A 64-year-old woman with type 2 diabetes mellitus presents as she has started to bump into things since the morning. Over the previous two days she had noticed some ‘floating spots in her eyes’. Examination reveals she has no vision in her right eye. The red reflex on the right side is difficult to elicit and you are unable to visualise the retina on the right side during fundoscopy. Examination of the left fundus reveals changes consistent with pre-proliferative diabetic retinopathy. What is the most likely diagnosis?
Occlusion of central retinal vein