Why Blurry Vision Occurs in People With Diabetes

When people have diabetes, it means that their bodies do not make enough insulin or insulin can't be absorbed properly. This is known as high blood sugar, or hyperglycemia. People with diabetes can also experience low blood sugar, which is called hypoglycemia.

Along with blood sugar levels, diabetes can affect many organs and blood vessels in the body if it is not controlled. This includes the eyes. A common warning sign for diabetes is blurry vision. Other eye issues that diabetes can cause include swelling, weakened blood vessels, and damage to the retina.

If you notice a change in vision, contact a healthcare professional to find out the reason and to seek the proper treatment.

close-up of woman's eyes

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Hypoglycemia 

Hypoglycemia occurs when the body's blood sugar levels are too low. Typically, when blood sugar level falls below 70 milligrams per deciliter (mg/dL), hypoglycemia can occur. It is important to check with your healthcare provider to get your specific numbers so you can monitor accordingly.

Low blood sugar levels can have a dangerous outcome and lead to insulin shock, which can severely affect brain function.

Symptoms of hypoglycemia include:

  • Feeling shaky
  • Nervousness
  • Sweating
  • Confusion
  • A fast heartbeat
  • Headache
  • Irritation
  • Blurry vision

If a person experiences blurry vision as a hypoglycemic, vision regulates when the blood sugar levels are back to normal. Since blood sugar levels are known to fluctuate throughout the day, this inconsistency can also cause blurry vision.

Hyperglycemia

Hyperglycemia occurs either when the body does not produce insulin on its own or when a person needing insulin therapy has not given themselves enough insulin, depending on the type of diabetes.

If an individual has type 1 diabetes and becomes hyperglycemic, they have not given themselves enough insulin. If an individual has type 2 diabetes and experiences hyperglycemia, it means that their body doesn’t naturally produce enough insulin or doesn't use insulin properly.

Symptoms of hyperglycemia include:

High blood sugar levels can cause swelling of the eye’s lens. This happens because high blood sugar levels cause fluid to move in and out of parts of the eye. When the eye lens swells, the shape changes and this affects the eyesight.

Over time, the blood vessels in the eyes will weaken. Typically, if blurry vision is caused by hyperglycemia, clear vision will return when blood sugar levels normalize.

Causes and Complications 

Starting Insulin Treatment

For a person with diabetes, starting an insulin treatment plan may cause blurry vision. However, the body will eventually get used to treatment and blurry vision will stop. This initial blurry vision is normal and temporary.

It is important to work closely with your healthcare professional and let them know of any questions or concerns you may have or changes you are experiencing as your body and eyes adjust to the treatments.

Diabetic Retinopathy

Diabetic retinopathy is caused by high levels of sugar in the bloodstream. This condition is a serious complication that can lead to blindness as it can damage the area of the retina that is responsible for sending visual signals to the brain.

There are two types of diabetic retinopathy:

  • Nonproliferative diabetic retinopathy (NPDR): Also known as background retinopathy, NPDR occurs in the early stages of the disease. When the blood sugar level is elevated, it causes microaneurysms and damage to the walls of tiny retinal capillaries. Over time, the microaneurysms will bleed and rupture.
  • Proliferative diabetic retinopathy (PDR): This condition is known to be more severe. It can cause vision difficulties, blindness, and retinal scarring. With PDR, new and abnormal blood vessels start to grow in the retina. These new blood vessels are weak and break, bleeding into the retina and possibly other tissues of the eye.

Glaucoma 

Glaucoma damages the eye’s optic nerve. This most commonly happens when fluid builds up and increases pressure in the eye.

This condition usually occurs in people who are over 60 years old. If an individual is diabetic, they are twice as likely to develop glaucoma.

Neovascular glaucoma can occur in individuals with uncontrolled diabetes and is a condition in which new blood vessels grow on the iris of the eye. These new blood vessels can cause a closure of the flow of fluid, which raises pressure on the eyes. Treatment options are laser surgery or drainage implants.

Macular Edema

Macular edema is caused by the accumulation of fluid in the central portion of the eye, or the macula, and produces swelling. This area of the eye has cells that are responsible for the vision that helps with reading, driving, and detailed sight. It can become problematic when the macula begins to swell, causing damage to the cells.

Macular edema can be a result of advanced stages of diabetic retinopathy. Management of this condition is normally done with an injection of medication into the eye.

Prevention

It is important to maintain a healthy lifestyle and follow your doctor’s treatment plan regarding your diabetes. Two steps that can be taken to reduce or prevent blurry vision are keeping your blood sugar under control and keeping up with your yearly eye exams.

Other preventive measures include:

  • Maintaining a healthy diet that includes leafy greens, colorful vegetables, and fish high in omega-3 fatty acids.
  • Participating in regular exercise that is approved by your doctor
  • Maintaining a healthy blood pressure to reduce damage to the optic nerve

When to See a Doctor

It is important to keep up with yearly eye exams and to see a specialist when needed. With the progression of diabetes, the blood vessels can be permanently damaged. Blurriness is a strong indicator of an issue. Seeing a doctor regularly will help you call out any changes to your vision.

Other symptoms include the following:

  • Consistently red eyes
  • Problems with peripheral vision
  • Pressure in the eyes
  • Spots, floaters, or halos
  • Difficulty with night vision
  • Seeing double

Some individuals don’t have many symptoms at first, with the damage starting slowly. It is important to work closely with your healthcare professional to stick to your maintenance plan, going to the recommended appointments in order to prevent any additional issues and keep your condition under control.

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Article Sources
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  2. UCLA Health. For diabetics, blurry vision is cause for concern. Updated November 29, 2017.

  3. American Diabetes Association. Hypoglycemia (low blood glucose).

  4. Optometrist Network. Why does diabetes cause blurry vision? September 23, 2020.

  5. American Diabetes Association. Diabetic retinopathy and diabetic macular edema.

  6. Optometrist Network. Diabetic retinopathy. June 1, 2020.

  7. Glaucoma Research Foundation. Diabetes and your eyesight. Updated October 29, 2017.