Blurred vision

Blurred vision, also described as clouded or dimmed vision, can: 

• Affect all or part of your sight — this may include your left or right field of vision and/or your peripheral vision
• Affect only one eye
• Be the result of a minor problem or something more serious
• Come on gradually or suddenly

Most cases are treatable but it’s important to pinpoint the cause.

There are many possible reasons for blurred vision.

Eyesight problems

• Eye strain — caused by looking at something, such as your computer screen, for a long time, or wearing the wrong prescription glasses or contact lenses
• Refractive errors — these can usually be treated with contact lenses, glasses and/or surgery, and include:
• Astigmatism — a distortion of your vision that can make objects at all distances appear blurry, which is usually caused by the front surface of your eye (cornea) being misshapen 
• Hyperopia — this is also known as long-sightedness and causes objects in your near vision to appear blurry; other symptoms include eye strain and fatigue
• Myopia — this is also known as short-sightedness, is the most common refractive error and causes objects in the distance to appear blurry; other symptoms include eye strain, headaches and squinting
• Presbyopia — age-related loss of your near sight caused by the lenses inside your eyes hardening 
• Wearing your contact lenses for too long — this can cause debris in your tear film (the liquid layer that covers the surface of your eye) to build up on your contact lenses

Conditions

• An eye infection
• Eye diseases — eg age-related macular degeneration (AMD), cataracts, diabetic retinopathy or glaucoma
• Eye-related conditions — this includes:
• Dry eye syndrome — long-term (chronic) dryness of your eyes, which can be treated with lubricating eye drops or in more severe cases, prescription medications or punctal plugs to block your tear ducts
• Eye floaters — very small bits of tissue, which develop with age as the gel-like substance in your eye becomes more liquid, and drift into your vision; if you experience a sudden increase in the number of floaters in your eye this may be a sign that your retina (the back part of your eye) is detached or torn and you should see your optometrist urgently 
• Ocular migraines — reduced blood flow to the eye or spasms in the blood vessels that supply the back of your eye, which cause temporary blurred vision or blind spots, and sometimes occurs after or with a migraine
• Pterygium — a non-cancerous growth on the eye’s surface, which can change the shape of your cornea 
• Hypoglycaemia — this is more common in people with diabetes who are taking medication to lower their blood sugar levels
• Non-eye-related conditions — this includes: 
• A brain tumour — this is a rare cause of blurred vision
• Migraine
• Optic neuritis — inflammation that damages your optic nerve, which carries information from your eyes to your brain
• Rosacea
• Stroke

Other causes

• Laser eye surgery — this is usually carried out to correct refractive errors and can cause blurred vision immediately after surgery
• Pregnancy — blurred vision is common during pregnancy due to changes in your hormones affecting the shape and thickness of your cornea; this is not usually serious but in some cases may suggest high blood pressure or gestational diabetes
• Side effects of medication — certain allergy pills can cause dry eyes and certain eye drops can irritate your eyes; dry or irritated eyes can both cause blurred vision
• Trauma or injury — this includes accidentally getting chemicals in your eye, detachment of your retina and scratches to your cornea

Age-related macular degeneration (AMD)

The cone cells on the macula (a part of your eye that’s vital for seeing) become damaged, leading to loss of central vision. There are two main types: dry AMD, which progresses slowly but is untreatable, and wet AMD, which progresses more rapidly but is treatable, especially if spotted early.

Cardiovascular disease

Blurred vision that occurs with double vision can be a sign of a health emergency, such as a brain haemorrhage or stroke. 

Cataracts

A cataract is the gradual clouding of your lens, which is a transparent disc behind your iris (the coloured part of your eye). It’s common in people over 65, though it can happen earlier. Besides blurred vision, symptoms include sensitivity to light and a dulling effect on colours. Luckily, it’s easily treated with cataract surgery.

Diabetes

Over time, diabetes can lead to a condition called retinopathy, when the tiny blood vessels at the back of your eye become blocked and leak. This damages your retina, which is essential for vision and can lead to sight loss. However, it can be prevented if detected early through regular screening.

Glaucoma

There are four types of glaucoma, which can lead to a build-up of pressure in your eye, damaging the optic nerve. This can permanently damage your sight, especially your peripheral vision, but once it’s detected, sight loss can usually be prevented.

Multiple sclerosis

This is an autoimmune disease that causes your body to attack the protective coating that wraps around your nerve cells, causing these cells to become damaged. Vision problems are very common in people with multiple sclerosis and include blurred and double vision.

It’s important to get a diagnosis for blurred vision as soon as possible, especially if it's come on suddenly and/or you have other symptoms. See your optometrist or GP for further investigations.

They will ask you questions to determine your exact symptoms, such as when you first noticed your vision was blurry and what makes your blurred vision better or worse. They may also ask about your medical history and your family's medical history. 

Next, they may examine your eyes and check your vision by asking you to read an eye chart. Other investigations they may carry out include: 

• Blood tests — to check for infection 
• Ophthalmoscopy
• Refraction test
• Slit-lamp examination
• Tonometry — to measure the pressure in your eye

Go straight to your nearest A&E department if you also have:

• A sudden change in your vision
• Facial drooping, problems speaking or loss of muscle control
• Had an accident affecting your eyes
• Severe eye pain
• Severe headache
• Visual disturbances, such as flashing lights, halos, shadows or spots

Some of these symptoms overlap with the symptoms of a stroke. 

• Facial drooping, problems speaking or loss of muscle control

Treatment depends on the cause. They may include:

• Corrective glasses or contact lenses for refractive problems, such as short and long sight, astigmatism and presbyopia
• Eye drops for dry eye syndrome, infections, and other conditions
• Foods containing fast-acting sugars, such as juices and sweets, if the cause is low blood sugar levels
• Medication, injections or sometimes laser treatment for various eye conditions including diabetic retinopathy and glaucoma
• Painless drug injections into the eye for wet AMD to prevent further damage
• Surgery to remove cataracts

If an underlying health condition, such as a migraine, is the cause of your blurred vision, you will receive treatments specific to your condition. 

If eye strain or wearing your contact lenses for too long is the cause of your blurred vision, your optometrist or GP may offer lifestyle advice.

Some causes of blurred vision can't be prevented. However, you can reduce your risk of blurred vision caused by lifestyle factors. You can:

• Always wear sunglasses with UV protection when you are outside in the sun
• Eat a diet rich in nutrients that are good for your eyes — this includes: 
• Omega-3 fatty acids found in canned, light tuna, halibut, salmon and trout
• The antioxidant lutein found in dark, leafy greens eg kale and spinach
• Vitamin A found in carrots, liver and sweet potatoes
• Have regular eye exams at the opticians — this is particularly important if someone in your family has a history of eye disease, such as glaucoma
• Stop smoking
• Wash your hands before touching your contact lenses to reduce the risk of eye infections
• Wear protective eyewear when carrying out DIY or using heavy machinery