This month we will begin our discussion about diabetes and diabetic eye disease.
Diabetes affects millions of people worldwide. In 2015, it was estimated that approximately 30.3 million people were affected in the U.S. alone (www.cdc.gov/diabetes). Diabetes can affect every part of our body and the eyes are no exception. As we reviewed in the anatomy of the eye, there are many structures that can be affected by diabetes.
We will begin our discussion on the impact on the retina, then move onto other ocular structures that can be affected by diabetes.
What is diabetes?
Our discussion will focus on the effects of diabetes mellitus (DM). After eating, food is broken down into several compounds including sugar. When sugar levels go up in the blood, the pancreas produces a hormone called insulin to remove it and deliver it to cells in the body. In diabetes, the blood sugar remains elevated. Either the body does not make enough insulin (type 1 DM), or the body cannot use the insulin that is produced (type 2 DM).
There are other forms of diabetes. Gestational diabetes occurs during pregnancy in women who have never had diabetes. The term prediabetes is used for people who have high blood sugar but do not meet all the criteria to be diagnosed with diabetes.
How is diabetic eye disease in the retina defined?
Diabetic retinopathy (DR) and diabetic macular edema (DME) are the retina-related changes in diabetic eye disease. In diabetic retinopathy, the blood vessels of the retina are affected. This is further separated into non-proliferative and proliferative disease. Diabetic macular edema is a consequence of diabetic retinopathy. It is swelling or a collection of fluid in the center of the retina called the macula.
This month we will focus on non-proliferative diabetic retinopathy (NPDR).
What puts people at higher risk of developing non-proliferative diabetic retinopathy?
Chronically elevated sugar in the body damages the blood vessels in the retina leading to diabetic retinopathy. This damage to the blood vessels can cause them to leak fluid or blood. The risk also increases the longer one has diabetes.
What are the symptoms?
All forms of diabetic eye disease can cause vision loss and blindness. The early stages often do not produce any symptoms. NPDR is usually diagnosed on routine eye exam or when the vision is affected. This can be in the form of blurry vision, distortions, or cloudy vision.
How is it detected?
A comprehensive exam including checking the vision and dilating the eyes to view the retina are imperative to diagnose NPDR. Photos are taken to monitor the progression of the disease.
Mild non-proliferative diabetic retinopathy shows small outpouchings of the vessels called microaneurysms.
Moderate non-proliferative diabetic retinopathy shows focal areas of bleeding from the blood vessels.
Severe non-proliferative diabetic retinopathy is where blood vessels sustain more damage, become blocked, and are unable to provide enough nutrition to the retina.
Very severe non-proliferative diabetic retinopathy is further progression of disease and shows several characteristics of blood vessel damage.
Other photos taken during an exam are to determine the severity of disease. Optical coherence tomography, OCT, looks for macular edema and fluorescein angiography, FA, looks for damaged and leaking blood vessels. FA involves injecting a dye into the arm and taking photos as the dye goes through the blood vessels in the eyes. More on these in the next few months.
The photo below shows an FA of a patient with severe NPDR. The arrow shows an area of poor blood supply where the retina is not getting enough nutrients.
What are the treatments for non-proliferative diabetic retinopathy?
Prevention: Often changes can occur in the eyes without the person knowing. It is very important to get a dilated comprehensive exam once a year to look for changes. If retinopathy is detected, often the exams are more frequent.
Controlling sugar, BP, and cholesterol: Studies have shown that maintaining normal sugar levels, blood pressure, and cholesterol reduce the risk of developing eye disease and vision loss. The hemoglobin A1c is used to determine sugar levels over a three-month period. A lower A1c reduces the risk of developing retinopathy.
Lifestyle modifications: Smoking and obesity are risk factors for diabetes and therefore play a role in diabetic eye disease as well.
Laser: Most cases of NPDR do not require treatment. However, some doctors will treat the later stages of severe and very severe with laser. Panretinal photocoagulation (PRP) involves making small burns in the retina to treat the abnormal blood vessels and prevent them from bleeding.
Low vision tools: There are many aids to help patients with poor vision from diabetic retinopathy including magnifiers, high-powered lenses, large print materials, talking clocks and calculators, closed-circuit televisions, and computer-based aids.
Return next month to continue our discussion on diabetic eye disease!