A person with blurry vision is unable 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-term and long-term complications can affect the eyes and eyesight of someone with diabetes.

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

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Blurry vision can develop as a complication of diabetes.

Diabetes can have long-term or short-term effects on the eyes.

Long-term uncontrolled diabetes can lead to high blood sugar levels that damage small blood vessels over time. This damage can lead to problems with a part of the eye called the retina. This can create blurred vision.

Short-term blurriness happens for a different reason. In a person with diabetes, fluid can move into and out of the eye due to high blood sugar levels. 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 short-term issue tends to resolve when blood sugar levels fall.

Diabetes can also cause short-term blurriness if blood sugar levels fall too low. Low blood sugar is hypoglycemia.

Diabetes treatment and blurriness

For people who take medication to increase insulin in the body, changing the timing of food or a change in activity levels can result in low blood sugar levels.

Blurriness from low blood sugar does not result from changes in the eye. Instead, it is due to the way hypoglycemia affects the brain.

Vision that changes in this way will return to normal after glucose levels return to normal.

Is blurry vision with diabetes temporary?

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

Long-term eye problems stem from blood vessel damage in the retina of one or both eyes due to high blood sugar levels over the course of many years. These complications are not temporary, but treatment can slow their progression.

Short-term blurriness, due to high or low blood sugar levels, is temporary and will resolve when blood sugar levels return to normal.

A range of medical conditions can cause blurry vision, and diabetes is just one.

Most people who start to have blurry vision simply need eyesight correction with the help of an optometrist.

However, anyone who develops blurry vision—whether or not they have diabetes—should see a doctor, especially if:

  • a problem appears suddenly
  • the problem gets worse

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

Anyone who already has a diabetes diagnosis should go for a routine eye examination at least once a year. Regular tests can detect any problems while they are still minor.

Regular diabetes eye checks

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Regular eye checks are important for people with diabetes. These should be with an eye specialist rather than an optician.

A regular doctor or optician does not carry out the annual eye check for people with diabetes.

Instead, optometrist or an eye doctor—called an ophthalmologist—performs this specialist examination.

An eye doctor can then treat any problems that they find. Only ophthalmologists can treat a disease of the retina.

The specialist looks at the back of the eye—the retina—after making the pupil bigger with a drug delivered in eyedrops.

This is the dilated eye exam, and it detects the signs of diabetic retinopathy, a disease of the retina that results from diabetes.

If a person already has diabetic eye problems, the person will need multiple follow-up checks every year.

During pregnancy, a person should have more regular checks.

Eye complications due to diabetes are progressive. This means they are likely to get worse over time.

At first, symptoms are minor, and only a specialist eye examination can detect them. Later, eye or visual symptoms appear.

Progression of diabetic retinopathy

Retinopathy can worsen over time. Broadly, there are two stages.

Non-proliferative diabetic retinopathy (NPDR)

Also known as background retinopathy, this is the early stage, with mild or no symptoms.

At this stage, the retina's tiny blood vessels may become weak and blocked. There may be bulges in them, or fluid can leak out. This can cause swelling in the central part of the retina.

NPDR can be mild, moderate, or severe, depending on how serious the blood vessel problem is.

Swelling in the retina—or macula edema—can cause vision problems. This is because it is the central part in the back of the eye that allows people to see fine details clearly.

Proliferative diabetic retinopathy (PDR)

This is an advanced stage of eye complications. Blood vessels cannot deliver blood to the retina effectively, because they have closed up. New vessels start to grow to compensate for this. This stage only develops in some people with diabetes. It takes several years to develop.

The growth of new blood vessels does not provide normal blood flow to the retina, however, and it can lead to scarring and wrinkling. In severe cases, it can distort a person's vision. The retina can even become detached, causing a loss of vision.

The fragile new vessels can also bleed out. Symptoms include floating spots in the vision. If a bleed from the retina into the central fluid of the eye is big, a person can sometimes lose sight in that eye. After this, they will only be able to tell light from dark.

Eventually, 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.

Glaucoma

Glaucoma is another problem that can develop over time. This is a buildup of pressure in the eye that can affect the main nerve going from the eye to the brain.

For people with diabetes, regular eye checks can find problems in the earliest stages.

A positive outcome is when diabetes is well-controlled, and tests cannot detect changes to the back of the eye for a number of years.

When a doctor finds signs of retinopathy at its earliest stages, they can suggest ways to manage the problem.

These include monitoring and controlling those things that can affect eye health, such as high blood sugar level and high blood pressure.

Lifestyle measures

A person with a diagnosis of eye problems related to diabetes should start to take preventive measures to protect their vision.

Retinopathy is a progressive condition that gets worse if blood sugar levels remain too high, but managing blood sugar levels can help to reduce the risk.

Keeping blood sugar levels under control can prevent new problems from appearing and slow down any retinopathy that has already started.

The same diet, lifestyle measures, and medical treatment that people use for diabetes can also treat and prevent eye problems.

Good blood sugar control also helps to keep high blood pressure, or hypertension, under control. This is another risk factor for eye problems.

Regular checks and strict diabetes management are the best way to prevent eye problems and to manage complications once they occur.

However, if retinopathy progresses to a later stage, a person may need specific eye treatments.

Treatment options

If retinopathy becomes severe, an eye doctor may recommend:

Steroid treatment: The doctor may prescribe eye drops that contain steroids.

Injections in the eye: A doctor may use a very fine needle to inject a drug, known as anti-VEGF, into the eye. This aims to stop new blood vessels from forming in the eye.

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 abnormal blood vessel growth and prevent bleeds.

Microsurgery: A surgeon will make a small cut in the eye to remove some of the jelly-like substance that has built up behind the lens. They will use a local anesthetic, so the person will not feel any pain during the procedure.

Diabetes is just one cause of blurriness. Other causes include a deterioration of eyesight. This can happen at any time, but especially as people get older.

The person may need new glasses or a change of lens prescription.

Dry eyes and screen use

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Screen use can lead to dry eyes and blurry vision.

Dry eyes are a common cause of blurriness. One cause of dry eyes is when blinking is reduced over long periods of looking at a screen. Computer workers may notice blurred vision due to dry eyes.

To prevent dry eyes, try the following:

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

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

Other medical causes

Medical causes of blurred vision include cataracts and glaucoma. Both are more likely to develop in people with diabetes.

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 optic neuritis.

Other symptoms of this condition include:

  • dim vision
  • dulled or fading perception of color
  • pain behind the eye when moving the eyes

Anyone who experiences these symptoms should see a doctor.

Other possible reasons include low blood sugar, low blood pressure, running in the wind or cold, or the effect of sun or sunscreen.

Optic neuritis is a rare condition that may, in some cases, have links with type 1 diabetes, according to research published in 2018. The investigators were reporting on a small case study.

There are many reasons for blurry vision, aside from diabetes, cataracts, and glaucoma. Anyone with eye or vision symptoms should consult a doctor.