SymptomEyes & vision
Blurred Vision: Causes and When to Worry
Blurred vision means things look out of focus, hazy or smeared, so fine detail is lost. The most common causes are uncorrected focusing problems (nearsightedness, farsightedness, astigmatism and age-related presbyopia), dry eyes and cataracts, which develop gradually. Sudden blurred vision, especially in one eye or with eye pain, a headache, flashes, a curtain over vision or weakness, can signal stroke, acute glaucoma or retinal detachment and needs emergency care.
Also called: Blurry vision, cloudy vision, hazy vision, fuzzy vision, loss of visual sharpness
At a glance
- What it is
- Loss of sharpness so objects look out of focus or hazy.
- Common causes
- Need for glasses, presbyopia after 40, dry eyes, cataracts, eye strain.
- Serious causes
- Stroke, acute angle-closure glaucoma, retinal detachment, optic neuritis, uncontrolled diabetes.
- Key questions
- Sudden or gradual? One eye or both? Painful or painless?
- Diagnosis
- Vision chart, eye pressure, slit-lamp and dilated retinal exam.
- Treatment
- Glasses or contacts, eye drops, cataract surgery, or treating the underlying disease.
When to get help
Call 911 or go to the ER
- Sudden blurred or lost vision with face drooping, arm or leg weakness, slurred speech or confusion (possible stroke): call 911 or your local emergency number
- Sudden vision loss or a dark curtain or shadow moving across vision in one eye
- Sudden blurred vision with severe eye pain, a red eye, halos around lights, headache and vomiting (possible acute glaucoma)
- A shower of new floaters or flashes of light with blurring
- Blurred vision after a chemical splash or a blow to the eye
See a doctor within a day or two
- New blurred vision in one eye over hours to days, especially with pain on moving the eye (possible optic neuritis)
- Blurred vision with a new headache and scalp tenderness or jaw pain on chewing in someone over 50 (possible giant cell arteritis)
- Blurred vision with severe headache or swelling in pregnancy (possible preeclampsia)
- Blurred vision with a painful, red, light-sensitive eye, especially if you wear contact lenses
- Blurred vision with very high blood sugar, extreme thirst or confusion
Book a routine appointment
- Gradually worsening blur when reading, driving or watching TV
- Glare or halos at night and colors looking faded
- Wavy or distorted straight lines, or a blurry spot in the center of vision
- Blurred vision that comes and goes with known diabetes
Usually safe to manage at home
- Brief blur after long screen use that clears with blinking and breaks
- Mild blur with gritty, dry eyes that improves with artificial tears
What blurred vision is
Clear vision depends on light being focused sharply on the retina, the light-sensitive layer at the back of the eye, and on healthy nerves carrying the signal to the brain. Blurred vision happens when any of these steps fails:
- Focusing errors: the eye is the wrong shape or the lens has lost flexibility.
- Cloudiness: the tear film, cornea or lens is not clear.
- Retina problems: swelling, bleeding or detachment of the retina.
- Nerve and brain problems: optic nerve inflammation or stroke.
People sometimes say "blurred" when they mean double vision, which is seeing two images. Cover one eye: if double vision goes away, it is usually from the eye muscles or nerves, not focusing.
Common causes of blurred vision
Refractive errors (the need for glasses)
| Condition | What is blurry | Notes |
|---|---|---|
| Myopia (nearsightedness) | Distant objects | Often starts in childhood, worsens through teen years |
| Hyperopia (farsightedness) | Near objects, sometimes all distances | Can cause eye strain and headaches |
| Astigmatism | All distances, with smearing or ghosting | Uneven curve of the cornea |
| Presbyopia | Near objects like menus and phones | Starts around 40 to 45 in everyone |
These are corrected with glasses, contact lenses or laser surgery.
Dry eyes and eye strain
Dry eye causes blur that fluctuates and improves with blinking, along with grittiness, burning or watering. Long screen use reduces blinking. The 20-20-20 rule helps: every 20 minutes, look at something 20 feet (6 m) away for 20 seconds.
Cataracts
A cataract is clouding of the lens, very common after 60. Vision becomes gradually hazy, colors fade, and glare from headlights worsens. Cataract surgery restores clear vision in most people.
Diabetes
High blood sugar makes the lens swell, causing blur that fluctuates with glucose levels. It often improves within weeks once sugar is controlled. Long-term diabetes damages the retina's blood vessels (diabetic retinopathy) and can cause macular swelling, a common cause of vision loss. Yearly dilated eye exams catch it early.
Age-related macular degeneration
Macular degeneration affects central vision after age 50. Straight lines look wavy, and a blurry or dark spot appears in the center. The "wet" form can progress quickly and is treated with eye injections, so new distortion needs a prompt eye exam.
Other common causes
- Eye infections and inflammation: conjunctivitis (usually mild blur from discharge), keratitis and uveitis (pain, redness, light sensitivity).
