A 3-year-old girl from rural Uttar Pradesh presents with her mother complaining of difficulty seeing at night for the past 2 weeks. On examination, the child has conjunctival xerosis with Bitot's spots bilaterally. Visual acuity is 6/9 in both eyes. There is no corneal involvement. The child's diet consists mainly of rice and lentils with minimal intake of green leafy vegetables or animal products. What is the most appropriate next step in management?