Diffuse unilateral subacute neuroretinitis. 
In patients with diffuse unilateral subacute neuroretinitis (DUSN), the presence and, therefore, clinical visualization of subretinal nematode makes the diagnosis obvious.  However when located under the retinal pigment epithelium (RPE), diagnosis is presumptive and challenging.  We report a case of presumed DUSN to illustrate this diagnostic dilemma and to highlight the clinical signs which suggest the diagnosis.  Case report of a patient with DUSN.  In our patient the nematode was not located subretinally and this made the diagnosis difficult.  However, the appearance of sub-RPE serpiginous tract in the infero-temporal retina, peripheral RPE hypopigmentation and good clinical response to anti-helminthics supported the diagnosis.  It is important to have a high index of suspicion when patients present with a combination of above findings.  This will help in early control of ocular inflammation and salvaging vision.