What is Ophthalmomyiasis?
Maggot infestations in people are not as rare as one might think. This can even happen on the surface of the eye and has been reported around the world. The term “myiasis” comes from a Greek word that means “fly.” It’s used to describe a condition where fly larvae, commonly known as maggots, infest a person.
When these maggots infest the eye, it’s called “ophthalmomyiasis.” If the infestation only affects the eye’s surface or the area around the eye, it’s called “ophthalmomyiasis externa.” However, if a larva penetrates into the eye, then it’s referred to as “ophthalmomyiasis interna.”
Often, this disease isn’t reported as much as it should be, and it contributes to discomfort and illness. Since it’s not very common, it’s important to know the symptoms in order to suspect it when necessary. In the past, people thought this disease was linked to poor hygiene, but recent studies have shown that it can occur regardless of hygiene levels.
What Causes Ophthalmomyiasis?
Ophthalmomyiasis, a condition affecting the eyes, can vary depending on the type of larvae causing it. Some larvae, referred to as “facultative parasites,” thrive in dead, decaying tissues, while others, termed “obligate parasites,” need healthy living tissues and often penetrate the inside of the eye.
Several different types of fly larvae can cause ophthalmomyiasis, including:
1. Oestrus ovis, also known as the sheep botfly
2. Phaenicia lucilia
3. Dermatobia hominis
4. Musca domestica
5. Hypoderma tarandi, or the cattle botfly
6. Several others including Fannia (also known as the latrine fly) and Alliphora, Lucilla, Sarcophaga, Gasterophilus, Callitroga, Cuterebra Dermatobia, Wohlfahrtia, Oedemagena, Chrysomya bezziana and Cochliomyia.
The most common cause of a form of this condition that affects the outer part of the eye (ophthalmomyiasis externa) is the larvae of the Oestrus ovis, or sheep botfly. But the condition affecting the inside of the eye (ophthalmomyiasis interna) is often caused by the larvae of Dermatobia hominis, Chrysoma bezziana, Hypoderma tarandi, or Cephenemyia trompe.
Risk Factors and Frequency for Ophthalmomyiasis
Ophthalmomyiasis is often seen in people who work closely with animals, such as farmers and those involved in animal husbandry. It’s commonly found in tropical areas, particularly in rural areas where hygiene might be lacking, and there are a lot of flies. Nevertheless, the disease can also affect those who aren’t involved in these professions.
People might accidentally encounter female flies that carry larvae, which can then enter their eyes. This disease, caused by specific types of flies, has been reported not just in tropical and subtropical regions, but also in colder areas like northern Canada.
Meanwhile, other factors that can make someone more likely to get ophthalmomyiasis include open surgical wounds, old age, being in a weak state, and poor overall health.
- Ophthalmomyiasis is often seen in people working closely with animals.
- It’s common in tropical regions, especially in rural areas with poor hygiene and a lot of flies.
- The disease can also affect people outside of these work situations.
- Unintentional contact with female flies carrying larvae can lead to the disease.
- Ophthalmomyiasis has been reported from India, Afghanistan, Iran, America, France, South Africa, the Middle East, Russia, Siberia, and even northern Canada.
- Other risk factors for ophthalmomyiasis include open surgical wounds, old age, poor health, and weakened physical conditions.
Signs and Symptoms of Ophthalmomyiasis
Ophthalmomyiasis is a disease often found in people working closely with specific animals such as goats, sheep, reindeer, or caribou, depending on the location. In some instances, a fly might strike the eye, leading to a type of ophthalmomyiasis caused by Oestrus ovis. This condition can give symptoms similar to bacterial or viral conjunctivitis. Signs can include eye pain, itching, redness, eyelid swelling, a sensation of something moving over the eye, and tiny blood spots under the conjunctiva, the clear tissue covering the white part of the eye. The patient may also experience a watery or mucous-like discharge from the eye.
A different type of ophthalmomyiasis, caused by Dermatobia hominis, can result in swelling of the eyelid that resembles a chalazion, a small, typically non-painful lump along the eyelid. In these cases, small larvae may be seen coming from the center of the lump on the conjunctiva.
Ophthalmomyiasis can also affect the inside of the eye, either the front (anterior) or the back (posterior) parts. The less common anterior ophthalmomyiasis results in uveitis, an inflammation of the middle layer of the eye. In such cases, moving larvae might be seen in the anterior chamber of the eye, the front part of the eye between the cornea and the iris, but there’s also a risk that the larvae could move toward the back of the eye.
