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What Causes Blurred Vision?

Dr. Jordan Marr

Written By:

Dr. Jordan Marr

Updated: 30 September 2022 •  

Are you struggling to read signs? Or maybe you see ‘starbursts’ at night.
 
Most people experience a form of blurred vision at some point in their life. The fix can be as simple as putting on a pair of glasses. But sometimes, the cause can be something more serious.
 
It’s important to know when your blurred vision needs some extra attention. The tricky part is that blurred vision can have many causes, and can present in many ways.
 

What does blurred vision feel like?

Blurred vision makes things appear fuzzy and out of focus and looks like a “soft focus” filter. This can happen up close, far away, or at all distances.
 
Blurred vision is different to having double vision, distorted vision, or a blind spot (i.e. a missing or dark area in your vision). Many people also confuse blurred vision with cloudy vision, where colors look muted, and everything is hazy and foggy. However, these are all distinct conditions.
 
blurred-vision

Today, we’ll be discussing the causes of blurred vision.

 

When blurred vision is a simple prescription fix

Most cases of blurred vision are caused by an existing refractive error. This refers to an imperfection in the shape of your eye and can be corrected with glasses or contact lenses.
 
Myopia, or short-sightedness, happens when your eyeball is too long, which causes objects in the distance to become blurred while objects up close remain clear. This is because light is focusing in front of the retina (the light sensitive layer in the back of your eye).
 
long eyeball causes myopia

Source: Britannica

 
On the other hand, people who are long-sighted (also known as hyperopia) have shorter eyeballs and struggle to see things up close because light focuses behind the retina.
 
You may also have astigmatism, where your cornea (the front of your eye) isn’t perfectly round and causes blurred vision at all distances. Astigmatism is more obvious when driving at night, as headlights and streetlights look scattered – often described as ‘starbursts’.
 
If you’re experiencing blurred vision and you have myopia, hyperopia, or astigmatism you will likely need glasses or contact lenses to fix it. Your eye doctor will conduct an eye exam to determine your prescription – a document that you’ll reference when buying a pair of glasses. Many eyeglass retailers, like Mouqy, offer a wide range of frames to suit any taste and lifestyle.
 
If you’re not into glasses, you could consider looking into surgical options like LASIK.
 
As we get older, it gets harder and harder to focus on nearby objects, causing most of us to pull our phones further away to read them. This is called presbyopia which begins in your 40s and progresses until your mid-60s. As with everything else in our bodies our focusing system weakens as we age.
 
If this sounds like you, you might be in need of some reading glasses while doing up-close tasks.
 

Other causes for blurred vision

Sometimes it’s not quite as simple as getting new glasses. Other causes could include:
 

  • Cataracts cause blurred vision which is worse at night and may make you more sensitive to glare. Lots of people with cataracts see “halos” around lights and their vision appears faded and yellowed. Cataracts can occur with age but can also be caused by an eye injury, medication, or something you are born with. Some cataracts cause complete blurred vision while others will only blur part of your vision. When cataracts become severe, they can be removed by an ophthalmologist.
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  • Migraines can cause blurred vision, blind spots, and distorted auras that look like a kaleidoscope. Flashes, tunnel vision, and shimmering zig-zag lines are also common in migraines. Most of the time migraines affect both eyes, so if you experience vision changes in only one eye it’s a good idea to see an optometrist to rule out other causes.
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  • Dry eyes can make your eyes irritated, watery, and blurred. Having dry eyes can change the surface of your tear film (the tear layer coating the front of your eye) and distort your vision. Usually using lubricating drops helps, but if it persists you should seek medical advice.
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  • Pregnancy causes fluid retention which can change the shape of your cornea and cause distorted vision. Usually, this goes away after pregnancy and your eyes return to normal. If the blurred vision is only mild and doesn’t bother you, you may not need glasses to fix this. However, if your blurred vision is accompanied by temporary vision loss, light sensitivity, or flashes of light, you should seek medical help as it could be a sign of preeclampsia.
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  • Eye injuries might damage and distort the front of the eye, causing blurred vision. In more severe injuries you might notice flashes of light or floaters (squiggly dark spots) in your vision and your vision could be doubled. Minor eye injuries can be treated with cold compresses, flushing the eye, or eyedrops, but if you have changes to your vision after a head or eye injury, it’s important to be assessed as soon as possible to make sure that everything is okay.

