Vision in people with diabetes can decline without warning. In its early stages, diabetic retinopathy usually causes no pain and no blurring, so many people only find out after significant damage has occurred. The good news: controlling blood sugar, blood pressure, and cholesterol, plus regular eye exams, can help prevent the disease or slow its progression.
How Does High Blood Sugar Damage the Eyes?
According to the U.S. Centers for Disease Control and Prevention (CDC) and the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK):
- Short term: vision can blur temporarily for days or weeks when a diabetes plan or medication changes; this usually resolves as blood glucose returns closer to normal (NIDDK).
- Long term: sustained high glucose damages the tiny blood vessels at the back of the eye. Vessels may leak fluid, weak new vessels may form and bleed, scar tissue may develop, and eye pressure may rise. NIDDK notes this process can begin as early as prediabetes.
4 Common Eye Conditions in Diabetes
| Condition | What it is | Key points (CDC, NIDDK) |
| Diabetic retinopathy | Retinal blood vessels weaken, bulge, or leak (early, nonproliferative stage); in the advanced (proliferative) stage, abnormal new vessels grow on the retina’s surface and can bleed | The most common cause of vision loss in people with diabetes; CDC calls it the leading cause of blindness among working-age adults in the U.S. |
| Diabetic macular edema | Swelling of the macula, the central retina used for reading, driving, and recognizing faces, from leaking fluid | Can destroy sharp central vision; CDC says about half of people with diabetic retinopathy develop macular edema |
| Cataracts | Clouding of the lens | Develop earlier and more often in diabetes; risk about twice that of people without diabetes (NIDDK) |
| Glaucoma | Optic nerve damage, usually from high eye pressure | Roughly double the risk of open-angle glaucoma; diabetes can also cause neovascular glaucoma (CDC, NIDDK) |
Symptoms: Often None Until Late
According to CDC and NIDDK, diabetic retinopathy often has no symptoms early on. Later, it can cause:
- Blurry or wavy vision, or fluctuating vision.
- Spots or dark shapes (floaters) and flashes of light.
- Trouble seeing colors.
- Dark or empty areas in your vision, or vision loss.
Glaucoma also often has no symptoms, and vision can be lost very gradually. So having no symptoms doesn’t mean your eyes are safe.
When to Seek Urgent Eye Care
NIDDK warns that sudden vision changes, a burst of new floaters or flashes, or a curtain-like shadow over your vision may signal a detached retina, which is a medical emergency. CDC likewise advises calling your eye doctor promptly about sudden changes such as blurring, spots, flashes, blind spots, distortion, or difficulty reading or doing detailed work. Don’t wait for your next routine appointment.
How Often Should You Have an Eye Exam?
The best way to catch problems early is a dilated eye exam, in which drops widen the pupils so the doctor can examine the back of the eye. According to CDC and NIDDK:
- Type 2 diabetes: get an exam right after diagnosis, then yearly.
- Type 1 diabetes: begin yearly exams within 5 years of diagnosis.
- Yearly is the minimum for most people; those with existing retinopathy may need more frequent checks.
- Pregnancy with type 1 or type 2 diabetes: an exam before pregnancy or in the first 3 months, with repeat exams possibly needed later in pregnancy and until the baby is 1 year old, since eye problems can develop quickly. Gestational diabetes usually doesn’t require an eye exam because it typically doesn’t cause eye disease (NIDDK).
Vision stays blurry for a few hours after dilation. Practical suggestion from this article: bring someone with you or plan your ride home.
Prevention and Slowing Progression
According to CDC and NIDDK:
- Manage the diabetes “ABCs”: A1c (blood sugar), blood pressure, and cholesterol within your doctor’s targets.
- Quit smoking.
- Stay physically active.
- Get regular eye exams as above. Starting early is best, but it’s never too late.
If Damage Has Already Occurred, Can It Be Treated?
NIDDK describes these treatments (decided by an eye specialist):
- Anti-VEGF injections (aflibercept, bevacizumab, ranibizumab): injected into the eye to block abnormal vessel growth and stop fluid leakage; they can stop further vision loss and sometimes improve vision. The eye is numbed first.
- Laser photocoagulation: seals leaky vessels or shrinks abnormal ones. Good at preventing further loss but less effective than anti-VEGF at restoring lost vision.
- Vitrectomy: surgery for severe bleeding or scar tissue pulling on the retina.
- Cataract surgery: replaces the cloudy lens with an artificial one; vision often improves, though results depend on any retinopathy or macular edema.
If vision loss can’t be corrected with glasses, medicine, or surgery, low vision and rehabilitation clinics can help people make the most of remaining sight (NIDDK).
The Bottom Line
Eyes are among the organs diabetes can damage without warning. The three most important moves are keeping blood sugar, blood pressure, and cholesterol in target, not smoking, and having a dilated eye exam at least yearly. And when vision changes suddenly, get checked right away rather than wait.
This article synthesizes and paraphrases the sources below and is for general educational purposes only; it does not replace professional medical advice. Exam schedules and treatment should be set by your eye doctor; the recommendations above come mainly from U.S. health agencies.
Sources referenced:
- CDC, Diabetes and Vision Loss (cdc.gov/diabetes/diabetes-complications/diabetes-and-vision-loss.html)
- NIDDK, Diabetic Eye Disease (niddk.nih.gov/health-information/diabetes/overview/preventing-problems/diabetic-eye-disease)