A 38-year-old woman from Bangalore presents with a 6-month history of burning pain in the right V1 (ophthalmic) distribution, accompanied by conjunctival injection and lacrimation. Pain is constant, not lancinating, and does not respond to carbamazepine 800 mg/day. MRI brain shows no mass or demyelination. She has a history of recurrent oral ulcers and uveitis. What is the most appropriate next step in management?