Diabetes is a very common disease in the United States, characterized by abnormally high blood glucose, and is associated with a variety of complications. Although the full list of complications associated with diabetes is outside the scope of your question, an important potential complication of diabetes is damage to the back of the eye, called the retina. The retina is important in receiving incoming light and sending signals back to the brain, where an image is produced. Damage to the retina in patients with diabetes, called "diabetic retinopathy", is due to direct damage to the walls of the blood vessels of the eye, and can lead to visual loss or blindness.
All diabetic patients should have yearly screening of their retina to look for diabetic retinopathy. The reason for screening is that, if diabetic retinopathy is diagnosed, there are excellent therapeutic options that will prevent visual loss. There are a variety of options for how to diagnose diabetic retinopathy, which include visual testing, examination of the back of the eye with an ophthalmoscopy (eye microscopy), and "slit-lamp" examination with a special microscope. One such diagnostic method is electroretinography, which measures the response of the back of the eye (the "retina") to various light stimuli. Only a trained ophthalmologist
or "eye doctor
" can decide which of these diagnostic options is appropriate for testing for diabetic retinopathy, but your doctor is correct that, as a diabetic, a routine yearly eye exam is a crucial part of your care.