MSFinals-3875

An 80-year-old man presents to the clinic with an 8-month history of uncorrectable poor vision. He has a medical history of hypertension, allergic conjunctivitis, and type 1 diabetes mellitus, and has been a heavy smoker for the past 20 years. On examination, his right eye has a visual acuity of 6/30 while the left eye is normal. Fundoscopy reveals increased retinal blood vessels, blot haemorrhages, and hard exudates in the nasal upper quadrant of the right eye. He denies any sudden visual loss or ocular trauma. What is the most likely diagnosis?