Sudden Blurry Vision in One Eye: Causes and When It's an Emergency

You cover one eye by chance and realise the other one isn't seeing clearly. Or you wake up and everything looks hazy on one side, even after you rub your eyes and blink a few times.

Will it clear up on its own? Sometimes it does. Blurring in one eye can come from something as simple as a dry eye or a glasses power that's out of date. But sudden blurry vision in one eye can also be the first sign of a condition where every hour counts. This guide will help you tell the difference and know when to stop waiting and get to an eye hospital.

Why Only One Eye?

When both eyes blur together, the cause is usually something general, like tiredness, dry air or a change in blood sugar. When only one eye is affected, the problem is more likely to be in that eye itself: its cornea, lens, retina or optic nerve.

Here's the tricky part. Your good eye quietly makes up for the weaker one, so many people don't notice one-sided blurring for a while. That's why it's so often found by accident.

Emergency Causes: Get Seen the Same Day

If sudden blurry vision in one eye comes with any of the signs below, treat it as urgent. Getting treatment within hours can make the difference between saving and losing sight.

Retinal detachment. The retina, the light-sensitive layer at the back of the eye, pulls away from where it should be. Watch for a sudden shower of floaters, flashes of light, or a dark curtain or shadow moving across part of your vision.

Retinal vein or artery occlusion. A blood vessel in the retina gets blocked, a bit like a stroke in the eye. An artery blockage usually causes sudden, painless and severe loss of vision. People with high blood pressure, diabetes or heart disease are at higher risk.

Stroke or mini-stroke (TIA). Sudden blurring or loss of vision can be a sign of a stroke, especially if it comes with a drooping face, weakness or numbness on one side of the body, slurred speech or confusion. This is a medical emergency. Call an ambulance or go to the nearest emergency department straight away.

Acute angle-closure glaucoma. The pressure inside the eye rises very quickly. It usually causes a red, painful eye, blurred vision, halos around lights and a headache, and sometimes nausea or vomiting.

Optic neuritis. This is inflammation of the optic nerve, and it's more common in young adults. Vision in one eye blurs or dims over a day or two, the eye hurts when you move it, and colours can look washed out.

Bleeding inside the eye. In people with diabetes, fragile new blood vessels on the retina can bleed into the gel inside the eye. This causes sudden blurring, dark spots or shadows that look like cobwebs.

Less Urgent Causes, but Still Worth Checking

Not every blurry eye is an emergency. The causes below are common and usually treatable, but you should still see a doctor within a few days:

• Refractive error: your eye power has changed, or one eye has a power that was never corrected
• Dry eye: blurring that gets better when you blink, often worse after screen use or time in AC
• Cataract: slow clouding of the lens. It usually develops gradually, but people sometimes notice it all at once
• Eye infection or corneal ulcer: often comes with redness, pain, discharge or sensitivity to light
• Migraine aura: shimmering or zig-zag patterns that usually pass within an hour
• Macular problems: straight lines look wavy, or there's a blurry patch in the centre of your vision

Sudden Blurry Vision in One Eye After Waking Up

A lot of people first notice blurring in the morning. Often it's just because the eye dried out overnight, especially if you sleep under a fan or AC, or if your eyelids don't close fully while you sleep. This kind of blur usually clears after a few minutes of blinking.

If it doesn't clear once you've been up for a while, or it seems worse than usual, get it checked. Some retina and nerve problems are first noticed on waking simply because that's the first time you properly look around.

Left Eye Blurry, Right Eye Fine: What Does It Mean?

No condition specifically targets the left or right eye. The same causes apply to either side. What matters is how quickly the blur started, whether it's getting worse, and whether you have other symptoms like pain, flashes, floaters, redness or a shadow in your vision.

Can Blurred Vision Go Back to Normal?

Often, yes. Blurring from dry eye, a power change or an infection usually clears completely with the right treatment. Blur from a cataract can be fixed with surgery. Even when sudden blurry vision in one eye comes from something serious like a retinal detachment, early treatment gives you the best chance of getting useful vision back.

The key word is early. Waiting a few days to "see if it gets better" is the most common reason people lose vision that could have been saved.

What Will the Eye Doctor Check?

Your eye specialist will usually test the vision in each eye, check your eye pressure, and put in drops to widen your pupils so they can see the retina and optic nerve clearly. Depending on what they find, you may need a scan such as an OCT, which takes a detailed picture of the retina. If they suspect the cause is in the brain or nerves, they may refer you for brain imaging. Most of these tests are quick and painless.

Seek Help Immediately If You Notice

• Sudden loss of vision, even if it comes back
• A curtain or shadow over part of your vision
• A sudden burst of new floaters or flashes of light
• A painful red eye with blurred vision or halos around lights
• Blurring along with a drooping face, arm weakness or trouble speaking

Expert Retina and Neuro-Eye Care at The Eye Foundation

Sudden changes in vision need a fast, accurate diagnosis. The retina and neuro-ophthalmology specialists at The Eye Foundation are equipped to assess and treat urgent eye conditions, from retinal detachment to optic nerve problems. If you've noticed sudden blurry vision in one eye, don't wait for it to settle. Visit your nearest Eye Foundation hospital today.

Frequently Asked Questions

Is sudden blurry vision in one eye always serious?

No, but it should always be checked. Some causes are harmless, while others, like a retinal detachment or a blocked blood vessel, need treatment within hours.

Can high blood sugar cause blurry vision in one eye?

Changes in blood sugar more often blur both eyes. But diabetes can also cause bleeding or swelling in the retina of one eye, so if you have diabetes, get any new blurring checked promptly.

Should I go to an eye hospital or a general emergency room?

If you have signs of a stroke, like weakness, a drooping face or slurred speech, go to the emergency department immediately. If you have sudden blurring, flashes, floaters or a shadow without those signs, see an eye specialist the same day.