- Migraine: visual aura with shimmering zigzags or blind spots for 5 to 60 minutes, often followed by headache. See migraine.
- Medicines: antihistamines, some antidepressants, steroids and drugs such as hydroxychloroquine.
- Pregnancy: fluid changes can blur vision slightly, but blurred vision with headache or swelling needs urgent preeclampsia checks.
Sudden blurred vision: serious causes
| Cause | Typical features |
|---|---|
| Stroke or TIA | Sudden loss in one eye or one side of vision, with other stroke signs |
| Retinal detachment | Flashes, a burst of floaters, then a shadow or curtain spreading across vision |
| Acute angle-closure glaucoma | Severe eye pain, red eye, halos, headache, nausea, cloudy cornea |
| Optic neuritis | Blur in one eye over hours to days, pain when moving the eye, faded colors; linked to multiple sclerosis |
| Giant cell arteritis | Age over 50, new headache, scalp tenderness, jaw pain; can cause permanent blindness |
| Retinal vein or artery blockage | Sudden painless blur or loss in one eye |
| Bleeding in the eye | Sudden floaters or red haze, often in diabetes |
Blurred vision in one eye vs both eyes
Blur in one eye points to a problem in that eye or its optic nerve: retinal detachment, a blocked retinal blood vessel, optic neuritis or a cataract. Blur in both eyes is more often from refractive error, dry eyes, diabetes, medicines, migraine or a problem in the brain. Check by covering each eye in turn.
Blurred vision and headache
Blurred vision with headache occurs with migraine, eye strain, high blood pressure crises, acute glaucoma, giant cell arteritis, preeclampsia and, rarely, raised pressure inside the skull. A sudden, severe headache with vision change needs emergency care.
How doctors find the cause
An eye doctor (optometrist or ophthalmologist) will:
- measure sharpness with a letter chart, with and without a pinhole (blur that improves with a pinhole is usually a focusing problem)
- check pupils, eye movements and side vision
- measure eye pressure
- examine the front of the eye with a slit lamp
- dilate the pupils to examine the retina and optic nerve
- sometimes order an OCT scan (a detailed image of the retina) or a visual field test
Blood sugar, blood pressure and blood tests for inflammation may also be checked.
Treatment for blurred vision
- Refractive errors: glasses, contact lenses or refractive surgery.
- Dry eyes: preservative-free artificial tears, warm compresses, screen breaks and treating eyelid inflammation.
- Cataracts: surgery replacing the cloudy lens with a clear implant.
- Diabetes: blood sugar control; laser, injections or surgery for retinopathy.
- Wet macular degeneration: anti-VEGF eye injections.
- Glaucoma: eye drops, laser or surgery; acute angle-closure needs emergency treatment.
- Retinal detachment: urgent surgery.
- Infections and inflammation: antibiotic, antiviral or steroid drops.
Preventing vision problems
- Have regular eye exams: every 1 to 2 years after age 40, and yearly with diabetes.
- Wear UV-blocking sunglasses and safety glasses for risky tasks.
- Control blood sugar, blood pressure and cholesterol, and do not smoke.
- Follow contact lens hygiene, and never sleep or swim in lenses unless designed for it.
Frequently asked questions
What causes sudden blurred vision?
Sudden blurring can be caused by stroke, retinal detachment, acute glaucoma, optic neuritis, a blocked blood vessel in the eye, migraine aura or very high blood sugar. Sudden blur in one eye, with pain, flashes, a curtain or weakness, is an emergency.
When should I worry about blurred vision?
Worry if blurred vision comes on suddenly, affects one eye, or comes with eye pain, a red eye, headache, flashes, a shadow over vision, weakness or speech trouble. Gradual blur over months is less urgent but still needs an eye exam.
Can high blood sugar cause blurred vision?
Yes. High blood sugar makes the eye's lens swell and changes its focus, causing blur that comes and goes. It usually improves within a few weeks once glucose is stable. Long-term diabetes can damage the retina, so people with diabetes need yearly dilated eye exams.
Can stress or anxiety cause blurred vision?
Anxiety can cause brief blurring through tense eye muscles, fast breathing or dry eyes, and it usually clears as you calm down. Persistent or one-sided blur should not be put down to stress without an eye exam.
Why is my vision blurry in one eye?
Blur in one eye suggests a problem in that eye or its nerve, such as a cataract, dry eye, infection, retinal detachment, a blocked retinal vessel or optic neuritis. If it came on suddenly or with pain or flashes, seek emergency care.
Can dehydration cause blurry vision?
Dehydration can reduce tear production and cause dry, blurry eyes, and severe dehydration can cause dizziness and visual dimming. Drinking fluids and using artificial tears usually helps. Blur that persists after rehydration needs an eye exam.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Ophthalmology: Blurry vision causes; Eye health A-Z
- National Eye Institute (NEI): Eye conditions and diseases
- NHS: Blurred vision
- American Stroke Association: Stroke warning signs (BE FAST)
- MedlinePlus: Vision problems