A 6-year-old boy from rural Odisha is brought to the emergency department with sudden loss of vision in the right eye over the past 6 hours. On examination, visual acuity is hand movements in the right eye and 6/6 in the left. The right eye shows a hazy cornea with central corneal ulceration and stromal infiltration. Conjunctival xerosis and Bitot's spots are visible bilaterally. There is a history of measles infection 3 weeks ago. What is the most likely diagnosis, and what is the immediate management priority?