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Ophthalmomyiasis, maggot or fly larvae infestation of the eye, is a rare condition that can have variable presentation depending on the type of fly, the ocular structures involved, and the level of larval infiltration.
A 60 year old African-American male presented with a chief complaint of a swollen, moderately painful red right eye since 4 am that day. Ocular history was significant for foreign body lid trauma of unknown aetiology (presumably a rock or insect) 2 days earlier while riding his motorcycle without protective goggles.
Ocular examination revealed 20/20 vision in each eye with correction. Pupils, extraocular motilities, and confrontation fields were normal. Slit lamp evaluation revealed upper and lower lid oedema with mild erythema in the right eye. A 1.5 mm round ulcerated lesion was noted on the right outer canthal region that appeared to pulsate as the patient was examined in the slit lamp (fig 1). The left eye and other ocular structures in the right eye were unremarkable.
Upon external digital pressure of the ulcerated lesion, a foreign organism was seen to retreat into the ocular tissue. Manual forceps were used to remove a 1.0 cm long white segmented maggot (fig 2). This specimen was identified by an entomologist under a microscope, as being of the Calliphoridae family, Phaenicia lucilia, otherwise known as a screwworm fly.
The patient was given erythromycin ointment for use twice a day over the lesion. After 3 days, the patient returned with complete resolution of the lid oedema and erythema (fig 3).
Ophthalmomyiasis is generally caused by sheep botflies and flesh flies. The most commonly reported organism in the literature is Oestrus ovis, a botfly highly prevalent in sheep herding and farming communities.1,2 These flies typically lay their eggs on decaying organic material, but are also attracted to open mucopurulent human sores. Within 24 hours, these eggs hatch, producing larvae which then feed on human tissue.2,3 This case was somewhat unusual in that trauma was the mechanism by which the fly eggs were deposited. Clinical features of external ophthalmomyiasis can include conjunctivitis, conjunctival hemorrhage, corneal abrasion, and iritis. Internal ophthalmomyiasis can produce vitreous haemorrhage, tractional retinal detachment, endophthalmitis, and hypopigmented linear and arcuate subretinal tracks. Some of the cases of presumed internal ophthalmomyiasis have been based on hypopigmented subretinal tracks without documentation of an actual maggot.1
Treatment strategies depend upon the type of ocular involvement and the level of damage. In cases of external ophthalmomyiasis, manual forceps removal of the larvae is ideal. Ophthalmic ointment can be used to block the larvae’s respiratory pore, thereby suffocating the organism to facilitate manual removal. Treatment strategies in cases of internal ophthalmomyiasis are case specific, ranging from iridectomy, vitrectomy, and retinotomy to laser photocoagulation. This is the first reported case of ophthalmomyiasis externa by a screwworm fly, Calliphoridae Phaenicia sp successfully treated with manual forceps removal.
Thanks to Kipling Will and David Faulkner for their assistance from the University of California, Berkeley, Entomology Department. Thanks to A Bitanga for the photographs. Thanks also to Thomas Lietman for his help with the manuscript.