A 52-year-old woman from Mumbai with a 3-year history of treated hypertension presents to the eye clinic with a complaint of blurred vision in both eyes over the past 6 months. She denies eye pain, redness, or halos. Visual acuity is 6/9 in both eyes. Intraocular pressure is 28 mmHg OD and 26 mmHg OS on applanation tonometry. Anterior chamber angles are open on gonioscopy. Optic disc shows a vertical cup-to-disc ratio of 0.65 OD and 0.6 OS with generalized pallor and inferior notching of the neuroretinal rim. Automated perimetry reveals a superior nasal step defect in the right eye and a generalized depression in the left eye. Fundus photograph shows no retinal nerve fiber layer defects visible. What is the most appropriate initial management?