Why Diabetes Can Change the Prescription for Your Glasses
When your glasses don't seem to improve your vision as well as they once did, diabetes could be to blame. High blood sugar or changes in blood vessels inside your eyes can cause blurry vision. Luckily, a visit to your optometrist can help you determine if you really need a new pair of glasses.

Blurry Vision Could Be Due to Temporary Changes in the Eye's Lens
The clear lens inside your eye focuses light on the retina. The retina changes light into electrical impulses, which it sends to the brain. Once the brain receives the impulses, it converts the impulses to images and adds them to your visual memory.
High blood sugar increases fluid levels inside the eye and changes the shape of the lens, which makes it work less effectively. As a result, your vision may look blurry. The change is only temporary, according to the National Institute of Diabetes and Digestive and Kidney Diseases. When your blood sugar returns to normal, your vision will probably be sharp again.

Diabetic Retinopathy or Macular Edema May Be Responsible for Vision Changes
Blurry vision can also be caused by diabetic retinopathy or macular edema. You may develop either of these conditions if your blood sugar remains high for a long time.
As of 2021, diabetic retinopathy affected more than 9 million people in the U.S. and was most common in people in the 65 - 79 age group, according to the Centers for Disease Control and Prevention. Diabetic retinopathy occurs when blood vessels in the retina swell and leak blood or fluid. New, abnormal, leaky vessels can also form.

The fluid or blood interferes with vision and can scar the retina, causing permanent vision loss. You can have diabetic retinopathy yet notice no changes in your vision in the early stages of the disease. Eventually, diabetic retinopathy may cause:

Blurry Vision That Comes and Goes
Trouble Focusing When Reading or Looking at Close Objects
Less Vibrant Colors
Dark Spots or Missing Areas of Your Vision
Poor Night Vision
Floaters (Wispy strings or spots that float your field of vision)

Diabetic macular edema damages the blood vessels in the macula, the middle part of the retina necessary for good color and central vision. Blood vessels that swell and leak blood or fluids also cause vision problems if you have macular edema. The condition also causes blurry vision, dull colors, and floaters.

Since the blood vessels in the middle of the retina are damaged, you may notice blank or blurry spots in the center part of your vision. This can make it difficult to read, recognize faces, or drive. If you have macular edema, you may notice that lines that should be straight instead look wavy.

Other Causes of Blurry Vision
High blood sugar levels also increase your risk for cataracts and glaucoma, two conditions that cause blurry vision. Cataracts happen when the clear lens inside your eye becomes cloudy. In a research study published in the Journal of Clinical Medicine in 2024, 32.9% of study participants with diabetes had cataracts. The researchers noted that the risk of developing cataracts varied depending on the patients' ages and the length of time they had diabetes.

Glaucoma happens when pressure inside your eye becomes too high and damages the optic nerve, the connection between the brain and the eyes. New blood vessels in the eye may block drainage channels in the eye, causing pressure to rise. Open-angle glaucoma, the most common type, doesn't usually cause noticeable changes in vision at first, although the optic nerve may still be damaged.

Do You Need New Glasses?
You may not need new glasses if blurriness is related to fluctuating blood sugar levels. Once you get blood sugar under control, your vision should improve. If you get new glasses when your vision isn't stable, you may need to update your prescription again in a few weeks.

If blurriness continues when your blood sugar level is normal, you may need a new prescription. Don't wait to call the optometrist's office if blurriness is severe or you have any of the symptoms of diabetic retinopathy or macular edema.
Wondering if the changes in your vision are related to diabetes? Contact our office to schedule an appointment with the eye doctor.

Sources:
Michigan Medicine: Diabetes and Your Eyes: 4 Things to Know, 12/2/2021
https://www.michiganmedicine.org/health-lab/diabetes-and-your-eyes-4-things-know
National Institute of Diabetes and Digestive and Kidney Diseases: Diabetic Eye Disease
https://www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/diabetic-eye-disease
MedlinePlus: Diabetic Eye Problems, 11/13/2024
https://medlineplus.gov/diabeticeyeproblems.html
National Eye Institute: Diabetic Retinopathy, 9/11/2025
https://www.nei.nih.gov/eye-health-information/eye-conditions-and-diseases/diabetic-retinopathy
Centers for Disease Control and Prevention: VEHSS Modeled Estimates: Prevalence of Diabetic Retinopathy, 5/15/2024
https://www.cdc.gov/vision-health-data/prevalence-estimates/dr-prevalence.html