A 65-year-old female has sudden blurring and darkening of her vision in the right eye and sees multiple dark streaks. K/C/O type 2 diabetes mellitus and migraine. Ophthalmologic examination shows visual acuity of 20/40 in the left eye and 20/100 in the right eye. The fundus is obscured and difficult to visualize on fundoscopic examination of the right eye. The red reflex is diminished on the right. The most likely diagnosis is?