Primary Orbital Hydatid Cyst

The authors want to highlight the importance of clinical, radiological and histopathological evaluation in unilateral proptosis. A 17-yearoldmale presented with left progressive nonpulsatile proptosis, lateral gaze diplopia and decreased visual acuity. It was diagnosed asorbital hydatid cyst on CT scan and MRI. The patient was successfully operated with near total recovery of the vision. Radiologicalinvestigation showed a circumscribed cystic lesion lateral to orbit separate from the lacrimal gland. Intraoperative cysts and postoperativehistopathology confirmed the primary orbital hydatid cyst.Although rare there is always a possibility of a primary hydatid in patients with unilateral proptosis, restricted eye movements andlateral decreased visual acuity. This is possible even when the Casoni�s test is negative. Surgical excision with postoperative albendazoleis the effective treatment for the cure of disease.