Diffuse unilateral subacute neuroretinitis: a case of mistaken identity.

Background: The report details a case of diffuse unilateral subacute neuroretinitis (DUSN) wherein a subretinal parasite was visualized and subsequently destroyed with laser photocoagulation.
Methods: Full historical and serologic investigations were carried out. A literature search to determine all possible causes of DUSN was also completed.
Results: Serologic results supported Baylisascaris procyonis as the cause of infection, but imaging of the worm before destruction did not support this organism as the etiologic agent. On the basis of morphologic evaluation of still imaging and videoimaging, patient exposure information, and known causes of DUSN, the infection was likely due to Alaria species, providing further evidence of a trematode cause.
Conclusions: The report adds to the literature that trematodes should be recognized as a possible cause of ocular larva migrans. Although laser therapy is appropriate and effective for both nematode and trematode infections of the eye, in the case of adjunctive medical therapy, identification of the parasite group is essential.