Intraocular microfilariae can be seen in the anterior chamber. Dead microfilariae are usually seen in the cornea (especially peripherally).
Other ocular features are punctate keratitis and sclerosing keratitis; anterior uveitis, usually of the nongranulomatous type with loss of the pigment frill, and posterior synechiae are common. Secondary cataract and glaucoma can develop.
Chorioretinitis of the chronic nongranulo-matous type can occur, with secondary degenerative changes in the retinal pigment epithelium (RPE) neuroretina and the chorio-capillaries. There might be granular atrophy of the RPE, subretinal fibrosis, retinal arteriolar attenuation and vasculitis. Optic atrophy and neuropathy are not uncommon.
Diagnosis is confirmed by skin snip and the Mazzoti test, which depends on a Herxheimer reaction to a single dose of diethylcarbamazine. Care is required with this test because the reaction could be severe.
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