What are the other Names for this Condition? (Also known as/Synonyms)

• Internal Ophthalmomyiasis

What is Ophthalmomyiasis Interna? (Definition/Background Information)

• Myiasis is primarily a skin disease caused by several species of parasitic fly larva (of taxonomic order Diptera). The fly larvae (maggots) cause disease in humans and other vertebrate animals by feeding on the tissues. The infection is usually characterized by a painful, itchy, boil-like skin lesion that contains the parasite within it
• Ophthalmomyiasis Interna is a form of ophthalmomyiasis (also termed oculomyiasis), where the anterior or posterior segment eye structures are infected by myiasis. The anterior segment includes the cornea, iris, ciliary body, and lens; while, the posterior segment includes the vitreous humor, retina, choroid, and optic nerve. Rarely, Ophthalmomyiasis Interna may be a complication of ophthalmomyiasis externa
• In most cases, the causative parasites are the warble flies (also called heel flies) belonging to Hypoderma species that is mostly seen in North America and Europe. Even though uncommon, this parasitic larva can cause severe destruction of internal eye structures and lead to total blindness, if Ophthalmomyiasis Interna is not managed promptly

Who gets Ophthalmomyiasis Interna? (Age and Sex Distribution)

• Ophthalmomyiasis Interna is a very rare fly larvae infestation that may occur in individuals of any age group
• Both males and females are affected
• Worldwide, individuals of all racial and ethnic groups may be affected. Geographically, many cases are reported from Europe, North America, and northern parts of Asia 

What are the Risk Factors for Ophthalmomyiasis Interna? (Predisposing Factors)

The following are the risk factors for Ophthalmomyiasis Interna: (mainly in the endemic regions)

• Living in or visiting the endemic areas, especially rural regions
• Poor personal hygiene
• Contact with animals, such as cattle, in the endemic regions
• Pre-existent wounds or lesions around/near the eye may be a risk factor for ocular myiasis

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Ophthalmomyiasis Interna? (Etiology)

• Ophthalmomyiasis Interna is an uncommon parasitic infection commonly caused by insects known as warble flies of Hypoderma species (notably the reindeer warble fly or Hypoderma tarandi)
• The primary hosts of these insects are mostly cattle, including reindeer. Some of the other names for warble flies includes gadflies, heel flies, or bomb flies

What are the Signs and Symptoms of Ophthalmomyiasis Interna?

The signs and symptoms of Ophthalmomyiasis Interna are dependent on the eye structures that are affected. In most cases, the posterior segment of the eye is involved. Unilateral (single eye), or occasionally, bilateral (both eyes) involvement is observed.

The signs and symptoms are often severe and may include the following:

• Eye inflammation including redness and eye pain
• Hemorrhage
• Floaters
• Blind spots or scotomas
• Retinal detachment that may be mild or total
• Atrophic retinal pigment epithelium (RPE) tracts
• Scarring of eye structures; multifocal fibrous scarring
• Severely impaired vision

How is Ophthalmomyiasis Interna Diagnosed?

Ophthalmomyiasis Interna is diagnosed on the basis of the following information. The diagnostic techniques used may vary based on the specific type of causative parasite.

• Complete physical examination and a thorough medical history evaluation
• Assessment of signs and symptoms
• Laboratory tests: Blood tests, such as complete blood count, which may show increased white blood cells
• General eye exam
• Slit-lamp examination
• Visual acuity test using a special and standardized test chart (Snellen chart)
• B-scan ultrasonography: Special ultrasound scan of the eye through a non-invasive diagnostic tool, to assess health of eye structures
• Optical coherence tomography (OCT) of eye: It is an ocular imaging technique to visualize the eye structure

A differential diagnosis to eliminate other conditions/infections may be considered, before arriving at a definitive diagnosis. These may include:

• Anterior uveitis
• Cavernous sinus thrombosis
• Chorioretinitis
• Endophthalmitis
• Orbital cellulitis
• Panuveitis
• Retinal detachment

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Ophthalmomyiasis Interna?

The complications of Ophthalmomyiasis Interna may include:

• Severe emotional stress
• Severe pain and discomfort; severe bleeding
• Secondary infection of the eye
• Complete detachment of the retina
• Choroidal neovascularization
• Glaucoma
• Severe fibrovascular scarring of the eye
• Cellulitis: Skin infection that involves the deeper skin tissues
• Severe inflammatory response to dead larvae or parts of larvae, especially during its removal
• Sepsis, which can be life-threatening

How is Ophthalmomyiasis Interna Treated?

The treatment for Ophthalmomyiasis Interna may involve the following measures:

• Laser photocoagulation to destroy the larvae
• Oral medications (ivermectin), if needed

Examination and identification of the larva following removal may be undertaken.

How can Ophthalmomyiasis Interna be Prevented?

Ophthalmomyiasis Interna may be prevented by considering the following measures:

• Maintaining basic personal and community hygiene and proper sanitation is highly important, particularly in the endemic zones
• Extra care should be taken while travelling to the endemic regions
• Washing hands after handling farm animals, especially cattle
• Use insect repellents to prevent the insects from entering residences
• The growth of adult flies must be effectively controlled and methods for eradication followed on a regular basis

What is the Prognosis of Ophthalmomyiasis Interna? (Outcomes/Resolutions)

The prognosis of Ophthalmomyiasis Interna varies from one individual to another.

• Successful outcomes depend upon speedy diagnosis and effective treatment of the condition
• A delayed diagnosis can result in severe complications including irreversible vision loss in the affected eye

Additional and Relevant Useful Information for Ophthalmomyiasis Interna:

The following DoveMed website link is a useful resource for additional information:

https://www.dovemed.com/healthy-living/skin-disorders/