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Blurry vision and diabetes

A hand holds a magnifying glass over the words "blurred vision," which are above a background of many other symptoms of diabetes

Blurry vision can be due to diabetes — even if you’re not aware you have the disease.

Diabetes can cause temporary or permanent changes in the lens and the retina of the eye, depending on how severe the condition is and how long you’ve had it.

Hyperglycemia and hypoglycemia

The blood sugar spikes (hyperglycemia) associated with diabetes is a common cause of blurred vision among diabetics. When blood sugar levels are too high, the lens inside the eye retains water and starts to swell.

The normally clear lens sits directly behind the pupil and helps you focus on objects. Since light has to pass through the lens before it can be focused on the retina, the result of this swelling is blurry vision. 

Low blood sugar (hypoglycemia) can also lead to blurry vision, but for an entirely different reason. Instead of directly affecting your eye, low blood glucose can temporarily affect the way your brain receives and interprets your vision. This is what causes your eyesight to appear blurred.

These forms of blurry vision make the world around you appear out of focus and harder to interpret. If you wear prescription glasses or contact lenses, the effect can be similar to what you might experience when you aren’t wearing your corrective lenses.

In these cases, your level of blurry vision will be roughly the same in the morning, at night and throughout the day.

Blurry vision can be experienced by people with Type 1 or Type 2 diabetes. Although each type of the disease has a unique effect on insulin and a different underlying cause, Type 1 and Type 2 diabetes can both raise and lower your blood sugar. When it shifts to an abnormal level, blurred vision can follow.

Does blurry vision from diabetes go away?

Experiencing blurry vision as a result of diabetes can feel unsettling. Naturally, one of the first things you might ask yourself is how long it’s going to last.

When the visual disturbance is caused by hyperglycemia or hypoglycemia alone, your blurry vision should go away with time and regulation of your blood sugar. It can take several weeks for your blood sugar level — and with it, your vision — to return to normal. But the effect may only be temporary.

Blurred vision can come and go any time your blood sugar level fluctuates. If you have diabetes and experience blurry vision (even if it goes away), speak with your doctor.

Diabetic eye conditions that can cause blurred vision

While blurry vision due to blood sugar levels is mostly temporary, diabetes can also lead to separate, more serious eye conditions.

Diabetes can cause damage to the retina and blood vessels in the back of the eye. This is known as diabetic retinopathy. Blurred vision is a symptom, but people usually experience fluctuating vision instead of a constant blur.

The term “retinopathy” means that the retina has been damaged in some way. When the retina is damaged, blurry vision, and eventually vision loss, can occur.

When this happens, blurry vision will not go away. But with the help of diabetic retinopathy treatment, damage can often be slowed or stopped, reducing the risk of any further vision loss.

Cataracts, another common cause of blurry vision, can also occur when blood sugar changes due to diabetes cause the lens of the eye to become cloudy over time. Blurred vision tends to be one of the earlier signs of cataracts, along with slightly fading colors, increased glare and difficulty seeing at night.

Less commonly, diabetes can also lead to a serious form of glaucoma called acute angle-closure glaucoma. It happens when the pressure inside your eye rises very quickly.

In addition to blurry vision, angle-closure glaucoma can cause very noticeable, immediate symptoms, including severe eye pain, nausea and vomiting. If this happens to you, seek medical care immediately.

SEE RELATED: Different types of diabetic eye problems

Keep in touch with your eye doctor

Frequent check-ups with your eye doctor are critical to ensuring any eye damage is diagnosed and treated as early as possible. Retinopathy can start long before you notice visual symptoms, including blurry vision.

Be sure to schedule a comprehensive eye exam with an optometrist or ophthalmologist if you have diabetes and haven’t seen an eye doctor in a while.

READ MORE: What is a diabetic eye exam?

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