If you are diabetic, you have likely been told by your primary care doctor that you need to see an eye doctor yearly. But why is this so important?
Diabetes is a systemic health problem, meaning it affects the entire body—including the eyes!
What is Diabetes?
Diabetes is a problem in which the body does not correctly process sugar, leading to an accumulation of too much sugar in the blood.
There are several different types of diabetes with the most common types being Type 1 and Type 2.
Type 1 Diabetes is also known as Insulin-Dependent Diabetes and Juvenile Diabetes.
Type 1 Diabetes is an auto-immune disease in which the body attacks its own pancreas—resulting in destruction of insulin-producing cells called the islets of Langerhans. When this happens, too little insulin is produced by the body.
Insulin is needed to regulate the amount of sugar (glucose) in the blood. When levels get too high, insulin comes in and turns the sugar into energy or stores it for later use.
When there is not enough insulin circulating in the blood stream, excess sugar builds up in the blood vessels and causes damage to the vessels.
Type 2 Diabetes also results in too much sugar being in the blood, but it has a different underlying process.
Type 2 diabetics still have the ability to produce insulin, their bodies just become resistant to it (i.e. insulin tells the body to store the sugar away, but it does not listen) or cannot make enough insulin to keep up with the amount of sugar being consumed.
In other words, there is some insulin floating around the blood stream, but it is not doing its job well enough anymore, leading to accumulation of excess sugar in the blood.
Overview of Diabetic Retinopathy
The main part of the eye responsible for detecting light and transmitting it to the brain is call the retina (the backmost structure of the eye).
Like all other body parts, the retina has a blood supply to keep it strong and healthy. However, the blood vessels in the retina are unique because they contain tight junctions—special connector cells that inhibit the leakage of blood, proteins, and fluids out of the vasculature.
Think about tight junctions almost like a waterproof insulator surrounding the blood vessels of the retina. Nothing can pass through these cells unless they say so.
Tight junctions are very important in the retina as blood is toxic to the retinal cells—too much leakage from blood vessels into the retina can lead to permanent damage and potential irreversible vision loss.
Unfortunately for diabetics with uncontrolled blood sugar, when blood sugar levels get too high and sugars accumulate within the blood vessels, it causes structural damage to the vessels and fluids can begin to leak out of the vessels and into the retina.
These structural changes leading to leakage of fluids and proteins into the retina is called retinopathy.
Diabetic retinopathy is currently the leading cause of preventable blindness in the United States.
Diabetic retinopathy is the reason primary care doctors encourage their diabetic patients to see their eye doctors yearly, as the sooner retinopathy is detected and treatment can be initiated—the better the overall prognosis.
Diabetic retinopathy is typically not painful, therefore many individuals will not realize they are having vascular changes within the eye. This why annual dilated eye exams that allow your eye doctor to easily assess the health of the retina is so important.
Diabetic retinopathy occurs in both type 1 and type 2 diabetics.
The #1 risk factor for development of diabetic retinopathy is how long an individual has had diabetes. It typically starts in the mild stages and progresses with time.
However, in patients with uncontrolled blood sugar, signs of diabetic retinopathy can occur significantly earlier and be more severe.
Diabetic retinopathy is categorized by how much damage is occurring to the retina. It can be non-proliferative or proliferative.
Non-Proliferative Diabetic Retinopathy
“Proliferative” means the growth of new blood vessels. We do not want this in the eye as these new blood vessels can interrupt the structures of the retina and lead to loss of vision.
Non-proliferative retinopathy occurs when there are retinal changes without new blood vessel growth.
Non-proliferative retinopathy can be categorized as mild, moderate, or severe.
Staging of non-proliferative retinopathy depends on how extensive the retinal changes are.
Eye doctors divide the eye into 4 quadrants with the center of the cross being located at the optic nerve head. The more quadrants involved, the higher the staging of the disease.
Findings with non-proliferative diabetic retinopathy include microaneurysms (small leakage of blood vessels), dot-blot hemes (pinpoint spots of bleeding), exudates (build–up of proteins and lipids that have leaked from the vessels), cotton wool spots (areas of ischemia, or damage to retinal cells resulting in the appearance of a white fluffy focal area near the retinal vasculature) and enlargement of sections of vessels (venous beading).
Proliferative Diabetic Retinopathy
Proliferative diabetic retinopathy is significantly more serious in terms of retinal damage.
Fortunately, with regular eye exams and proper treatment, only 5-10% of type 2 diabetics reach this stage.
On the other hand, unfortunately, 60% of type 1 diabetics will have progression to this stage after 30 or more years of the disease.
As briefly mentioned earlier, proliferative retinopathy mean proliferation, or growth, of new blood vessels. This is also referred to as neovascularization.
This process occurs when death (ischemia) of the retina (from a combination of all the microaneurysms, hemes, cotton wool spots, venous beading, etc.) becomes so great that the retina releases a signaling factor called VEGF.
VEGF signals the body to start growing new blood vessels anywhere and everywhere possible to try and get proper nutrition to the area that is dying.
Think about VEGF being like an emergency last ditch effort by the body to try and repair the damage. In other parts of the body, these new blood vessels can be beneficial. However, in the eye, these vessels cause more harm than good.
New weak and leaky blood vessels begin to grow from the retina and into the gel-like substance of the eye called the vitreous.
The vitreous has the consistency of Jell-O and makes up over two-thirds of the internal space of the eye. It provides structural support and nutrition to surrounding structures.
The vitreous is also flexible and moves with eye movement. Movement and blood vessels is not a good combination.
When the vitreous moves, it can tug on these new leaky blood vessels, causing them to tear and bleed. When blood enters the vitreous, it can cause vision to look hazy, and hence drastically decrease visual acuity.
In some cases, however, the blood vessels do not tear but instead are yanked around.
Remember that these new blood vessels are growing out of the retina and into the vitreous. When they are yanked around, they can tug and pull on the retina causing retinal holes, tears, and even detachments.
These problems are very serious and if not treated immediately, can result in permanent loss of vision.
Like non-proliferative retinopathy, proliferative retinopathy is also broken down into sub-categories based upon severity and progression of disease.
Proliferative diabetic retinopathy can be categorized into mild, high risk, and advanced proliferative diabetic retinopathy. Staging depends on the location of the neovascularization and the size of the neovascularization.
I am Diabetic, What Should I Do to Prevent These Changes?
The best thing you can do to prevent diabetic retinopathy is to get yearly eye exams to monitor for changes and to do your best to keep your blood sugar levels under control.
We suggest aiming for an HbA1c below 7.0% and that you regularly check your blood glucose levels to ensure your sugar levels are staying within your set goals established by your primary care doctor.
While there are treatments including shots and laser surgeries to help treat severe forms of diabetic retinopathy, it is best to try and prevent these changes from occurring at all as it can be hard to predict what cases will result in permanent vision loss.
Since your primary care doctor is the one routinely following your care plan specific for diabetes, we recommended regular exams with your primary care doctor as well—at least once a year!
Your primary care doctor and eye doctor will work together as a team to ensure you are getting the best care to manage your diabetes.
If you notice vision fluctuations (i.e. blurry one day and fine the next), a “curtain or veil” over vision, or a sudden increase in flashes or floaters, call your eye doctor immediately as these can be signs of ocular pathology. The sooner you get in to see your doctor and the sooner treatment can be initiated, the better.
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