Exophthalmos Associated With Pathological Dilation of the Sinus Orbitalis in Two Green Iguanas ( Iguana iguana )

OBJECTIVES: To describe the clinical presentation, diagnostic and therapeutic approach of exophthalmos secondary to pathological dilation of the sinus orbitalis (SO) in two green iguanas (Iguana iguana). ANIMALS STUDIED: Two unrelated, adult green iguanas presented with unilateral exophthalmos. Case 1 was presented with chronic, irreversible ocular lesions secondary to exophthalmos at admission to a reptile shelter. Case 2 was a client-owned iguana with a three-week history of progressive periocular swelling and hyporexia. PROCEDURES: Both iguanas underwent physical and ophthalmological examinations and orbital ultrasonography. Necropsy was performed in Case 1, and computed tomography (CT) was performed in Case 2. RESULTS: In both cases, imaging demonstrated pathological unilateral SO dilation associated with impaired venous outflow due to presumed intravascular thrombosis, resulting in unilateral exophthalmos. In Case 1, the left SO contained a thrombus occupying ~70% of its volume. The presence of corneal perforation and iris prolapse necessitated transpalpebral enucleation of the left eye. As the iguana failed to adapt to monocular vision, euthanasia was performed. In Case 2, exposure keratoconjunctivitis of the right eye and uveitis were present. Contrast-enhanced CT confirmed marked dilation of the right SO with a caudal intraluminal filling defect consistent with focal thrombus formation. Aspiration of the SO resulted in resolution of exophthalmos, with complete recovery and no recurrence during one-year follow-up. CONCLUSION: Pathological dilation of the SO secondary to impaired venous outflow from thrombosis or coagulum formation may represent an underrecognized etiology of exophthalmos in green iguanas, potentially associated with repetitive rostral trauma incurred during defensive head-striking behavior.