Sight loss caused by diabetic retinopathy. Street scene as it would appear to a patient with diabetic retinopathy, or haemorrhaging of the blood vessels in the retina. The retina is the light-sensitive membrane lining the back of the eye. Blood spots from the burst blood vessels accumulate on the retina and obscure the vision, and if left untreated the condition leads to complete blindness. However, it can be treated effectively with laser surgery or vitrectomy. During vitrectomy, the watery vitreous that fills the eyeball is removed and replaced with a saline solution. For an image showing how someone with normal sight would view this scene see P420/596.