A 52-year-old man from Delhi presents with a 3-week history of progressive visual field loss. On examination, he has a dense superior altitudinal defect in the right eye, with normal intraocular pressure (14 mmHg) and a healthy optic disc appearance. Fundoscopy reveals no pallor, cupping, or signs of retinal pathology. Visual acuity is 6/6 in both eyes. What is the most appropriate next step in management?