A 58-year-old woman with poorly controlled type 2 diabetes presents with a 2-day history of progressive loss of vision in her right eye, described as 'floaters' followed by a 'curtain falling'. She denies pain. On examination, visual acuity is counting fingers in the right eye and 6/9 in the left. Fundoscopy of the right eye is difficult due to vitreous opacity. What is the most likely diagnosis?