Blurry vision makes it hard to see fine details. Things lack sharpness like the out-of-focus parts of a photograph. One reason for blurry vision can be diabetes.

Both short- and long-term complications can affect the eyes and eyesight of people with diabetes.

The blurriness can be subtle or obvious, change through the day, and come on slowly or quickly, depending on the cause.

In this article, we explain how diabetes affects the eyes and how to protect the eyes. It also looks at some other possible causes of blurry vision.

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Short-term blurriness can happen because of high or low blood sugar.

High blood sugar (hyperglycemia)

In a person with diabetes, fluid can move into and out of the eye due to high blood sugar levels, also known as hyperglycemia. This can cause the lens of the eye to swell.

As the shape changes, blurriness results because the lens is the part that focuses light onto the back of the eye. This is a short-term issue that tends to resolve when blood sugar levels fall.

Low blood sugar (hypoglycemia)

People who use insulin may experience hypoglycemia, when blood sugar levels fall too low.

This can lead to:

When blood sugar levels rise, these changes usually resolve.

Long-term eye complications that result from diabetes tend to be progressive. This means they usually worsen over time.

Here are some long-term problems that can occur.

Diabetic retinopathy

Diabetic retinopathy affects a part of the eye known as the retina. It can lead to vision loss in some cases.

In Western countries, diabetic retinopathy is the most common reason for vision loss. It is the main condition that specifically affects people with diabetes.

It happens when high blood sugar levels affect tiny blood vessels in the eye.

There are two stages.

The early stage is nonproliferative diabetic retinopathy (NPDR), also known as background retinopathy. People may not notice symptoms at this stage.

In time, some people develop proliferative diabetic retinopathy (PDR). This is an advanced stage that can severely impact vision.

Diabetic retinopathy does not always progress to PDR, but statistics suggest that when NPDR becomes very severe, 75% of cases will progress to PDR within a year.

Nonproliferative retinopathy

NPDR can be mild, moderate, severe, or very severe.

A person with mild NPDR may not notice symptoms, but the following changes can start to occur in the blood vessels:

  • weakening
  • blockages
  • bulging
  • leakage of fluid

There may be swelling in the central part of the retina. This is known as macula edema. It can affect vision as it affects the central part in the back of the eye, which allows people to see fine details.

NPDR can be mild, moderate, or severe, depending on how severely it affects the blood vessels.

Proliferative diabetic retinopathy

In PDR, blood vessels cannot deliver blood to the retina effectively because they are blocked. New vessels start to grow to compensate for this, but they do not deliver blood to the eye in a helpful way. They can make symptoms worse.

There may be:

  • bleeding from the blood vessels
  • floating spots or lines in the field of vision
  • difficulty seeing faraway objects
  • scarring on the eye’s surface

It does not cause red eyes as the bleeding is at the back of the eyes.

The symptoms may come and go.

New vessels can also start forming in the iris, the part that gives people their eye color. This affects the balance of fluid inside the eye.

People with diabetic retinopathy have a higher chance of developing:

  • diabetic macular edema
  • neovascular glaucoma
  • retinal detachment

Other conditions

Other causes of vision loss can occur alongside diabetes, especially as people get older.

They include:

  • cataracts, where the surface of the eye becomes cloudy
  • glaucoma, when a buildup of pressure in the eye affects the main nerve going from the eye to the brain
  • damage to the eye’s surface
  • diabetic papillopathy, or swelling in one or both optic nerve discs and fluid accumulation, due to leakage from blood vessels
  • macular degeneration
  • retinal vascular occlusion
  • acute ischemic optic neuropathy

Optic neuritis is a rare condition. In some cases, it may have links with type 1 diabetes, according to a small case study published in 2018.

Some people notice vision changes when they start using insulin to treat high glucose levels.

An older study from 2010 looked at how starting insulin treatment affected the vision of 26 people with diabetes. Nine people reported an increase in blurriness after 3 days, but their vision returned to its original state after 10 days.

Blurry vision can result from both short- and long-term complications of diabetes.

Short-term blurriness due to high or low blood sugar levels will usually resolve when blood sugar levels return to 70–130 milligrams per deciliter (mg/dL).

Conditions that result from persistently high blood sugar levels, such as diabetic retinopathy, are progressive diseases and tend to worsen with time.

Other long-term complications that are more common in people with diabetes are:

  • macular degeneration
  • glaucoma
  • cataracts

It may not be possible to reverse the damage resulting from these conditions, but managing glucose levels and following a treatment plan can help slow their progression.

There are many possible causes of blurry vision, but it can be an early sign of diabetes.

A person should see an eye doctor if:

  • they have diabetes and have not had a vision test within the past year
  • they notice unexplained vision changes
  • they have a diagnosis of diabetes and notice vision changes
  • vision changes happen suddenly or get worse

Eye problems can stem from new cases of diabetes or a complication of an existing condition.

Why is eye screening important for people with diabetes?

Regular diabetes eye checks

People with diabetes need regular, specialist eye checks with an optometrist or an eye doctor (ophthalmologist). This will involve a dilated eye exam.

First, the specialist will administer eye drops to enlarge the pupils.

