work outside during daylight hours when the carrier flies are most active face ongoing risk.
Even brief outdoor exposure can lead to infection if conditions are right. Protective measures become especially important during peak fly season in affected areas.
Certain jobs increase your likelihood of eye worm infection. Forest workers, agricultural laborers, field researchers, and wildlife professionals spend long hours outdoors in endemic areas. Military personnel deployed to affected regions may also face elevated risk.
- Forestry and logging operations
- Agricultural work in endemic countries
- Biological field research and surveys
- Conservation and wildlife management
- Military service in tropical regions
How We Diagnose Eye Worms
We begin by carefully examining your eye using specialized equipment. A slit lamp microscope allows us to see fine details of the eye surface and look for signs of parasitic infection. We check under your eyelids and examine the conjunctiva, which is the clear tissue covering the white part of the eye.
During the exam, we ask you to look in different directions so we can view all areas where a worm might hide. This thorough examination usually reveals the parasite if it is present on the eye surface. We may evert the eyelids and examine the conjunctival fornices where worms often hide.
In most cases, we can directly see the worm moving on or under the surface of your eye. We may use a special light and magnification to get a clear view of the parasite. Sometimes we need to gently lift your eyelid to find a worm that has migrated underneath.
Seeing the actual worm provides immediate confirmation of the diagnosis. We may take photographs or videos to document the infection and help identify the specific type of parasite.
After removing the worm, we send it to a laboratory for identification. Experts examine the parasite under a microscope to determine the exact species. This information helps us decide whether additional treatment with medications is necessary.
- Microscopic examination and species identification of the removed worm
- Midday thick blood smear or quantitative PCR for Loa loa microfilariae when exposure is possible
- Skin snips for suspected onchocerciasis
- Eosinophil count and other targeted tests based on travel and exposure history
If we suspect the parasite has invaded deeper eye structures, we may recommend imaging studies. B-scan ultrasound of the eye can detect worms in areas we cannot see directly. Optical coherence tomography provides detailed cross-sectional images of the retina and other internal eye structures.
These advanced tests help us assess whether the infection has caused any damage to important parts of the eye. They also guide treatment decisions if the worm is located in a difficult-to-reach area.
Treatment Options for Eye Worms
The primary treatment for eye worms is physical removal of the parasite. We apply numbing drops to your eye to ensure you are comfortable during the procedure. Using fine forceps or other specialized instruments, we carefully extract the worm from the eye surface or from under the eyelid.
This procedure is typically quick and performed in our office. Many patients feel rapid relief once the worm is removed, though some inflammation may persist temporarily. Removal is performed by an ophthalmologist under magnification to minimize trauma.
Medication choice and timing depend on the species and microfilarial load, and we coordinate with Infectious Disease or Tropical Medicine for systemic therapy when indicated. Depending on the type of parasite and whether we find evidence of infection elsewhere in your body, we may recommend antiparasitic medications. These drugs help eliminate any remaining larvae or adult worms that might be present in other tissues. Treatment duration varies based on the specific parasite species.
- Loa loa: diethylcarbamazine is the usual first-line agent. In patients with high microfilarial loads, pretreatment strategies such as albendazole debulking and close monitoring are used to reduce the risk of serious adverse reactions.
- Onchocerca: repeated ivermectin dosing to clear microfilariae, often combined with doxycycline targeting Wolbachia. Screen for Loa loa coinfection before ivermectin.
- Thelazia: mechanical removal is primary; topical therapy may be used for associated inflammation.
- Dirofilaria: surgical excision of subconjunctival or periocular nodules.
After removing the worm, we may prescribe topical anti-inflammatory drops, and antibiotic drops if there is an epithelial defect or if your surgeon recommends prophylaxis. These medications help your eye heal more quickly and prevent complications.
We provide specific instructions on how often to use the drops and for how long. We will tailor drop selection and duration to the degree of surface injury and inflammation.
We schedule follow-up appointments to monitor your recovery and ensure the infection has completely resolved. During these visits, we examine your eye to confirm there are no additional parasites and that inflammation is improving. We also check for any complications or lasting effects on your vision.
If you received systemic antiparasitic medication, we may order additional tests to confirm the treatment was effective and monitor for allergic or neurologic reactions during the first several days after treatment. Follow-up with Infectious Disease may be recommended for systemic evaluation. Resolution often occurs within a few weeks, though some cases require longer monitoring.
Preventing Eye Worm Infections
If you plan to visit areas where eye worms are common, take steps to protect yourself from insect bites. Wear long sleeves and long pants, especially during daytime hours when carrier flies are most active, since these vectors primarily bite during daylight. Choose accommodations with screened windows and doors when possible.
- Stay in screened or air-conditioned buildings when feasible
- Wear protective clothing that covers arms and legs
- Use protective measures during daylight hours when vector flies are most active
- Sleep under bed nets treated with insecticide (nets are less protective against day-biting flies but help against other insects)
- Plan activities with full daytime protection, as many vector flies are active throughout daylight
Use EPA-registered repellents with DEET 20 to 50 percent or picaridin 20 percent on exposed skin, and reapply as directed, especially if you are sweating or swimming. Treat clothing and gear with permethrin for additional protection. Apply repellent around, not directly into, the eyes. Consider head nets and wraparound eyewear in high-risk areas.
Wearing sunglasses or protective eyewear creates a physical barrier between flies and your eyes. Wide-brimmed hats also help keep insects away from your face.
Limit time spent in heavily forested areas or near water sources where flies congregate. If you must be outdoors in these environments, increase your protective measures. Avoid touching your eyes with unwashed hands, as this could introduce parasites if you have contacted contaminated surfaces.
Stay informed about local disease risks before traveling to unfamiliar areas. Consult with a travel medicine specialist if you will be spending extended time in regions where eye worms and other parasites are common.
Frequently Asked Questions
Eye worms rarely resolve without treatment and waiting can lead to complications. The parasite may persist and cause ongoing inflammation or damage. Removal is necessary to resolve the infection and prevent complications.
No, you cannot catch eye worms directly from another person. The parasites require specific insect carriers to complete their life cycle and spread to new hosts. Your family members are not at risk from being near you, though they could become infected if exposed to the same insects in endemic areas.
Many people recover fully with prompt treatment and do not experience lasting vision problems. Permanent damage is rare but can occur if the infection is left untreated for a long time or if the worm invades deeper eye structures. Risk depends on the parasite species, location in the eye, and time to treatment. Early diagnosis and removal offer the best chance for complete recovery without vision loss.
The time between initial infection and noticeable eye symptoms varies widely depending on the parasite species. Some people may notice symptoms within weeks, while others do not develop symptoms for several months or longer. This delay occurs because the worm needs time to grow and migrate to the eye after entering your body.
The eye worms that infect humans are different from those that affect dogs, cats, and other animals. While pets can get their own parasitic eye infections, they do not directly transmit human eye worms. However, pets and humans in the same area may both be exposed to the insects that carry parasites. In some European regions, dogs serve as reservoirs for Thelazia callipaeda, so controlling pet infections reduces human exposure via vector flies.
Getting Help for Eye Worms
If you notice any signs of eye worms or develop unusual eye symptoms after traveling to endemic regions, we encourage you to contact our office right away. Early diagnosis and treatment provide the best outcomes and prevent potential complications. Our ophthalmologist has experience identifying and treating parasitic eye infections to protect your vision and restore your comfort.