Description

• Noninflammatory retinal disorder characterized by retinal capillary closure and microaneurysms. Retinal ischemia leads to release of a vasoproliferative factor, stimulating neovascularization (NV) on retina, optic nerve, or iris.
• Most patients with diabetes mellitus (DM) will develop diabetic retinopathy (DR). It is the leading cause of new cases of legal blindness among residents in the United States between the ages of 20 and 64 years.
• DR can be divided into three stages:
  • Nonproliferative (NPDR) (background)
  • Severe NPDR (preproliferative)
  • Proliferative (PDR)

Pregnancy Considerations

• Pregnancy can exacerbate condition.
• Pregnant diabetic women should be examined in 1st trimester and then every 3 months until delivery.

Epidemiology

Incidence

• Peak incidence of type 1, juvenile-onset DM is between the ages of 12 and 15 years. In type 1 DM (T1DM), there is β-cell destruction, leading to insulin deficiency.
• Peak incidence of type 2, adult-onset DM is between the ages of 50 and 70 years. Type 2 DM (T2DM) ranges from a condition characterized by insulin resistance with relative insulin deficiency to one that is predominantly an insulin secretory defect with insulin resistance.
• Incidence of DR is directly related to the duration of diabetes.
• <10 years of age, it is unusual to see DR, regardless of DM duration.

Prevalence

• 13.0% of all U.S. adults, 18 years or older, have DM. Prevalence increases with age, reaching 26.8% of U.S. adults aged >65.
• Worldwide, DR affects 1 out of 3 persons with DM.
• Predominant age:
  • Risk increases after puberty.
  • 2/3 of T1DM patients who have had DM for at least 35 years will develop PDR, and 1/3 will develop diabetic macular edema (DME). Proportions are reversed for T2DM.
• Predominant sex: male = female (T1DM); female > male (T2DM).

Etiology and Pathophysiology

• Related to development of diabetic microaneurysms and microvascular abnormalities
• Reduction in perifoveal capillary blood flow velocity, perifoveal capillary occlusion, and increased retinal thickness at the central fovea in diabetic patients are associated with visual impairment in patients with DME.
• Vascular endothelial growth factor (VEGF) is elevated in patients with hypoxic retina. Intraocular levels of VEGF are elevated in patients with retinal or iris NV. Retinal hypoxia also contributes to DME, and VEGF is a major contributor to DME.

Risk Factors

• Duration of DM (usually >10 years)
• Poor glycemic control
• Pregnancy
• Renal disease
• Systemic hypertension (HTN)
• Smoking
• Elevated lipid levels
• Myopic eyes (eyes with longer axial length) have a lower risk of developing DR and of its progression.

General Prevention

• Monitor and control of blood glucose.
• Schedule yearly ophthalmologic eye exams.

Commonly Associated Conditions

• Glaucoma
• Cataracts
• Retinal detachment
• Vitreous hemorrhage (VH)
• Disc edema (diabetic papillopathy); may occur in T1DM and T2DM