# Why is my vision suddenly blurry? Causes and when it is urgent

> Vision that blurs suddenly, within seconds, minutes or hours, should be treated as urgent, especially if it affects one eye or comes with pain, flashes, a shadow in your sight, a severe headache or weakness. Go to an emergency unit. Blur that builds up slowly over weeks or months usually means you need glasses or have a cataract, and calls for an eye test.

Source: https://seebetter.co.za/blog/sudden-blurry-vision-causes/
Publisher: See Better (https://seebetter.co.za/)
Section: Eye conditions
Published: 2026-10-11
Last updated: 2026-10-11

## Key points

- Sudden blur is urgent. Gradual blur needs a routine eye test.
- Cover each eye in turn to find out whether one eye or both are affected.
- Stroke, retinal detachment and acute glaucoma can all start with blurred vision.
- Blur that clears when you blink is usually dry eye.

## First, two quick checks

**How fast did it happen?** Blur that arrives over seconds to hours is treated very differently from blur that has crept up over months.

**Is it one eye or both?** Cover one eye, then the other. People are often surprised to find that the problem is in one eye only. Sudden blur in one eye usually comes from the eye itself. Sudden blur in both eyes at once more often has a general cause, such as blood sugar, blood pressure, a migraine or a problem in the brain.

## When blurry vision is an emergency

> Go to an emergency unit or call 112 from a cellphone immediately if blurred vision comes on suddenly together with any of the following: a drooping face, weakness or numbness on one side, slurred speech or confusion; a severe headache; a painful red eye with nausea or halos around lights; a dark curtain or shadow across your vision; a sudden shower of floaters or flashes; double vision; or after an injury or a chemical splash.

These are the causes that cannot wait:

- **Stroke or mini-stroke (TIA).** There may be sudden loss or blurring of vision, often with weakness, numbness or trouble speaking. Even if it passes within minutes, it is an emergency.
- **Retinal detachment.** Flashes and floaters come first, then a shadow that spreads across the vision. It is painless. See [eye floaters and flashes](https://seebetter.co.za/blog/eye-floaters-and-flashes/).
- **Acute angle-closure glaucoma.** Severe eye pain, a red eye, halos and vomiting. See [glaucoma: symptoms and testing](https://seebetter.co.za/blog/glaucoma-symptoms-and-testing/).
- **A blocked blood vessel in the retina.** Sudden, painless loss of vision in one eye.
- **Bleeding inside the eye,** often in people with diabetes.
- **Wet macular degeneration.** Sudden distortion or a dark patch in the centre of vision.
- **Inflammation of the optic nerve.** Blur and washed-out colours in one eye, with pain when the eye moves.
- **Inflamed arteries in people over 50** (giant cell arteritis). Vision loss with a new headache, a tender scalp or jaw pain when chewing.
- **A corneal infection,** particularly in contact lens wearers. The eye is painful, red and sensitive to light.
- **In pregnancy:** blurred vision with a headache and swelling can be a sign of pre-eclampsia. Contact your clinic or hospital immediately.

Do not drive yourself. Time matters with all of these.

## Less urgent causes of sudden or on-and-off blur

- **Dry eye.** The blur comes and goes and clears for a moment after blinking. It is common during long sessions at a screen. See [dry eyes: causes and relief](https://seebetter.co.za/blog/dry-eyes-causes-and-relief/).
- **Migraine aura.** A shimmering or zigzag disturbance grows over 10 to 30 minutes in both eyes and then fades, often followed by a headache.
- **Blood sugar swings.** High sugar makes the lens swell and blurs vision for days or weeks. This can be the first sign of diabetes. See [diabetes and your eyes](https://seebetter.co.za/blog/diabetes-and-your-eyes/).
- **Low blood pressure or standing up quickly.** Vision dims for a few seconds.
- **Eye strain.** Blur after hours of close work that recovers with rest.
- **New medication.** Some medicines affect focusing. Read the leaflet and ask your pharmacist.
- **Pink eye or an allergy.** Watering and discharge blur vision until you blink.

None of these is an emergency, but all of them deserve attention if they keep happening. Blur that recurs or does not fully clear should be checked within days.

## Blur that comes on gradually

If your vision has become blurrier over months, the likely causes are much more ordinary:

- a new or changed prescription: [short-sightedness, long-sightedness](https://seebetter.co.za/blog/short-sighted-vs-long-sighted/) or [astigmatism](https://seebetter.co.za/blog/what-is-astigmatism/)
- [presbyopia](https://seebetter.co.za/blog/presbyopia-blurry-near-vision-after-40/), if you are over 40 and the blur is up close
- a [cataract](https://seebetter.co.za/blog/cataract-symptoms/), if you are older and bothered by glare
- early eye disease that needs to be picked up

This is what a routine eye test is for. It measures what has changed and checks the health of your eyes at the same visit.

## What to do now

1. **Sudden blur with any warning sign above:** go to an emergency unit now.
2. **Sudden blur in one eye, even without pain:** see a doctor or an ophthalmologist the same day.
3. **Blur that comes and goes:** make a note of when it happens and book an eye test this week. See a doctor if you also feel very thirsty, tired or unwell.
4. **Blur that has built up slowly:** book a routine eye test.

A mobile eye test is the right choice for the last two, and not for emergencies. See Better tests eyes at home in Gauteng for R450.

## Frequently asked questions

### Can stress or tiredness cause blurry vision?

Tiredness and long hours of focusing can cause temporary blur and eye strain that recover with rest. Stress alone does not usually blur vision. Blur that is sudden, lasts or affects one eye should not be put down to stress without an examination.

### Why is my vision blurry in one eye only?

It can be something simple, such as dryness or a different prescription in that eye, or something that needs urgent treatment, such as a retinal or optic nerve problem. If it came on suddenly, have it examined the same day.

### Can high blood pressure cause blurred vision?

Very high blood pressure can damage the blood vessels in the retina and blur vision, sometimes with a headache. Sudden blur with a severe headache needs emergency care.

### Why is my vision blurry in the morning?

Dry eyes are the usual reason, because the eyes dry out during sleep, especially under a fan or air conditioning. It should clear after blinking or using lubricating drops. If it lasts for hours, have your eyes checked.

## About See Better

See Better is a mobile optometry practice in Gauteng, South Africa. A qualified, HPCSA-registered optometrist travels to the client's home, workplace, school or event, so there is no practice to visit.

- Areas served: Johannesburg, Pretoria (Tshwane), Ekurhuleni (East Rand), the West Rand and the Vaal.
- Eye test at home: R450 (cash price).
- Eye test + frame + single vision lenses + tint: R1199 (cash price).
- Eye test + frame + bifocal lenses + tint: R1699 (cash price).
- Eye test + frame + multifocal lenses + tint: R2099 (cash price).
- All glasses carry a 1-year warranty.
- We are registered with most medical aids and charge at medical aid tariffs.
- Book on WhatsApp: +27 66 181 8667 (https://wa.me/27661818667)
- Email: info@seebetter.co.za
- Website: https://seebetter.co.za/