What causes diabetic retinopathy?

Diabetes mellitus (also simply called diabetes) is characterized by an altered metabolism of carbohydrates and lipids, resulting in a chronic elevation in blood sugar (hyperglycemia). Hyperglycemia can lead to long-term changes in the circulatory and nervous systems in the body. The hyperglycemia experienced by diabetics is related to an inability to produce sufficient insulin, a resistance to the effects of insulin, or both.



The diagnosis of diabetes is made based on a person's fasting plasma glucose (FPG) levels, (commonly referred to as the fasting blood sugar). An FPG level of 126 mg/dL or higher indicates the presence of diabetes mellitus.



Diabetic retinopathy is a complication of diabetes in which the tiny blood vessels in the retina are damaged by the disease. Damage to the retinal blood vessels can cause a number of problems. In some cases, the damaged blood vessels leak fluid and lipids under the macula, the most sensitive part of the retina that allows us to see details. The fluid causes the macula to swell, blurring vision. In other cases, the retinal blood vessels can become blocked, causing portions of the retina to cease functioning because of lack of oxygen and nutrients.

In its advanced stage, diabetic retinopathy is characterized by the growth of fragile blood vessels along the retina and into the clear, gel-like vitreous that fills the inside of the eye. These tiny blood vessels can break open and bleed, causing vision to be obscured and permanent damage to the retina.