Blurry Vision in One Eye but the Other Is Fine? Common Causes Explained

Sometimes it's only noticed by chance. You cover one eye while rubbing it, and suddenly the world looks hazy through the other. Or reading has become harder, and you realise one eye is doing most of the work.

Blurry vision in one eye is a surprisingly common complaint. Because the stronger eye compensates, many people don't notice the change for months. The cause can be as simple as needing new glasses, or it can point to a condition in the lens, retina or optic nerve that benefits from early treatment.

Quick Answer

Blurry vision in one eye is most often due to an uncorrected refractive error, a developing cataract, or dry eye affecting one side more. Gradual blur is usually not an emergency but should be checked. Sudden blur or vision loss in one eye, especially with pain, distortion, or weakness elsewhere in the body, needs urgent medical attention.

Main Causes of Blurry Vision in One Eye

Common, non-urgent causes

• Refractive error: One eye may have developed more short-sightedness, long-sightedness or astigmatism than the other. This is called anisometropia.
• Cataract: Clouding of the natural lens rarely develops at exactly the same pace in both eyes. Glare, faded colours and haloes around lights are common.
• Dry eye or eye strain: An uneven tear film can make one eye blur on and off, especially during screen work.
• Contact lens problems: A dirty, damaged or misplaced lens can blur one eye.

Retina and macula conditions

• Age-related macular degeneration (AMD): Affects central vision. Straight lines may look wavy, and there may be a blank or grey patch.
• Diabetic retinopathy and macular oedema: Damage to tiny retinal blood vessels can cause swelling in the central retina.
• Central serous chorioretinopathy (CSC): Fluid collects under the retina, often in younger adults, sometimes linked to stress or steroid use.
• Epiretinal membrane: A thin scar-like layer on the retina that can blur or distort vision.

Serious causes that need urgent attention

• Retinal vein or artery occlusion: A blockage in the blood supply to the retina, usually causing sudden, painless vision loss.
• Optic neuritis: Inflammation of the optic nerve, often with pain on moving the eye and dull colour vision.
• Acute angle-closure glaucoma: A sudden rise in eye pressure with severe pain, redness, haloes and sometimes nausea.
• Corneal infection or ulcer: Blur with pain, redness and light sensitivity, especially in contact lens users.
• Stroke or transient ischaemic attack (TIA): Vision loss may come with facial drooping, slurred speech or weakness.

Symptoms to Watch For

• Hazy or foggy vision in one eye only
• Straight lines appearing bent or wavy
• A dark or empty spot in the centre of vision
• Colours looking washed out in one eye compared with the other
• Glare or haloes around lights at night
• Pain, redness or light sensitivity alongside the blur
• Blur that comes and goes, or that is worse at a certain time of day

When Is It Normal and When Should You Worry?

What Can You Do?

• Do a simple cover test: Cover each eye in turn and note how each one sees. Share this with your doctor.
• Check an Amsler grid (a square grid with a centre dot) if your doctor has given you one. New wavy lines are worth reporting.
• Rest your eyes during screen work: look 20 feet away for 20 seconds every 20 minutes.
• Remove contact lenses if your eye is blurry, red or painful, and don't put them back until it has been checked.
• Avoid self-medicating with steroid eye drops. They can raise eye pressure and worsen some infections.

These steps help you observe and protect your eye. They don't replace a proper eye examination.

When Should You See an Eye Doctor?

Book an appointment for any blur in one eye that lasts more than a few days or keeps coming back. Seek emergency care immediately for:

• Sudden vision loss or sudden blurry vision in one eye
• Severe eye pain with redness, haloes or nausea
• A shadow or curtain over part of your vision
• Pain when moving the eye with dim or dull colour vision
• Blur after an eye injury or chemical splash
• Vision changes with facial drooping, slurred speech or weakness on one side – go to the nearest emergency department, as this may be a stroke

An eye specialist at The Eye Foundation can help identify whether the blur is coming from the front of the eye, the retina or the optic nerve.

Diagnosis: What an Eye Doctor May Check

• Visual acuity and refraction: Measures each eye separately and checks whether glasses correct the blur.
• Slit-lamp examination: A microscope view of the cornea, lens and front of the eye, useful for cataract, dry eye and infection.
• Eye pressure measurement (tonometry): Checks for glaucoma.
• Dilated fundus examination: Allows a full view of the retina and optic nerve.
• OCT scan: Detects fluid, swelling or membranes in the macula.
• Pupil and colour vision tests: Help assess optic nerve function.
• Additional tests if needed: Fundus fluorescein angiography, visual field testing, or referral for blood tests or brain imaging.

Treatment

Treatment is chosen after the cause is identified. Your doctor will explain the options that apply to you.

• Refractive error: Updated glasses or contact lenses. Some people may later consider refractive surgery after a suitability assessment.
• Cataract: Glasses may help in early stages. Cataract surgery is considered when the blur affects daily activities.
• Dry eye: Lubricating drops, eyelid hygiene and screen habits; prescription treatment if needed.
• Macular and retinal conditions: May include eye injections (anti-VEGF), laser, or careful monitoring, depending on the condition.
• Urgent conditions: Angle-closure glaucoma, optic neuritis, corneal ulcers and vascular blockages need prompt treatment, often the same day, sometimes alongside other specialists.

Prevention and Eye-Care Tips

• Get a comprehensive eye check every one to two years, or as advised
• Test each eye separately now and then rather than relying on both together
• Keep blood sugar, blood pressure and cholesterol in check
• Don't smoke; it's linked to cataract and macular degeneration
• Wear UV-protective sunglasses outdoors
• Follow contact lens hygiene and replacement schedules strictly

Blurry vision in one eye is easy to overlook because the other eye fills in the gaps. Many causes are simple and very treatable, but some need prompt care to protect vision. Checking each eye separately and acting quickly on sudden changes are the two habits that matter most. If you've noticed a difference between your eyes, a comprehensive examination at The Eye Foundation can help pinpoint the reason.

Frequently Asked Questions

1. Why is one eye blurry and the other is not?

Each eye can develop changes at its own pace. A difference in glasses power, a cataract or a retinal problem can affect one eye first. An eye exam is the only way to find out which.

2. Is sudden blurry vision in one eye an emergency?

Yes, it should be treated as urgent. Sudden blur may be due to a blood vessel blockage, optic nerve inflammation, or high eye pressure, all of which need prompt care.

3. Can stress cause blurry vision in one eye?

Stress can contribute to eye strain and dry eye. It's also linked to central serous chorioretinopathy. Persistent blur should not be assumed to be stress-related without an examination.

4. Why is one eye blurry in the morning?

Mild morning blur often comes from dryness or mucus overnight and clears with blinking. Blur that lasts longer, or is always in the same eye, should be checked.

5. Can high blood sugar cause blurry vision in one eye?

Fluctuating blood sugar can temporarily change focus. Long-term diabetes can damage the retina, sometimes more in one eye. People with diabetes need yearly retinal check-ups.

6. Will glasses fix blurry vision in one eye?

Only if the cause is refractive. If glasses don't fully clear the vision, your doctor will look for other causes such as cataract or retinal changes.