A 66-year-old man with a 15-year history of Type 2 Diabetes presents complaining of gradually worsening blurred vision in both eyes over the past year. He denies any eye pain. Fundoscopy reveals multiple microaneurysms, dot and blot haemorrhages, and hard exudates clustered around the fovea in both eyes. Visual acuity is 6/12 bilaterally. What is the most likely diagnosis explaining his visual symptoms?