Then, they will examine the retina, at the back of the eye, for any changes or unusual features. They will look for signs of diabetic retinopathy.

A doctor may recommend an eye exam once a year or more, depending on the person’s current eye health.

People need more regular checks during pregnancy as retinopathy can worsen during this time.

What happens during a diabetes eye exam?

For people with diabetes, regular diabetes eye exams can detect problems in the early stages.

If early signs of eye problems are present, a doctor will likely recommend:

  • a treatment plan to help manage glucose levels
  • managing high blood pressure, which can also affect eye health
  • more regular eye tests and monitoring

These measures can slow or prevent further changes for some time.

Medical options

A doctor may recommend medical treatment if symptoms progress.

Diabetic retinopathy

If diabetic retinopathy becomes severe, an eye doctor may recommend:

  • Anti-VEGF injections: A doctor injects an anti-VEGF drug, such as Eylea (aflibercept), into the eye to stop new blood vessels from forming. VEGF, refers to vascular endothelial growth factor, a protein that stimulates blood vessel growth.
  • Steroid injections: The doctor may recommend these if anti-VEGF injections do not help.
  • Laser surgery: Laser treatment on the back of the eye can reduce swelling at the center of the retina. It can also shrink or prevent unusual blood vessel growth and prevent bleeds.
  • Microsurgery: A surgeon removes some of the jelly-like substance that builds up behind the lens through a small hole in the eye. A local anesthetic prevents pain during the procedure.

What can you expect during anti-VEGF injections?

Other conditions

Options for some other conditions include:

Cause of vision problemsTreatment
CataractsChanging glasses or using brighter lights may help. Surgery is a safe option if these are not effective.
GlaucomaOptions include prescription eye drops, laser treatment to drain fluid, and surgery to enable fluid to drain from the eye.
Macular degeneration (MD)Options include anti-VEGF injections and photodynamic therapy for wet MD, but there is no treatment for the more severe dry form.
Retinal vascular occlusionDepending on the cause and whether it affects the veins or arteries, this may involve medications (such as anti-VEGF), laser treatment, and surgery.
Acute ischemic optic neuropathyDepending on the type, a doctor may prescribe corticosteroids or suggest surgery to the optic nerve.

In each case, managing glucose levels can help prevent further deterioration and may prevent damage to the other eye, if the condition has not yet affected it.

People with eye problems related to diabetes can start taking preventive measures to protect their vision.

Tips include:

  • managing blood sugar levels to reduce the risk of diabetic retinopathy or stop it from getting worse
  • following the treatment plan a person agrees with a doctor, including specific dietary, exercise, and drug recommendations
  • managing high blood pressure, or hypertension, as this can contribute to eye problems
  • attending regular eye checks and seeking help if changes arise or complications occur

If retinopathy or other causes of eye problems progress to a later stage, a person may need specific eye treatments.

What are some natural remedies for blurry vision?

Diabetes is just one cause of blurriness, but there are many other causes.

Vision changes affect most people with age. Often, a new prescription for glasses or lenses will solve the problem.

Here are some other causes:

Dry eyes and screen use

Dry eyes are a common cause of blurriness. It can indicate a condition that needs attention — including diabetes — or may result from lifestyle habits.

One common reason is that people blink less when they look at a screen.

To prevent dry eyes, a person can try the following:

  • changing the lighting
  • blinking more
  • taking breaks away from the screen

The American Optometric Association recommends following the 20-20-20 rule to reduce the risk of eye discomfort when using a screen: Take a 20-second break every 20 minutes to look at something 20 feet away.

It is important to have an eyesight check from an optometrist, too.

Get some tips on preventing eyestrain while using a screen here.

Blurring after exercise or a hot bath

Sometimes blurred vision can occur after exercising or after a hot bath because of a condition known as Uhthoff’s phenomenon. This can affect people with neurological conditions such as multiple sclerosis.

Other symptoms include blurred or double vision.

Other causes

Other possible causes of blurry vision include:

What else can cause sudden blurry vision?

What does diabetes blurred vision look like?

It will depend on the cause. Overall, there may be a lack of sharpness and difficulty seeing fine details. People with diabetic retinopathy may also notice an increase in floaters, strings, and spots in the field of vision.

What level of blood sugar causes blurry vision?

Low blood sugar can affect vision if it falls below 70 mg/dL. If high blood sugar is the cause, vision should become clear again when glucose levels return to 70–130 mg/dL or below 180 mg/dL 1–2 hours after eating.

How do you know if diabetes is causing blurry vision?

If blurry vision happens suddenly, a glucose test may show that blood sugar levels are too high or too low. For longer-term conditions, such as diabetic retinopathy, an eye test can show if any vision changes are likely related to diabetes.

Blurry vision can be a complication of diabetes. Causes include diabetic retinopathy, cataracts, glaucoma, and high or low blood sugar. However, many of these may also occur in people without diabetes, especially as they get older.

Managing blood sugar levels and having regular eye tests can help prevent vision problems. Regular checks may also detect problems at an early stage when they are easier to treat.

For people with diabetes, it is a good idea to have regular eye checks with an eye specialist. Anyone with diabetes who has concerns about eye or vision symptoms should also seek medical advice.