Diabetes and Your Eyes: What Every Diabetic Should Know

2024-07-01

If you have diabetes, you have probably heard that you should get your eyes checked regularly. But the urgency of that advice often gets lost between all the other things you are managing: blood sugar, medication, diet, exercise, foot care. Your eyes can feel like one more item on an already long list.

Here is why they need to be near the top: diabetic retinopathy is the leading cause of new blindness in working-age Canadians. And the cruelest part is that it causes no symptoms until significant damage has already occurred. By the time you notice something wrong with your vision, the disease has often been progressing for years.

The good news is that early detection and treatment can prevent vision loss in the vast majority of cases. This is not one of those conditions where the news is all bad. It is one where catching it early makes an enormous difference.

What Diabetes Does to Your Eyes

High blood sugar damages small blood vessels throughout your body. The retina, the light-sensitive tissue lining the back of your eye, has an extremely dense network of tiny blood vessels. These are among the first to be affected.

Over time, elevated blood sugar weakens the walls of these retinal blood vessels. They begin to leak fluid, swell, and eventually close off. As more vessels close, the retina starts losing its blood supply. In response, the eye grows new blood vessels to compensate, but these new vessels are fragile and abnormal. They leak easily, and they can bleed into the eye or pull on the retina, potentially causing detachment.

This process is called diabetic retinopathy, and it progresses through distinct stages.

The Four Stages of Diabetic Retinopathy

Stage 1: Mild Non-Proliferative

Small balloon-like swellings (microaneurysms) appear in the retinal blood vessels. At this stage, there are typically no vision symptoms at all. Your optometrist can see these during a dilated eye exam, but you would never know they were there on your own.

Stage 2: Moderate Non-Proliferative

More blood vessels become affected. Some begin to swell and lose their ability to transport blood normally. The retina is starting to receive less nourishment, but vision is usually still unaffected.

Stage 3: Severe Non-Proliferative

Many blood vessels are now blocked, depriving significant areas of the retina of their blood supply. The retina sends chemical signals requesting new blood vessel growth. Vision may still be normal at this point, which is what makes this disease so insidious.

Stage 4: Proliferative Diabetic Retinopathy

New blood vessels grow along the retina and into the vitreous (the gel that fills the eye). These new vessels are fragile and can rupture, causing sudden bleeding inside the eye (vitreous hemorrhage). This can cause sudden loss of vision. Scar tissue can also form and pull on the retina, potentially causing retinal detachment. This stage requires urgent treatment.

Diabetic Macular Edema: The Other Threat

Separate from the stages above, fluid can leak from damaged blood vessels into the macula, the central part of the retina responsible for sharp, detailed vision. This is called diabetic macular edema (DME), and it can occur at any stage of retinopathy. DME is the most common cause of vision loss in diabetic patients, causing blurred central vision that affects reading, driving, and recognizing faces.

Why Annual Dilated Exams Are Non-Negotiable

A regular eye exam where you read letters on a chart will not detect diabetic retinopathy. Your optometrist needs to look at the retina directly, which requires dilating your pupils with eye drops. This gives them a wide view of the blood vessels, the optic nerve, and the macula.

Dilation is mildly inconvenient. Your pupils stay large for 4 to 6 hours, making things blurry up close and sensitive to light. Bring sunglasses. Consider having someone drive you. But do not skip the exam because of it.

Many clinics, including ours, also use retinal imaging technology that can photograph the back of your eye in high resolution. This creates a baseline record that can be compared year to year to detect subtle changes. Some changes are so early they would be difficult to catch without side-by-side photo comparison.

Here is a number that should motivate you: early detection and treatment of diabetic retinopathy prevents severe vision loss in up to 95% of cases. Ninety-five percent. But that only works if you show up for the exam before symptoms start.

Blood Sugar Fluctuations and Vision

If you have diabetes, you may have noticed that your vision fluctuates from day to day or even hour to hour. This is real, not imagined, and it is caused by blood sugar levels affecting the lens inside your eye.

When blood sugar is high, the lens absorbs extra glucose and swells slightly, changing its focusing power. When blood sugar drops, the lens returns to its normal shape. This is why diabetic patients sometimes report that their glasses seem to work some days and not others, or that their vision got temporarily worse after starting a new medication.

This is also why we ask diabetic patients to have their blood sugar well-controlled and stable for at least 2 to 3 weeks before we prescribe new glasses. A prescription measured during a blood sugar spike will be inaccurate once levels stabilize.

What Treatment Looks Like

If retinopathy is detected early (stages 1 or 2), the primary treatment is better blood sugar control, blood pressure management, and regular monitoring. No eye procedures are needed at this point.

For more advanced retinopathy or macular edema, treatment options include:

Anti-VEGF injections: Medication injected directly into the eye that stops abnormal blood vessel growth and reduces fluid leakage. This sounds alarming, but the injection is quick and typically painless thanks to numbing drops. Many patients need a series of injections over months or years.
Laser treatment (photocoagulation): Targeted laser burns seal leaking blood vessels or reduce abnormal vessel growth. This has been used for decades and remains effective.
Vitrectomy: Surgery to remove blood and scar tissue from the vitreous. Reserved for advanced cases with significant bleeding or retinal detachment.

Alberta Coverage for Diabetic Eye Exams

Alberta Health Care Insurance Plan (AHCIP) covers annual comprehensive eye exams for all patients with diabetes, regardless of age. You do not need to pay out of pocket. This coverage exists because the government recognizes that catching diabetic eye disease early saves enormous treatment costs down the line, not to mention saving sight.

If you have diabetes and have not had a dilated eye exam in the past year, you are overdue. Call and book one. It is covered.

What You Can Do Right Now

Get your annual dilated eye exam. This is the single most important thing.
Manage your blood sugar. Every point you can lower your HbA1c reduces your retinopathy risk. Good glucose control is the most powerful protection your eyes have.
Control blood pressure. High blood pressure compounds the damage diabetes does to retinal blood vessels.
Do not smoke. Smoking damages blood vessels everywhere, including your retina, and significantly accelerates diabetic eye disease.
Tell your optometrist you have diabetes at every visit, even if you think they already know. It changes the exam protocol.

The Bottom Line

Diabetic retinopathy is a serious condition, but it is also one of the most preventable causes of blindness we know of. The treatment works, especially when started early. But early means before you have symptoms, which means you need those annual exams even when your vision feels perfectly fine.

Your eyes are not going to warn you that something is wrong. That is your optometrist's job, but only if you show up.