Overview
- Definition
- Ocular infestation involving obligate parasitic botfly larvae (order Diptera) via direct inoculation
Ophthalmomyiasis externa – eyelid and adnexa
Ophthalmomyiasis interna – intraocular (rare)
Requires animals (sheep, cows, rabbits or rodents) as hosts to complete developmental cycle, and larvae are subsequently passed to humans most commonly via the conjunctival surface directly
Larvae mouth hooks and thorax spines result in mechanical injury to eye
Can migrate throughout anterior and posterior structures, may avoid examination light
Death of parasite can result in ocular inflammation
- Symptoms
Tearing
Eyelid twitch
Irritation
Redness
Mild blurring
- Laterality
Unilateral
- Course
Indolent
- Age of onset
All age groups affected
- Gender/race
No gender or racial predilection
Worldwide
- Systemic association
None
Exam: Ocular
Anterior Segment
Motile larvae often seen on conjunctival cul-de-sac or cornea
Conjunctivitis – Hyperemic with hemorrhages, and follicles
Keratitis
Posterior Segment
Direct visualization of larvae
Subretinal tracks where larvae have traveled
Vitreous hemorrhage
Retinal detachment
- Endophthalmitis (rare)
Chorioretinitis, purulent panuveitis (usually results from death of larvae)
Exam: Systemic
None
Imaging
FA: reveals extent of mechanical injury to RPE and macula via window defects, scarring
OCT: Intraretinal and subretinal tunnels can be visualized Fundus Photo: White lines often present to show path of tunnels
Laboratory and Radiographic Testing
Examine removed maggot in fixative to identify species
Differential Diagnosis
Diffuse unilateral subacute neuroretinitis (DUSN)
Angioid streaks
Traumatic choroidal ruptures
Histoplasmosis
Treatment
Remove larvae from the ocular surface at slit lamp with topical anesthetic, immobilizing maggot
- Curative and definitive treatment is surgical removal from internal ocular structures
Argon laser to kill maggot, but parasite still needs removal via pars plana vitrectomy to avoid inflammatory reaction
Topical and oral steroids to control inflammation
Referral/Co-management
Infectious Disease