Introduction:

Proliferative diabetic retinopathy (PDR) is characterized by pathologic retinal neovascularization. It can arise from the optic disc (NVD), retina (NVE) and/or the iris (NVI).

Clinical Features:

Retinal neovascularization is a hallmark of PDR, which can be seen at the slit lamp as fine networks of blood vessels extending from the retina into the vitreous cavity (Fig. 13.3.1). These vessels can cause visual loss secondary to vitreous hemorrhage, and can induce preretinal fibrosis leading to tractional retinal detachment, retinoschisis, macular edema and combined traction/rhegmatogenous RD

Neovascularization may occur at the disc or elsewhere (NVE) in the retina. It may be preceded by intraretinal microvascular abnormalities (IRMA), which represent a severe form of NPDR.

OCT Features:

The typical findings of NPDR are seen in PDR as well. In addition, NVD and NVE may manifest as loops of hyper-reflective blood vessels projecting from the retina into the vitreous, either at the disc or elsewhere (Fig. 13.3.2). In contrast, areas of IRMA are seen as disorganization of the inner retinal vascular architecture with occasional projection beyond the internal limiting membrane, but with no disruption of the hyaloid face (Fig. 13.3.3). The hyaloid may be thickened in these cases. In some cases with NVD or NVE, traction of the retina with or without retinal detachment may be seen (Fig. 13.3.4).

Ancillary Testing:

Fluorescein angiography is the most useful ancillary test in diagnosing diabetic retinopathy. FA of the areas of neovascularization shows profuse dye leakage. Ischemic areas may also be delineated on the FA.

Treatment:

PDR is treated with pan-retinal photocoagulation. As it has become clear that elevated levels of VEGF is a critical driver of neovascularization in PDR, increasingly, anti-VEGF therapy is being used as an adjunct in the treatment. There are reports that anti-VEGF injections may induce regression of PDR, but they can cause increased fibrosis of the regressing neovascularization possibly resulting in increased traction on the retina. Vitrectomy is the mainstay of therapy for non-clearing vitreous hemorrhage and traction-related complications of PDR, when pan-retinal photocoagulation fails or is not possible to perform.