- Photopsia (flashy visual disturbances)
- Eye pain
- Floaters (small shapes drifting in the field of vision)
Grey-white tracks might be seen on the retina, sometimes accompanied by detachment of the retina and vitritis, an inflammation of the vitreous, the clear jelly-like substance inside the eye. In severe cases, ophthalmomyiasis can lead to proliferation of fibrovascular tissue, localized bleeding, displacement of the lens, and disc edema, a swelling of the optic disc, the part where the optic nerve enters the eye.
Orbital myiasis, an infestation of the orbit, the bony cavity that contains the eyeball, applying pressure on the brain, is considered extremely dangerous, especially in patients with uncontrolled diabetes, old age, and generally poor health. This type of ophthalmomyiasis progresses rapidly and can extensively destroy the orbit’s tissues within a few days. It often starts in open surgical wounds, traumatic wounds or ulcers, and is associated with a rural environment, alcoholism, a stuporous condition, being bed-bound, poor self-care, poor hygiene, and malignant tumors around the eye socket.
Testing for Ophthalmomyiasis
If you have a condition called ophthalmomyiasis externa, it is possible that it might be mistaken for a simple eye infection such as viral or bacterial conjunctivitis. Therefore, a detailed eye exam is necessary. This condition is caused by the larvae of a fly called Oestrus ovis which like to hide in the folds or corners of your eyes because they are light-sensitive.
Undergoing a thorough eye examination using a device called a slit lamp often helps in correctly diagnosing the condition. Sometimes, multiple small areas of bleeding may occur in the eye, which is due to minor injuries caused by the spines and hooks on the larvae. If there is eyelid swelling or a sensation of movement underneath your eyelid, it is important to closely examine the swollen region with a slit-lamp, using high magnification. In some cases, eyelid swelling can occur due to another fly called Dermatobia hominis which can be seen through a hole in the center of the swelling area.
In cases of the condition progressing internally, known as ophthalmomyiasis interna, another kind of eye exam called a dilated fundus examination is performed to help identify the problem. This exam might show multiple trails underneath the retina layer of your eye. These can also be spotted using a technique called optical coherence tomography, which creates cross-sectional pictures of your retina. In some cases, there can be fluid buildup in the eye or inflammation. A test called Fundus Fluorescein Angiogram, which uses dye to illuminate the blood vessels in the eye, will reveal these trails more clearly and can show leakage from the optic disc or the spot where the optic nerve enters the eyeball, this is dependent on whether there is swelling in the disc or not. Another test known as Fundus autofluorescence may also highlight these trails.
To get a specific diagnosis, insect specialists or entomologists are often brought in. The larva of Oestrus ovis have hooks that are placed towards the front and connected to a structure termed as cephalo-pharyngeal skeleton. If you’re experiencing orbital myiasis, which is when the infection spreads to the eye socket, scanning the eye socket, brain, and paranasal sinuses or the air cavities around your nose would be necessary. The larvae should be sent for examination by an insect specialist, stored in a container with 70% ethanol.
Treatment Options for Ophthalmomyiasis
If you have external ophthalmomyiasis, meaning a type of eye infection caused by larvae, usually the condition will clear up on its own. However, it may be necessary to remove the larvae from the surface of your eye to speed up the healing process. This is typically done by numbing the surface of the eye with a local anesthetic and using delicate instruments to remove the larvae.
Once the larvae have been removed, your eye will be thoroughly examined to ensure that no more larvae are present. It’s important to examine all areas of the eye, including the parts under the eyelids. After this, your doctor will likely prescribe antibiotic eye drops or ointment to fight any infection, as well as steroid eye drops to reduce inflammation.
In an in-vitro study, which is a study performed outside of a living organism, it was found that a solution containing 1% Ivermectin, a type of medicine known for treating a variety of parasite infections, was effective at killing the larvae.
In cases of internal ophthalmomyiasis, meaning the larvae have burrowed into deeper parts of the eye, a different approach may be needed. This can include using a special kind of laser to kill the larvae, or using Ivermectin to treat them. In more severe cases, the larvae may need to be physically removed from within the eye, a process known as vitrectomy. Sometimes, larvae that are dead and not causing inflammation can just be left alone and observed.
If a larva has entered the anterior chamber, or front part of the eye, urgent removal through a minor surgical procedure may be needed. This is because the larva can quickly move deeper into the eye, causing more damage.
There is also a small chance that the larvae can exit through the optic nerve, leading to vision loss. In these cases, Ivermectin, a medication used to treat worm infestations, and steroids may be used to help restore vision.
The most severe complication of this infection is the possibility of the larvae spreading to the brain. This rare complication can be prevented with a surgery known as orbital exenteration. If the patient’s overall health is poor or if they have uncontrolled diabetes, efforts are made to control their blood sugar and ensure they are getting proper nutrition.
