Delusional parasitosis presenting with ocular formication

To the Editor

Delusional parasitosis involving the eye is uncommon, with Meraj et al. (2011) noting six case reports in the published literature. We present the case of a 63-year-old male with no previous psychiatric history who required hospitalisation with near-blindness and the bizarre belief that ants were incessantly crawling on his skin and, more distressingly, on his eyes.

In the 6 months preceding hospitalisation, he reported ‘bugs’ crawling on his skin (i.e. formication). Accordingly, he was twice treated for scabies by his general practitioner. He travelled to the Philippines – his usual residence for 6 months of the year. There, his symptoms worsened such that he began spending excessive periods of time washing himself with a 70% alcohol solution to ‘kill the ants’. Six weeks prior to admission, he attempted to catch the ants as evidence of an infestation. He sprayed his home and body with insecticide. In a further futile attempt to seek relief from his symptoms, he began wiping his eyes with cotton wool swabs. This proved unsuccessful. He then applied olive oil and later honey to each eye ‘to slow the ants down’. Finally, in sheer frustration, he applied a commercially available insecticide solution to both eyes. The consequent chemical and bacterial inflammatory response necessitated admission to a local hospital. When his son became aware of his father’s plight, he travelled to the Philippines to retrieve him. Upon return to Sydney, they presented to a nearby major teaching hospital.

Admission under the neurology service facilitated a thorough assessment. Examination revealed bilateral corneal ulceration and abscesses accompanied by reduced visual acuity (finger counting only). Routine laboratory studies, syphilis serology, vitamin B12 and thyroid function tests were unremarkable. Magnetic resonance imaging (MRI) of the brain excluded cerebral pathology.

A formal ophthalmology review favoured conservative management with topical antibiotic therapy. Psychiatry consultation was sought in view of a presumptive diagnosis of delusional parasitosis. Following confirmation, he was commenced on risperidone 2 mg nocte, resulting in rapid resolution of his psychiatric symptoms. A post-discharge community psychiatry review confirmed full recovery and risperidone was weaned successfully. At 12 months following discharge, he was symptom-free.

Self-inflicted eye injuries due to psychosis are rare, with fewer than 100 cases described in the literature (Large et al., 2008). Antipsychotic medication is usually required (Large et al., 2008). Risperidone is known to perform well in this regard, with the most efficacious dose being 2 mg (Freudenmann and Lepping, 2008).