Proliferative diabetic retinopathy (PDR) is the advanced stage of diabetic eye disease, which damages the blood vessels of the retina—the light-sensitive tissue at the back of the eye. PDR is defined by neovascularization, the growth of new, abnormal blood vessels. This stage follows an earlier, non-proliferative phase and carries a high risk of vision loss. These fragile vessels are the eye’s flawed attempt to fix poor circulation caused by diabetes, but their weakness can lead to serious, sight-threatening complications.
Pathophysiology of Proliferative Diabetic Retinopathy
The journey to PDR begins with its precursor, non-proliferative diabetic retinopathy (NPDR). In NPDR, persistently high blood sugar levels damage the delicate capillaries that supply the retina. This damage causes the vessel walls to weaken, leak, and eventually become blocked. As more vessels are blocked, circulation to the retina is compromised, leading to a state of oxygen deprivation known as retinal ischemia.
In response to this lack of oxygen, the ischemic retinal tissue releases signaling proteins to try and restore its blood supply. A key protein in this process is Vascular Endothelial Growth Factor (VEGF). The release of VEGF triggers the growth of new blood vessels, marking the transition from the non-proliferative to the more advanced proliferative stage.
These newly formed blood vessels are not normal; they are fragile, grow on the surface of the retina, and are prone to bleeding. They do not effectively resupply the retina with oxygen. Instead, their structural weakness is the underlying cause of severe complications like bleeding into the eye and retinal detachment. The production of VEGF is a central driver of this process, making it a primary target for treatment.
Symptoms and Diagnostic Procedures
PDR can progress without noticeable signs until significant damage has occurred. When symptoms do appear, they can include:
- A sudden increase in floaters, which may appear as dark spots or cobwebs
- Blurry or fluctuating vision
- Dark or empty areas in your vision
- A sudden and total loss of vision
Diagnosing PDR involves a comprehensive dilated eye exam, which allows an ophthalmologist to get a clear view of the retina. During this exam, the doctor looks for signs of neovascularization. To get a more detailed picture of the retinal structure, a non-invasive imaging test called optical coherence tomography (OCT) is often used. OCT provides high-resolution, cross-sectional images of the retina, revealing its thickness and any fluid accumulation.
Another important diagnostic tool is fluorescein angiography. This procedure involves injecting a fluorescent dye into a vein in the arm. As the dye circulates, a special camera takes photographs of the retina to visualize the blood vessels. This test helps identify leaking blood vessels and areas of poor circulation, confirming the diagnosis and guiding treatment.
Associated Complications
The fragile new blood vessels that define PDR are the direct cause of several severe complications. One of the most common is a vitreous hemorrhage, which occurs when the abnormal vessels bleed into the vitreous humor, the clear gel that fills the eye. The blood clouds the vitreous, blocking light from reaching the retina and causing symptoms that range from a shower of floaters to a complete loss of vision.
As the neovascularization process continues, scar tissue can form alongside the new blood vessels on the retinal surface. This scar tissue can shrink and contract, pulling on the retina. This pulling force can cause a tractional retinal detachment, where the retina is lifted from its normal position, leading to distorted or lost vision.
A third serious complication is neovascular glaucoma. In this condition, abnormal blood vessels can grow on the iris and into the area where fluid normally drains out of the eye. This growth can block the eye’s drainage angle, preventing the aqueous humor from flowing out properly. The resulting increase in intraocular pressure can damage the optic nerve, leading to irreversible vision loss.
Medical and Surgical Interventions
Treatment for proliferative diabetic retinopathy centers on stopping the growth of abnormal blood vessels. A primary medical intervention is the use of anti-VEGF injections, delivered directly into the eye’s vitreous cavity. These medications work by blocking the action of Vascular Endothelial Growth Factor (VEGF). By inhibiting VEGF, these drugs can cause the abnormal blood vessels to shrink and reduce leakage.
Panretinal photocoagulation (PRP) is a laser surgery used to treat PDR. This procedure involves making hundreds of tiny laser burns in the peripheral retina. The treated, scarred areas require less oxygen, which in turn reduces the overall oxygen demand of the retina. This decrease helps to lower the production of VEGF, causing the new, abnormal vessels to shrink over time.
For advanced cases where significant bleeding or retinal detachment has occurred, a vitrectomy may be necessary. During a vitrectomy, a surgeon removes the blood-filled vitreous gel from the eye, clearing the visual pathway. The surgeon can also use instruments to remove scar tissue that is pulling on the retina, allowing it to settle back into its proper position.
Managing Systemic Health to Protect Vision
While direct eye treatments are necessary to manage PDR, controlling the underlying diabetes is fundamental to protecting long-term vision. The same systemic factors that contribute to retinopathy also influence its progression and treatment effectiveness. Therefore, diligent management of one’s overall health is a continuous part of preserving sight.
A primary focus is maintaining stable blood glucose levels. Working with a healthcare provider to achieve a target hemoglobin A1c (HbA1c) level can significantly reduce the risk of retinopathy worsening. Consistent blood sugar control helps to minimize the vascular damage that initiates the disease process.
Controlling blood pressure is another pillar of management, as high blood pressure can exacerbate damage to the small blood vessels in the retina. Managing cholesterol and lipid levels is also important for overall vascular health. These systemic management strategies, combined with regular eye exams, form the foundation for preventing further vision loss.