Iridal melanoma in the right eye of a dog: A rare case from Chonburi, Thailand.

Background: In dogs, intraocular tumors are uncommon and often present with nonspecific clinical signs such as vision loss, corneal opacity, or hyphema. Melanocytic tumors of the iris are rare among these, with limited documentation in Thailand. Accurate diagnosis requires ophthalmic examination, imaging, and histopathology, whereas treatment strategies depend on tumor location and progression. Case Description: A 16-year-old neutered male Shih Tzu presented with progressive blindness and a history of bumping into objects. Ophthalmic examination revealed blood-tinged discharge, elevated intraocular pressure (99 mmHg) in the right eye (OD), and a superficial corneal ulcer. Ocular ultrasonography using B-mode at 8 MHz demonstrated iris thickening and a hypoechoic intraocular mass. Hematology revealed thrombocytopenia and eosinophilia. Surgical enucleation of the OD was performed, and histopathology confirmed iridal melanoma. Postoperative recovery was uneventful, and the surgical wound had healed normally at the 1-month follow-up. The dog remained bright and maintained a normal appetite. No abnormalities were observed in the contralateral iris. Conclusion: This is a rare and unusual case of thrombocytopenia and eosinophilia with iridal melanoma in a dog in Thailand. Comprehensive ophthalmic examination, including ultrasonography, plays a crucial role in dogs with elevated intraocular pressure and intraocular hemorrhage. Enucleation was effective in resolving clinical signs and preventing recurrence in this older dog. Ongoing monitoring of the contralateral eye and potential metastatic neoplasia in other organs is essential.