Sir,

Case report

A 34-year-old caucasian man attended eye casualty complaining of unilateral left upper lid swelling, which had occurred over a 24-h period. On examination visual acuity was 20/20 in both eyes with marked left upper lid oedema and minimal papillary reaction. Anterior segment examination, intraocular pressures, and fundoscopy of both eyes were unremarkable. A diagnosis of allergic preseptal oedema was made and the patient was prescribed a topical antihistamine.

An hour later the patient returned to eye casualty, anterior segment examination at this second attendance identified a translucent worm under the temporal bulbar conjunctiva (Figure 1a). On direct questioning the patient reported a visit to rural Cameroon 12 years previously, where he had explored an uncharted river. Under topical anaesthesia (Tetracaine 0.5%), the subconjunctival worm was removed and microscopy identified an adult 4 cm female loa loa worm (Figure 1b). Blood analysis demonstrated a peripheral eosinophilia of 1.52 × 109/l and a microfilarial load of 2000/ml. The patient was treated with albendazole 400 mg twice daily for 21 days, his ocular symptoms resolved within 2 days of commencing therapy.

Figure 1
figure 1

(a) A frontal photograph showing left periorbital swelling. (b) Anterior segment appearance showing a subconjunctival filarial nematode loa loa.

Full size image

Loa loa is a filarial nematode endemic in the rain forest regions of West and Central Africa. The nematodes are transmitted by Chrysops flies and upon infection many patients remain asymptomatic for up to 17 years. The adult worms move through the subcutaneous tissues often appearing transiently at the eye, where uveitis, cataract, and exudative retinal detachment have been reported.1, 2, 3, 4, 5 Life-threatening complications including cardiomyopathy, encephalopathy, nephropathy, and pleural effusion may occur. Definitive diagnosis may be made following histological examination of the loa loa worm or microfilaraemia. In addition, patients require skin biopsy to exclude coexistent onchocerciasis. The global treatment of choice is chemotherapy with diethylcarbamazepine; however, albendazole is used in the UK as a result of licensing restrictions.2, 3 Removal of the subconjunctival worm is not essential; however, it may lead to the diagnosis and relieves ocular irritation. In an era of increasing global travel, this case highlights the importance of direct questioning of previous travel as signs may be nonspecific and transitory.