The hallmark of proliferative diabetic retinopathy is:

• A. Macular edema
• B. Retinal detachment
• C. Vitreous hemorrhage
• D. New blood vessel growth

Answer: (D)

The defining sign of proliferative diabetic retinopathy is the growth of new, abnormal blood vessels on the retina and optic disc (neovascularization). This occurs in response to retinal ischemia and is what differentiates proliferative from nonproliferative stages. These fragile vessels can bleed into the vitreous and, with scar tissue formation, can pull on the retina to cause tractional detachment, both of which can lead to serious vision loss.

Macular edema can occur in diabetic retinopathy but is not the hallmark of the proliferative stage. Retinal detachment and vitreous hemorrhage may happen as complications of neovascularization, but they are not the defining feature themselves—the new vessel growth is.