It is similar to seeing things as if they are in the out-of-focus parts of a photograph.
The blurriness can be subtle or obvious, can change through the day, and can come on slowly or quickly. It depends on the cause.
Diabetes can cause blurry vision for a variety of reasons. Both short-term and long-term complications can affect the vision of someone with diabetes.
How diabetes affects the eyes
There are many reasons why diabetes might cause blurry vision.
Long-term uncontrolled diabetes can lead to high blood sugar levels that cause damage to small blood vessels over time.
This damage can lead to problems with part of the eye called the retina which can create blurred vision.
Short-term blurriness in people with diabetes is due to a different cause.
Fluid shifts into and out of the eye due to high blood sugar levels, causing the lens of the eye to swell.
This change in its shape causes blurriness as the lens is the part that focuses light onto the back of the eye. This short-term issue will resolve once blood sugar levels are lowered.
Can diabetes treatment cause blurriness?
Diabetes can also cause short-term blurriness if blood sugar levels fall too low (hypoglycemia). This can happen due to the timing of food or a change in activity levels in people who take medication that increases insulin in the body.
Rather than being caused by changes in the eye, blurriness from low blood sugars is caused by the effects of hypoglycemia on the brain. Vision affected in this way will return to normal after glucose levels return to normal.
Is blurry vision with diabetes temporary?
As stated above, blurry vision can be caused by both short-term and long-term complications of diabetes.
Long-term eye problems are related to 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, although their progression can be slowed down.
Short-term blurriness due to high or low blood sugar levels is temporary and will resolve when blood sugar levels return to normal.
When should I see a doctor?
A range of medical conditions can cause blurry vision, and diabetes is just one.
Most people who begin to see things blurrily turn out needing eyesight correction with the help of an optometrist. However, anyone who develops blurry vision should see a doctor - especially if the problem has appeared suddenly.
Eye problems can be related to new cases of diabetes or a complication of an existing condition.
Whether diabetes has yet to be diagnosed or is already under medical care, it is important for a person to get checked when blurry vision develops.
Anyone who already has a diabetes diagnosis should go for a routine eye examination, at least once every year. Doing so will pick up any eye complications while they are still minor.
Regular diabetes eye checks
The annual eye check is not done by a regular doctor or an optician. Instead, it is a specialist examination by an optometrist or an eye doctor called an ophthalmologist. An eye doctor can then treat any problems that are found. 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 check is known as the dilated eye exam, and it detects the signs of diabetic retinopathy - disease of the retina caused by diabetes.
If diabetic eye problems are known to have developed already, multiple follow-up checks will be recommended to take place every year.
A woman with diabetes who becomes pregnant should also have more regular checks. The Merck Manual recommends one check for each trimester of pregnancy.
Long-term eye problems
Eye complications caused by diabetes are progressive. They can start at a point where they are found only by a specialist eye examination, before any eye or visual symptoms appear.
Eye disease caused by diabetes gets worse over time without treatment.
Retinopathy has the potential to progress onto increasingly worse states. Broadly, there are two stages of this eye disease:
- Background retinopathy, or non-proliferative diabetic retinopathy (NPDR) - early stages, with no symptoms, or only mild ones
- Proliferative diabetic retinopathy (PDR) - advanced stages of eye complications
With NPDR, the retina's tiny blood vessels may be weakened 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 classed as mild, moderate, or severe based on the extent of the blood vessel problem.
Swelling in the retina is known as macula edema. It can cause vision problems because it is the central part in the back of the eye that allows people to see fine details clearly.
PDR, the more advanced stage of eye disease that can be caused by diabetes, results from blood vessel problems. Vessels fail to get blood to the retina because they have closed up, and new vessels start to grow to compensate for this. This stage only develops in some people with diabetes and 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. If this is severe enough, vision can become distorted. The retina can even become detached, causing a loss of vision.
The fragile new vessels can also bleed out. Symptoms of this can include floating spots in the vision. If a bleed from the retina into the central fluid of the eye is big, sight can sometimes be lost, leaving only the ability 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 is the result - a buildup of pressure in the eye that can affect the main nerve going from the eye to the brain.
The goal of regular eye checks for people with diabetes is to find problems with the retina at the earliest stages. It is good news if diabetes is well-controlled and no changes to the back of the eye can be seen for a number of years.
Keeping blood sugar levels under control is important for treating eye problems caused by diabetes.
When it is found at its earliest stages, retinopathy can be managed with monitoring and controlling those things that can affect eye health, such as high blood sugar level and high blood pressure.
Preventive measures can then be started in time to slow down the condition. Otherwise, retinopathy is a progressive condition that gets worse if blood sugar levels remain too high.
Problems with the retina can be prevented by bringing sugar levels under control. Keeping tight control of blood sugar levels also slows down any retinopathy that has already been found.
The diet and lifestyle measures that are needed to manage diabetes are the same measures that prevent eye problems. Any further medical help for diabetes also controls the risk for eye complications.
Good blood sugar control also helps to keep another risk factor for eye problems under control - high blood pressure (hypertension).
Preventing high blood sugar levels can have wider benefits against other diabetes complications, too. Diabetic neuropathy, which can cause loss of sensation throughout the body, is due to damage to nerves due to high blood sugar levels.
Prevention with regular checks and strict diabetes management is better than managing the complication once it occurs. But if retinopathy does reach the later stages of progression, specific eye treatments may be needed.
Eye doctors may recommend:
- Injections in the eye
- Laser surgery on the back of the eye - used to reduce swelling at the center of the retina, to shrink or prevent abnormal blood vessel growth, and prevent bleeds
- Microsurgery in the eye
Other causes of blurry vision
Aside from diabetes, other causes of blurriness include a simple worsening of eyesight without any medical condition behind it.
Such blurred eyesight can be because of near-sightedness or far-sightedness. Blurriness resulting from a lack of 20/20 vision can be corrected.
Another common cause of blurriness is from dry eyes. 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.
Changes to lighting, blinking more, and taking breaks are ways to prevent dry eyes. It is important to get an eyesight check from an optometrist, too.
Medical causes of blurred vision include cataracts and glaucoma. Cataract and glaucoma are both more likely to develop in people who have diabetes.
Sometimes blurred vision can occur after exercising or after a hot bath because of a condition called optic neuritis. Other symptoms include dim vision, dulled or fading perception of color, and pain behind the eye when moving the eyes. If you experience these symptoms, you should see a doctor.
There are numerous other medical reasons for blurry vision, aside from diabetes, cataracts, and glaucoma. Anyone with eye or vision symptoms should always consult a doctor.