The retina is composed of nerve cells, blood vessels, and specialized photoreceptor cells, and has a core function of sensing light. Performing these functions requires energy, which in turn requires the oxygen supplied by blood vessels. When diabetes occurs, high retinal blood sugar can cause blood vessels to bleed and leak, grow irregularly, and fail to provide the retina with enough oxygen.
This in turn can cause retinal ischemia and the gradual death of retinal cells, as well as directly damaging retinal nerves. The result is blurry and distorted vision that can worsen into rapid vision loss and even retinal detachment.
Preventing diabetic retinopathy begins with maintaining average blood sugar levels below the seven percent threshold. It also involves managing cholesterol and blood pressure, although a cause and effect relationship with these conditions has yet to be proven