Toxocara canis.

Toxocara canis, commonly known as the dog ascrid, is a frequent parasite of the domestic dog. If the eggs of an adult worm are accidentally ingested by a human host, usually a child, a larval form of the worm develops that can survive for a limited period in various human tissues. The retina is one of these tissues and upon the death of this organism a granulomatous reaction occurs and a fibrotic mass is formed in the retina. This unusual ophthalmoscopic appearance is demonstrated by the presentation of three fundus photographs of patients with suspected Toxocara lesions. A knowledge of this parasite and its life cycle will aid in its recognition, treatment, and possible prevention.