In cases where the infection has spread to the area around the eye, treatment might involve applying a topical anesthetic and turpentine oil to immobilize the larvae. After this, the larvae are manually removed and antibiotics are prescribed. Regular cleaning and dressing of the affected area are essential elements of recovery.
What else can Ophthalmomyiasis be?
Ophthalmomyiasis externa, a condition caused by larvae in the eye, often appears similar to adenoviral conjunctivitis, which is a type of pink eye. This is due to the small spots of bleeding caused by the larvae, which look much the same as those seen in cases of adenoviral conjunctivitis.
Similarly, both anterior ophthalmomyiasis interna (another variation of this condition where the larvae are in the front part of the eye) and anterior uveitis (swelling and irritation of the middle layer of the eye) exhibit a severe reaction in the anterior chamber, the front section of the eye. However, in cases of anterior ophthalmomyiasis interna, the larva can also be observed in the anterior chamber.
Posterior ophthalmomyiasis, where larva is in the back part of the eye, can be mistaken for an exudative retinal detachment (accumulation of fluid under the retina), especially in zones where this is common and if there’s history of exposure. Extra care should therefore be taken in the examination of these cases.
- Diffuse unilateral subacute neuroretinitis (DUSN) is another condition that may confuse the diagnosis of posterior ophthalmomyiasis. DUSN typically exhibits thinner subretinal tracks and relates to damage caused by nematode larvae.
- In the case of DUSN, both inner and outer layers of the retina are disrupted, even though the larva is located beneath the retina.
- Typical early signs are inflammation within the jelly-like substance filling the eye, swelling of the optic disc, and groups of white lesions on the retina. If a moving nematode is detected, it must be swiftly neutralized with a laser treatment since it could move quickly and become undetectable afterwards.
- In later stages, symptoms of unilateral retinitis pigmentosa may develop such as discoloration of the optic disc, thinning of the retinal arteries, and changes in the pigmentation of the retinal periphery.
Lastly, the chigoe flea, or Tunga penetrans, which burrows into the skin, can look similar to Dermatobia hominis larvae.
What to expect with Ophthalmomyiasis
External ophthalmomyiasis is a condition that does not generally cause severe damage to the eye and tends to resolve on its own. However, if it’s not treated promptly, it can potentially progress to internal ophthalmomyiasis – a more serious condition. Internal ophthalmomyiasis occurs when the larvae burrow into the retina, the part of the eye that senses light, causing significant damage.
If detected early, a treatment called photocoagulation can be used to treat the condition with a relatively good outlook. Despite substantial involvement in the retina, individuals may experience less vision impairment and a good recovery is possible.
However, delayed diagnosis can result in permanent vision loss and even death in severe cases that affect the orbit (eye socket) due to bone and surrounding tissue destruction. Even when the optic nerve (which sends visual signals to the brain) is affected, the outlook can be positive if treated adequately and promptly with medications such as ivermectin and steroids like prednisolone.
Possible Complications When Diagnosed with Ophthalmomyiasis
The complications of ophthalmomyiasis — an eye disorder caused by fly larvae — can range from minor eye problems to permanent loss of sight. This condition may also lead to physical disfigurement and can potentially be life-threatening.
- Ophthalmomyiasis externa, one variant of the disorder, has the potential to progress into ophthalmomyiasis interna, which is a more severe form of the condition.
- Ophthalmomyiasis interna can trigger a host of serious complications like the detachment of the light-sensitive tissue at the back of your eye (exudative retinal detachment), inflammation within your eye (vitritis), displacement of your eye lens (lens subluxation), complete dislocation of the lens, and invasion of your optic nerve.
- Orbital myiasis, another form of this disorder that affects the bony cavity that houses your eye, can even spread to the brain, which can ultimately lead to death.
Preventing Ophthalmomyiasis
People who work closely with animals should monitor any symptoms related to their eyes. If they notice any changes or issues, it’s critical to see an eye doctor as soon as possible. Symptoms or problems with the eyes that occur after being around a fly should be taken seriously.
Prevention is always the best approach to managing health. Good personal hygiene can help prevent serious eye conditions caused by a disease called ophthalmomyiasis, which is caused by fly larvae. In the past, there have been attempts to control outbreaks of this illness by having sterilized flies mate with fertile male flies.
A medication called Ivermectin, in the form of controlled-release capsules, can also be used to prevent animals from getting infested with a type of fly commonly known as the bot fly. This, in turn, helps to prevent humans from getting ophthalmomyiasis. Since people working with animals are at a higher risk of this disease, it’s important to take these specific preventative actions.