To understand diabetic retinopathy, it helps to understand what's happening inside the eye at a basic level.

The retina is full of tiny blood vessels, some so small they're called capillaries, that deliver oxygen and nutrients to the retinal cells that make vision possible. When blood sugar stays elevated over time, it puts stress on those vessels in a way that gradually weakens them. They can start to swell, leak fluid, or even become blocked. When they're blocked, parts of the retina stop getting the oxygen they need.

In response to that oxygen shortage, the retina can send out signals that trigger the growth of new blood vessels. This sounds like a helpful response, but the new vessels that grow are actually fragile and abnormal. They can bleed easily, and the scar tissue that forms around them can pull on the retina in ways that cause serious problems.

A related condition called diabetic macular edema (DME) can develop at any stage of diabetic retinopathy. The macula is the small central area of the retina responsible for your sharpest vision, the kind you use to read, recognize faces, and see fine detail. When fluid leaks and builds up in or near the macula, it causes swelling that can blur or distort central vision.

Diabetic retinopathy is typically described in two major phases, and understanding them can help you make sense of what your eye care provider may tell you.

Nonproliferative diabetic retinopathy (NPDR) is the earlier stage. "Nonproliferative" means that abnormal new blood vessels haven't started growing yet. During this phase, the existing blood vessels in the retina are weakening, swelling, and beginning to leak. Tiny bleeds called dot hemorrhages or deposits called hard exudates may be visible on the retina during an eye exam. NPDR can range from mild to severe, depending on how widespread the changes are. Vision may still feel completely normal, or there may be some blurring if swelling is affecting the macula.

Proliferative diabetic retinopathy (PDR) is the advanced stage. "Proliferative" refers to the growth of those new, abnormal blood vessels described above. Because these vessels are fragile, they can bleed into the gel-like fluid that fills the inside of the eye, causing sudden floaters or vision changes. Scar tissue can also form and pull on the retina. This stage carries a significantly higher risk of serious vision loss than the earlier stage.

It's worth knowing that diabetic retinopathy doesn't always move steadily from one stage to the next. How quickly it progresses, or whether it progresses at all, depends largely on how well blood sugar and related risk factors are managed over time.

In the early stages of diabetic retinopathy, there often aren't any symptoms to notice. That's one of the most challenging aspects of this condition, because by the time something feels wrong, the disease may have already progressed significantly.

As diabetic retinopathy advances, symptoms can include:

• Blurry or hazy vision that comes and goes or becomes more consistent over time
• Difficulty reading or doing tasks that require sharp central vision
• Colors that look washed out or less vivid than they used to
• Floaters, which are spots, threads, or cobweb-like shapes that drift across your visual field
• Dark or empty areas in your vision, particularly in the center
• Sudden vision changes, including a dramatic increase in floaters or a significant drop in vision clarity

If you experience a sudden change in vision, a large number of new floaters, or a dark shadow or curtain appearing in your visual field, don't wait for a scheduled appointment. Contact an eye care provider promptly, as these can be signs of bleeding or retinal detachment that need timely attention.

Anyone with diabetes can develop diabetic retinopathy, but certain factors increase the likelihood and can influence how quickly it progresses.

• Duration of diabetes is the strongest risk factor. The longer someone has had diabetes, the higher the cumulative risk of developing retinopathy.
• Blood sugar control plays a major role. Chronically elevated blood sugar puts more sustained stress on retinal blood vessels than blood sugar that's kept closer to goal levels.
• High blood pressure adds additional stress to blood vessels throughout the body, including those in the retina.
• Abnormal cholesterol or lipid levels can also contribute to blood vessel damage and increase the likelihood of deposits forming in the retina.
• Kidney disease related to diabetes is associated with a higher risk of diabetic retinopathy, since both conditions involve damage to small blood vessels.
• Pregnancy in someone who already has diabetes can accelerate the onset or progression of retinopathy, which is why eye monitoring during and around pregnancy is especially important.
• Smoking is harmful to blood vessels throughout the body and adds to the cumulative risk for people with diabetes.

Understanding your personal risk profile is worth a conversation with both your eye care provider and your diabetes care team, since managing these factors can meaningfully affect your eye health over time.

Diabetic retinopathy is diagnosed through a comprehensive eye exam, and the most important part of that exam involves dilating your pupils. Dilation means using eye drops to temporarily widen the opening in the center of your eye, which allows the provider to see much further into the back of the eye and get a clearer view of the retina and its blood vessels.

A standard evaluation for diabetic retinopathy typically includes:

• Dilated fundus examination, in which the provider uses specialized lenses and lighting to carefully examine the retina, macula, and optic nerve for any signs of damage or abnormal vessels
• Visual acuity testing to measure how clearly you can see at various distances
• Optical coherence tomography (OCT), a non-invasive imaging scan that creates detailed cross-sectional images of the retina and can detect swelling in or near the macula that might not be visible otherwise
• Fundus photography, where photographs are taken of the back of the eye to document findings and track changes over time
• Fluorescein angiography, in some cases, where a dye is used to highlight the blood vessels in the retina and reveal leaking, blockages, or abnormal vessel growth more clearly

The exam findings are used to determine the stage of retinopathy and whether diabetic macular edema is present, which guides decisions about how frequently you need to be monitored.

Because diabetic retinopathy so often develops without symptoms, scheduled eye exams are the cornerstone of protecting your vision, not just exams when something feels wrong.

General guidance for when to start and how often to be screened includes:

• Type 1 diabetes: A comprehensive dilated eye exam is generally recommended within five years of diagnosis, and then on a regular schedule after that.
• Type 2 diabetes: A dilated eye exam is generally recommended at the time of diagnosis, since some people with type 2 diabetes already have retinopathy when they're first diagnosed.
• Ongoing monitoring: If exams show no retinopathy and blood sugar is well managed, your provider may recommend exams every one to two years. If retinopathy is present or progressing, more frequent monitoring is typically advised.
• Pregnancy: People with preexisting diabetes who become pregnant generally need eye exams early in the pregnancy and close follow-up throughout, since pregnancy can accelerate retinopathy.

Your individual schedule may be adjusted based on your exam findings, overall diabetes management, and other health factors. The key is to keep those appointments even when you feel fine, and your vision seems sharp.

While there's no way to guarantee that diabetic retinopathy won't develop, there are meaningful steps that can help reduce your risk or slow its progression. Most of them center on keeping the conditions that damage blood vessels as controlled as possible.

• Manage your blood sugar as consistently as you can. The relationship between blood sugar control and retinopathy risk is one of the most well-established in diabetes care.
• Keep blood pressure in a healthy range. High blood pressure adds stress to already vulnerable retinal vessels.
• Address cholesterol and lipid levels through diet, lifestyle, and any guidance from your healthcare provider.
• Don't smoke. Smoking affects blood vessels throughout the body, including in the eyes.
• Stay current on eye exams, even when your vision feels fine. This is one of the most important things you can do.
• Communicate across your care team. Your eye care provider and your diabetes care provider both play important roles, and keeping them informed of each other's findings helps ensure nothing falls through the cracks.

Living with diabetes involves a lot of moving parts, and eye health is one of the ones that's easy to put on the back burner, especially when vision feels normal. But the window for protecting your eyes is most open before visible damage occurs, and regular monitoring is what keeps that window available to you.