A woman looks with a worried expression as her eyes inside her glasses look blurry.

Blurred Vision

Reviewed by: HU Medical Review Board | Last reviewed: March 2024 | Last updated: March 2024

Our bodies use insulin to maintain healthy blood sugar levels. Insulin is a hormone that helps sugar get into cells, where it is used to create energy. In type 2 diabetes, the body is resistant to insulin or does not make enough insulin. As a result, more sugar stays in the blood, increasing blood sugar levels.1

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High blood sugar can cause damage to different parts of the body, including the eyes. One of the symptoms of eye damage from diabetes is blurry vision. Maintaining healthy blood sugar levels can reduce your chances of getting blurry vision.1-3

Why does diabetes cause blurred vision?

High blood sugar levels can cause the lens inside the eye to swell and change shape. This can make it hard for 1 or both of your eyes to focus, which makes your vision blurry. As your blood sugar levels return to normal, the swelling should go away and your vision should become clear again.2,3

However, if your blood sugar levels stay high for a long time, your eyes can be severely damaged.2,3

For example, diabetic retinopathy affects the retina. The retina is found at the back of the eye. It is responsible for converting light that hits the eyes into signals for the brain. High blood sugar affects the blood vessels found near the retina. These blood vessels can leak, and abnormal blood vessels can start to grow. This damages the retina and can greatly reduce vision.2,3

High blood sugar increases the chances of developing other eye-related illnesses as well. These include:2,3

  • Diabetic macular edema – Swelling of the macula (the center of the retina). This can lead to loss of sharp vision needed for reading or driving.
  • Glaucoma – Damage to the optic nerve, which connects the eye to the brain. This can cause blurry vision and eventual loss of vision.
  • Cataracts – Cloudiness in the lenses of the eyes. This makes it harder for light to pass through the lens, leading to blurry vision.

In some cases, blurry vision can be due to low blood sugar instead. This happens because low blood sugar affects how the brain reads the signals from the eyes. Once your blood sugar levels return to normal, your vision should also return to normal.3

If your blood sugar levels change a lot, you might have blurry vision that comes and goes throughout the day. This might mean that you need to make changes to your treatment plan to maintain healthy blood sugar levels.3

How is blurred vision treated?

If you have not been diagnosed with diabetes, discuss your blurred vision symptoms with your doctor. Your doctor will measure your blood sugar levels to determine whether you may have diabetes.2,3

If you have diabetes, blurred vision is a sign that your blood sugar is out of control. You may need to adjust your diabetes treatment to maintain healthy blood sugar levels.2

Depending on the type and amount of damage to the eyes, other treatments also may be available. These treatments aim to slow down damage to the eyes and improve vision.4,5

How can I protect my vision if I have diabetes?

Maintaining healthy blood sugar levels can help protect your vision. Managing your blood pressure and cholesterol also can help lower your risk for vision problems.2,3

For people with type 2 diabetes, experts recommend having an eye exam once a year. For many eye-related diseases, you may not notice any symptoms until damage has been done. During an eye exam, the doctor will use different instruments and tests to check for damage inside your eyes. A yearly exam can help find any problems early.2-4

Have you experienced blurred vision?

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