Diabetes and blurry vision
Blurry vision can be one of the earliest symptoms of diabetes. It may come and go or remain constant. Understanding why it happens is key to protecting your sight.
Why diabetes can cause blurry vision
Changes in blood sugar levels can affect how your eyes focus.
- High blood sugar levels (hyperglycaemia): When glucose levels are too high, fluid moves in and out of the eye, causing swelling. This changes the lens shape, which can lead to blurry vision. Once blood sugar levels return to normal (typically 70–130 mg/dL before meals), vision usually clears.
- Low blood sugar levels (hypoglycaemia): When blood sugar levels dip below 70 mg/dL, it can temporarily affect brain and eye function, leading to blurred vision. Thankfully, in most cases, clear vision will return once your blood sugar levels return to normal.
- Fluctuating blood sugar: Frequent fluctuations can cause recurring blurry vision and can lead to uncomfortable symptoms and may be harmful to your health, leading to diabetes complications. It is important to talk to your doctor about strategies to keep your blood sugar stable.
How diabetes affects the eyes
If you have diabetes, you’re at an increased risk of sight loss. That’s because, to work properly, the eye needs a constant supply of blood. When control of blood sugar and insulin levels in the body is poor, the blood vessels of the eye may become damaged. This can cause blurry vision and, if left untreated, potential vision loss.
Make sure to attend your diabetic eye screening appointments when invited; it is vital for detecting early signs of damage and reduce your risk of vision loss. If you have any concerns regarding your vision, speak with your doctor.
Key eye conditions linked to diabetes
Diabetic retinopathy
The most common diabetes-related eye condition is diabetic retinopathy. This can occur when high blood sugar levels cause damage to the retinal blood vessels.
Diabetic retinopathy can cause blood vessels to leak, or can cause new weaker blood vessels to grow, which can lead to complications. When blood vessels leak in the macula area, this is known as diabetic macular oedema.
Diabetic macular oedema
Diabetic macular oedema (DMO) also referred to as diabetic macular edema (DME) occurs when blood vessels in the macula start to leak, causing fluid to build up in the macula, leading to swelling.
This can cause blurred vision or central vision loss, as the fluid and leaking blood vessels interrupt how well the photoceptors in the macula work. DMO/DME is the most common cause of sight loss in people with diabetes.
Symptoms include:
- Dark spots like a smudge on glasses or gaps may appear in your vision, especially first thing in the morning
- Objects in front of you might change shape, size or colour or seem to move or disappear
- Colours can fade
- You may find bright light or glare difficult
- You may experience difficulty reading
- Straight lines such as door frames and lamp posts may appear distorted or bent.
DMO can be a progressive condition, meaning symptoms only become noticeable as the disease progresses.
In the early stages, a person may not notice any effect on their vision, as damage to the retina occurs over many years.
DMO can be treated with injections of a drug called anti-vascular endothelial growth factor (anti-VEGF), which help stop fluid build up in the macula and protect vision.
When to be concerned about blurry vision
We know how unsettling it can be to experience changes to your eyesight. But it’s important to understand that although blurry vision is often linked to diabetes, it doesn’t always mean permanent damage.
It’s vital to attend your diabetes clinic appointments. Your diabetes care team can then maintain and monitor your eye health and spot any problems early. And if you wear glasses or contact lenses, continue to visit your optician regularly and tell the optometrist that you are diabetic.
Contact your optometrist or hospital eye specialist urgently if you notice:
- Sudden vision loss or distortion
- Dark spots, flashes, or blank areas in your sight
- Straight lines appearing bent
What to expect at a diabetic eye exam
At your diabetic eye screening, the healthcare professional will:
- Check your vision and take a brief medical history
- Administer eye drops to dilate the pupils
- Take pictures of the retina to detect any changes in the blood vessels.
These eye drops can cause blurred vision for a few hours after use, so it’s recommended not to drive after this.
The photos of the eye are then read by a qualified retinal grader, who will look for signs of retinopathy or macular oedema.
You will be sent the results of your screening and be referred to an eye specialist if there are any changes detected in the retina.
Protecting your vision with diabetes
Diabetes is a lifelong condition, so maintaining a healthy lifestyle and monitoring your blood sugar, blood pressure and cholesterol levels is crucial to avoid damage to your eyes.
You can help to protect your eyes by:
- Monitoring your blood sugar levels regularly, aiming to keep within limits recommended by your doctor or nurse
- Maintaining a healthy weight and blood pressure
- Eating plenty of fruit and green vegetables
- Exercising regularly
- Avoid smoking and limiting alcohol
- Attending all diabetic eye screening and routine eye appointments
Looking for more information about diabetes?
Diabetes UK provides expert information, guidance and support for people living with diabetes. Visit their website to learn more about managing diabetes and understanding how it can affect your health, including your eyes.
Frequently asked questions
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Can blurry vision be the an early sign of diabetes?
Yes, blurry vision is often one of the first symptoms. Fluctuations in blood sugar affects the lens of the eye, changing its shape and focus.
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Will my blurry vision go away once I manage my blood sugar?
In many cases, yes. Once glucose levels stabilise, vision often returns to normal. However, if vision changes persist or worsen, it’s important to seek medical advice, as this could indicate a more serious eye condition related to diabetes.
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How often should I have an eye exam if I have diabetes?
You should have a comprehensive diabetic eye exam every one or two years. Some people may need more frequent checks depending on their eye health and diabetes control. Additionally, it is recommended to visit your optometrists at least every few years.
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What’s the best way to prevent diabetic eye damage?
Consistent blood sugar control and regular eye care along with getting your eyes checked regularly are essential to preventing long-term damage to your vision.
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Can low blood sugar cause blurry vision too?
Yes, when levels drop too low, it affects brain and eye function. This should resolve once your blood sugar returns to a normal level.
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What is diabetic retinopathy, and why is it serious?
Diabetic retinopathy is a complication of diabetes that affects the blood vessels in the retina. High blood sugar levels over time can damage these vessels, causing them to leak or become blocked. If left untreated, diabetic retinopathy can lead to vision loss.
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What is DMO and how does it affect vision?
Diabetic macular oedema (DMO), also known as diabetic macular edema (DME), occurs when damaged blood vessels leak fluid into the macula. This causes swelling and can lead to blurred or distorted vision. DMO can be a progressive condition, meaning symptoms might not appear until the disease is more advanced.
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When should I seek help for blurry vision?
If you notice sudden changes in your vision, dark spots, flashes of light, distorted lines or a significant loss of sight, contact your optometrist or an eyecare specialist immediately, even if your symptoms seem to improve later.
Diabetic macular oedema (DMO)
Macular oedema (MO) is swelling of the retina at the back of the eye in the macular area usually due to fluid build-up from leakage of damaged or abnormal blood vessels.
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