A 35-year-old woman from Mumbai with a 6-month history of recurrent painful oral ulcers and genital ulceration presents with acute loss of vision in the left eye over 3 days. On examination, visual acuity is hand motions. Slit-lamp shows severe anterior chamber reaction (4+ cells), fibrin, and posterior synechiae. Fundoscopy reveals dense vitritis with hemorrhage obscuring the disc, and multiple retinal infiltrates with vasculitis. B-scan ultrasonography confirms severe vitritis. Serum HLA-B51 is positive. What is the most appropriate initial management?