 

When might blurred vision be a sign of something serious?

Sometimes blurred vision can be a sign of something more serious that may lead to permanent vision loss or significant health risks. These include:
 

  • Glaucoma causes a gradual loss of peripheral vision, which can eventually lead to tunnel vision and even blindness. Performing daily tasks can be difficult for people with glaucoma due to blurred vision, glare sensitivity, blind spots in their vision, and colors appearing dull.
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  • Diabetic retinopathy happens when the eye doesn’t have enough blood circulation and makes new blood vessels which are very weak and leak into the retinal tissue in the back of the eye. This makes the retina swell and causes blurred vision. If this happens for a long time, scar tissue can form which causes permanent vision loss and even retinal detachment.
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  • Age-related macular degeneration (AMD) is a common cause of permanent vision loss in people aged over 55 years. As AMD progresses, it can cause a patch of blurred central vision which gets bigger without treatment. You might also have trouble seeing things under dim light and you may find that straight lines appear distorted and wavy.
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  • Retinal detachment is when the retina pulls away from the choroid (the tissue underneath the retina that provides oxygen and nutrients to the eye). This will make your vision very blurred, and you might notice lots of new floaters, flashes of light, or a dark “curtain” in your vision (which is your retina folding over). If you have these symptoms, you must seek urgent medical help as this progresses quickly and there is a risk of permanent vision loss.
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  • Systemic conditions can also present with blurred vision alongside other symptoms. Some serious conditions that may be responsible for your blurred vision are multiple sclerosis, stroke, or cardiovascular disease. Typically, these are accompanied by other symptoms such as dizziness, weakness or numbness in the arm, headaches, or vision loss.

 

Can blurred vision be prevented?

The most effective way to prevent blurred vision is by having regular eye exams so that any simple or more serious conditions can be picked up on and treated sooner. This is especially important if people in your family have eye conditions.
 
It’s also important to take care of your general health by exercising regularly, eating a rich diet (omega-3 and leafy greens are important!) and avoiding common risk factors such as smoking.
 
For the most part, blurred vision can be prevented, but sometimes it’s just a part of ageing or it’s simply due to your genetics, especially when it comes to refractive errors.
 
In saying that, in recent years a lot of research has indicated that taking regular breaks from near work and spending time outdoors can help prevent short-sightedness in children.
 
Specialized spectacle lenses, atropine (a type of eye drop), and orthokeratology (a contact lens that reshapes your cornea in your sleep) among other options have also shown to be effective in controlling myopia.
 

When to see a doctor about your blurred vision

If you experience a sudden onset of blurred vision, or persistent blurred vision, along with any of the following signs, you should seek medical help:
 

  • Severe eye pain
  • Headaches
  • Complete or partial vision loss
  • Weakness/numbness in one arm
  • Dizziness or loss of balance
  • Drooping face
  • Slurred speech

 
If in doubt, it never hurts to see a professional to put your mind at ease!
 

References

  • “Refractive Errors”, National Eye Institute
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  • “Prevalence, Risk Factors, and Impact of Undiagnosed Visually Significant Cataract: The Singapore Epidemiology of Eye Diseases Study”, Plos One
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  • “Ocular Changes During Pregnancy”, Journal of Current Ophthalmology
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  • “Symptoms Related to the Visual System in Migraine”, F1000 Research
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  • “Dry Eye”, American Optometric Association
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  • “Eye Injuries”, Cleveland Clinic
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  • “What Do Patients with Glaucoma See? Visual Symptoms Reported by Patients with Glaucoma”, The American Journal of the Medical Sciences
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  • “Diabetic Retinopathy”, American Optometric Association
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  • “Age-Related Macular Degeneration”, National Eye Institute
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  • “Retinal Detachment”, National Eye Institute
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  • “Blurred Vision”, British Medical Journal
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  • “Nutrition and Eye Health”, Nutrients
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  • “Myopia Treatments: How to Choose and When to Use?”, Review of Optometry
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  • “Red Flags in Neuro-Ophthalmology”, Community Eye Health Journal
Dr. Jordan Marr

Written by:

Dr. Jordan Marr

Dr Jordan Marr has over 5 years of clinical and academic optometry experience and is a visual science editor for the Clinical and Refractive Optometry journal. He is licensed under the Optometry Board of Australia.
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