Diabetic Eye Disease 101: The Science of Blood Sugar and Vision
November is National Diabetes Awareness Month and a good time to talk about some of the complexities of the disease that affects the lives of many Americans. Diabetes is found in over 10% of the population in the US.
A person with diabetes will experience high blood sugar levels (hyperglycemia). The glucose from the food we eat needs to be transferred from the bloodstream into the cells to provide energy. A hormone called insulin usually assists this transfer. A diabetic person either produces none or not enough of this crucial hormone — and hyperglycemia can occur.
There are complications to having high blood sugar levels, and it can affect many body functions. One function that can be particularly affected is your vision. This blog will go over some of the eye diseases associated with diabetes — the causes, symptoms, and some common treatments.
The most prevalent diabetic eye disease is diabetic retinopathy. This disease occurs when the blood vessels in the retina do not receive enough nutrients over time due to chronic hyperglycemia. The retina is the film at the back of the eye that contains millions of cells that receive the light your eye takes in. These cells then transfer that information via the optic nerve to your brain for processing. This process requires a lot of energy!
There are three main stages of diabetic retinopathy.
Stage 1: Diabetes without retinopathy
The first stage is called diabetes without retinopathy. In this stage, cells on the blood vessels called pericytes are damaged. Pericytes help regulate blood flow and the loss of pericytes mean that walls of the blood vessels will start to bulge. The patient will often experience no symptoms in the first stage of retinopathy.
The best way to manage the first stage is to:
Maintain good control of blood sugar levels
Go to a yearly eye exam to monitor for progression to the second stage
Stage 2: Nonproliferative retinopathy
The second stage is nonproliferative retinopathy and usually begins 15-25 years after a diabetes diagnosis. The weakened blood vessel walls from the lack of pericyte cells will continue to bulge, creating microaneurysms. These appear as small red dots in the retina in an eye exam. Blood vessels can also leak blood, proteins, and lipids, causing hard exudates to form which appear as yellow/white “cotton wool” spots. These red microaneurysms and yellow/white hard exudates observed in an eye exam are often the first signs of diabetic retinopathy that your eye doctor will detect. This stage is sometimes asymptomatic for the patient and can last a long time before progressing to the third stage.
To manage this stage:
Continue to maintain good control of blood sugar levels
Go to a yearly eye exam to monitor progression
Maybe start taking Anti-VEGF medication (see below)
Stage 3: Proliferative retinopathy
The third and most severe stage is proliferative retinopathy. When retinopathy becomes proliferative, there is a complete lack of oxygen to retina cells. The retina will try to compensate by producing vascular endothelial growth factor (VEGF), a signal protein that produces new blood vessels. These new blood vessels are abnormal, small, and weak. They can easily burst and cause bleeding in the eye. Patients in this stage often experience blind spots or floaters as symptoms. Hemorrhaging in the eye can cause sudden vision loss and requires immediate care.
The treatment for this stage is:
Laser photocoagulation — a procedure that uses a focused laser to stop blood vessels from bleeding and to stop new blood vessels from being formed
Anti-VEGF — a medication used to stop VEGF proteins from creating new blood vessels
This stage needs to be closely monitored by your eyecare provider!
Other Diabetic Eye Diseases
Diabetic Macular Edema
Even if you aren’t experiencing vision loss, it’s important for diabetic patients to go in for a yearly diabetic eye exam because diabetic macular edema (DME) can occur at any stage of diabetic retinopathy.
As the name suggests, this disease occurs in the macula, the center of the retina which processes sharp, color images. When DME occurs, blood vessels leak blood and fatty tissues into the macula, which then swells and causes the vision to blur. The vision lost from DME can be permanent.
Diabetes can also increase your risk of developing cataracts. Hyperglycemia can cause glucose to be converted to Sorbitol, a sugar alcohol. When Sorbitol accumulates, the lens of the eye becomes swollen and opaque and this leads to cataracts. To learn more about cataracts, see our previous article 5 Common Myths about Cataracts.
The risk of developing open-angle glaucoma is also increased with diabetes. This type of glaucoma occurs when the fluid in the eyes cannot drain and the resultant intraocular pressure damages the optic nerve and peripheral vision is diminished. To learn more about glaucoma, stay tuned for our upcoming articles Do I have Glaucoma? The Warning Signs and What is Intraocular Pressure? coming soon!
The most important take-away is to schedule your annual eye exam, especially if you are diabetic! Be sure to specifically request a diabetic eye exam if you are scheduling with a new eyecare provider.
Eye health education is part of our mission at Nanodropper. Learn how you can take back control of your eye health, one drop at a time.