June 5, 2007 at 7:25 PM CDT - Updated July 26 at 9:05 AM
In proliferative diabetic retinopathy (PDR), abnormal blood vessels and scar tissue grow on the surface of the retina and also attach firmly to the back surface of the vitreous. The vitreous then pulls on the scar tissue and can cause the retinal blood vessels to bleed into the vitreous cavity (called vitreous hemorrhage). This can cause immediate and severe visual loss. Often, the hemorrhage will clear by itself. It if doesn't clear, a vitrectomy can be performed to remove the blood-filled vitreous.