A 2-year-old boy from rural Maharashtra presents with leukocoria (white pupil reflex) in the right eye noted by his mother 3 weeks ago. On examination, the child is otherwise healthy with normal developmental milestones. Intraocular pressure is normal bilaterally. Dilated fundoscopy reveals a white mass arising from the retina in the right eye, with vitreous haze but no obvious extraocular extension. The left eye appears normal on examination. What is the most appropriate next step in management?