Abstract
<title>Abstract</title> <p> Background <italic>Loa loa</italic> infection is endemic in parts of Central and West Africa but is rarely encountered in China. In non-endemic settings, ocular migration of an adult worm may be the first specific clue. Recognition is important because blood smears can be negative and unsupervised antiparasitic treatment may be unsafe when the microfilarial burden is unknown. Case presentation: A 44-year-old man from Yanbian Prefecture, Jilin Province, presented with a 1-day history of a moving foreign-body sensation at the medial aspect of the right eye. He had lived and worked in Gabon for five years and returned to China approximately two months before presentation. Slit-lamp examination showed a motile, transparent, filiform organism beneath the right bulbar conjunctiva, with conjunctival injection but no corneal, anterior-chamber, vitreous or fundus abnormality. Peripheral eosinophilia was marked, with an eosinophil count of 3.73 × 10 <sup>9</sup> /L and an eosinophil percentage of 34.7%. Cranial magnetic resonance imaging, chest computed tomography, ocular B-scan ultrasonography and abdominal ultrasonography did not show extraocular involvement. Daytime and nocturnal thick and thin blood smears were negative for microfilariae. Treatment and outcome: The worm was removed intact under topical anesthesia through a small conjunctival incision. Morphological examination showed a whitish, cylindrical filarial worm approximately 50 mm long and 0.5 mm wide, with cuticular bosses and intrauterine sheathed microfilariae, consistent with an adult female <italic>L. loa</italic> . Postoperative topical antibiotic and steroid therapy was given. The patient remained stable after surgery and later reported self-administration of ivermectin obtained abroad. Conclusion In a patient with relevant Central African exposure, visible subconjunctival worm migration plus eosinophilia is highly suggestive of ocular loiasis even when blood smears are negative. This case highlights the value of a travel-history-driven ophthalmic examination, careful parasite preservation and supervised systemic evaluation after extraction. </p>