An 80-year-old man presents with a one-year history of gradual, painless blurring of his central vision in both eyes. He finds reading and recognising faces increasingly difficult. He also reports that straight lines, like door frames or telegraph poles, sometimes appear wavy or distorted (metamorphopsia). Funduscopic examination reveals yellowish deposits (drusen) and some areas of pigmentary change clustered around the fovea in both eyes. Peripheral visual fields appear intact. What is the most likely diagnosis?