Diabetic retinopathy represents the major ocular complication of diabetes. It occurs in an estimated 40% of patients with diabetes, and in 20% this retinopathy will become vision-threatening.
The longer the duration of diabetes, the more likely the development of diabetic retinopathy and the greater its severity. In persons with type 1 diabetes, diabetic retinopathy is nearly universal 20 years post diagnosis, while in persons with type 2 diabetes, the incidence of retinopathy exceeds 60% 20 years post diagnosis
It has been observed that nearly every person diagnosed with diabetes before age 30 will develop retinopathy within 20 years of diagnosis. Retinopathic damage will already have occurred in approximately 5% of patients diagnosed with diabetes by age 30.
Many individuals will have experienced visual loss secondary to diabetic retinopathy before their systemic disease is diagnosed and treated. In fact, an estimated 20% of those newly diagnosed with type 2 diabetes already have signs of diabetic retinopathy at the time of diagnosis. In these patients, it may actually be the retinopathy that leads to the diagnosis of diabetes.
Characteristics of Ocular Damage Related to Retinopathy
Pathophysiologically diabetic retinopathy is characterized by microvascular leakage and microvascular occlusion. These processes lead to capillary dropout (the vessels become so blocked that they can no longer transport blood and oxygen), development of microaneurysms, vascular occlusion and/or hyperpermeability, and neovascularization. The vision loss and blindness resulting from diabetic retinopathy are usually due to vascular leakage or ischemia.
Stages of Diabetic Retinopathy
The Clinical Diabetic Retinopathy Severity Scale divides DR into two stages: non-proiferative (NPDR) and proliferative (PDR).
- Non-proliferative retinopathy is characterized by venous beading, microaneurysms, retinal hemorrhage, hard exudates, and diabetic macular edema (DME); it is subdivided into mild, moderate, and severe categories.
- Proliferative diabetic retinopathy results from profound and persistent retinal ischemia; its clinical manifestations include retinal and vitreous hemorrhage, neovascularization of the retina and optic nervehead, retinal scarring and fibrosis, and traction retinal detachment (RD).