Proliferative Diabetic Retinopathy occurs after ischemia induces
new blood vessels ("neovascularization") to grow in an attempt to
restore circulation- these new blood vessels are weak, however, and
may cause bleeding into the eye ("vitreous hemorrhage")-
this can be associated with vision loss and scarring, with
tractional retinal detachment.
Laser treatment of the retina ("pan-retinal photocoagulation") may
induce regression of the new vessels and protect against vision loss.