Blurry vision is very common. A problem with any of the components of your eye, such as the cornea, retina, or optic nerve, can cause sudden blurred vision.

Slowly progressing blurred vision is usually caused by long-term medical conditions. Sudden blurring is most often caused by a single event.

Here are 18 causes of sudden blurred vision.

Some causes of sudden blurry vision are medical emergencies that must be treated as soon as possible to prevent permanent damage and vision loss.

1. Detached retina

A detached retina occurs when your retina tears away from the back of your eye and loses its blood and nerve supply. According to the National Eye Institute, this is usually the result of aging or injury, but it can also be a complication of diabetes.

When it happens, you see flashing lights or floaters, which are sometimes dark or black. You may also experience an area of blurred or absent vision, sometimes described as a curtain coming down over the vision. Without emergency treatment, vision in that area may be permanently lost.

2. Stroke

Blurry or lost vision in both eyes can occur when you have a stroke affecting the part of your brain that controls vision. A stroke involving your eye causes blurred or lost vision in only one eye.

You may have other symptoms of a stroke, including:

  • face drooping
  • weakness in the arms
  • difficulty speaking
  • sudden numbness
  • sudden confusion
  • dizziness or a loss of balance and coordination
  • severe headache with no known cause

3. Transient ischemic attack

A transient ischemic attack (TIA) is a stroke that lasts less than 24 hours. One of its symptoms can be blurred vision in one or both eyes.

4. Wet macular degeneration

The center of your retina is called the macula. Abnormal vessels may grow, causing blood and other fluid to leak into the macula. This is called wet macular degeneration.

It causes blurriness and vision loss in the center part of your visual field. Unlike dry macular degeneration, this type can begin suddenly and progress rapidly.

While dry macular degeneration proceeds slowly, it can quickly progress to wet and cause sudden symptoms.

5. Angle closure glaucoma

Angle closure glaucoma occurs when the drainage system within the eye is blocked. In this situation, the pressure inside the eye can go up very quickly, causing redness, pain, and nausea.

This is a medical emergency and requires treatment with eye drops to open the angle, decrease the pressure, and decrease the inflammation.

6. Endophthalmitis

An infection in the fluids of your eyeball can cause severe inflammation. This condition is called edophthalmitis and is a serious medical emergency. In addition to blurry vision, you may experience pus discharge from the eyes and swollen or puffy eyelids.

The infection often occurs as a result of surgery. It may also be the result of an infection in another part of the body that has spread to the eye.

7. Concussion

A concussion is a mild traumatic brain injury. A majority of the brain’s pathways are dedicated to vision and controlling the eye, so it’s not surprising that brain injuries can result in blurry vision.

Permanent damage or vision loss are unlikely with a concussion. However, spinal injuries or a subdural hematoma may accompany a concussion, so it’s important to have a doctor examine you as soon as possible.

8. Conjunctivitis

Also called pink eye, conjunctivitis is an infection of the outside lining of your eye. It’s usually caused by a virus but can also be caused by bacteria or allergies.

9. Keratitis

Inflammation of the cornea is called keratitis. It’s usually caused by an infection. Using one pair of contacts for too long, reusing dirty contacts, or sleeping in contacts increases your risk of this.

10. Uveitis

The uvea is a collection of pigmented structures in the eye, including the iris. An infection or autoimmune reaction can cause it to become inflamed and painful, which is called uveitis. The most common form of uveitis is iritis, which is an inflammation of the iris.

Uveitis can occur by itself or as part of an autoimmune condition, such as rheumatoid arthritis or sarcoidosis. It can also be caused by infections like herpes.

It can be painful and cause sensitivity to light, also called photophobia.

11. Eyestrain

Eyestrain can occur after looking at and focusing on something for a long time without a break.

When it’s the result of focusing on an electronic device like a computer or cellphone, it’s sometimes called digital eyestrain. Other causes of eyestrain include reading and driving, especially at night and in poor weather.

12. Corneal abrasion

Your cornea is the clear covering on the front of your eye. When it gets scratched or injured, you may develop a corneal abrasion. In addition to blurry vision, you may feel like there’s something in your eye.

13. High blood sugar

Very high blood sugar levels cause the lens of your eye to swell, which results in blurred vision.

14. Hyphema

Dark red blood that pools inside the front of your eyeball is called a hyphema. It’s caused by bleeding that occurs after your eye is injured. It can become painful if it increases the pressure inside your eye.

15. Macular hole

The macula is the center of your retina that is responsible for your central vision. It can develop a hole that causes blurry vision. It usually only affects one eye.

16. Migraine with aura

Often migraine attacks are preceded by an aura, which can cause blurred vision. You may also see wavy lines or flashing lights and have other sensory disturbances. Sometimes you may have an aura without head pain.

17. Optic neuritis

The optic nerve connects your eye and your brain. Inflammation of the optic nerve is called optic neuritis.

It’s usually caused by an autoimmune reaction or multiple sclerosis. Other causes are autoimmune conditions, such as lupus, or infections. Most often, it affects only one eye.

18. Temporal arteritis

Inflammation in the medium and large arteries is called temporal arteritis or giant cell arteritis. The vessels around your temples can be involved, causing a throbbing headache in your forehead, but it can also cause your vision to blur or disappear.

Along with sudden blurred vision, you might have other eye symptoms that can range from mild to serious, such as:

Some symptoms are more common with specific eye conditions, such as:

  • eye discharge, which can signal infection
  • headache and nausea, which are common with migraine
  • itchiness, which may indicate allergic conjunctivitis
  • speech difficulties or one-sided weakness, which can accompany stroke or TIA
When is it an emergency?

The following warning signs could mean you have a serious eye condition that can cause permanent eye damage and vision loss. If you have any of them, go to the emergency room (ER) immediately for evaluation and treatment.

  • sudden unexplained change in your vision
  • eye pain
  • eye injury
  • signs of a stroke, such as a facial droop, one-sided weakness, or difficulty speaking
  • significantly reduced vision, especially in only one eye
  • loss of one area of your vision, known as visual field defect
  • sudden blurred vision when your immune system is weak due to conditions like HIV or treatments like chemotherapy

Treatment will depend on the condition affecting your vision.

Conditions requiring immediate evaluation

  • Detached or torn retina. This requires emergency surgical repair to avoid irreversible vision loss.
  • Stroke. Prompt and appropriate treatment for the type of stroke you’re having is critical to prevent the death of your brain cells.
  • Transient ischemic attack. Although symptoms resolve within 24 hours on their own, a TIA is a serious warning sign for stroke. You may be given blood thinners to lower the risk of a stroke in the future.
  • Wet macular degeneration. Medications injected into the eye may help improve vision. Treatment with laser photocoagulation can slow vision loss but can’t restore your vision. Special vision-enhancing devices are sometimes used to help you see better.
  • Angle closure glaucoma. You will need several different medications, including topical and oral pressure-lowering drugs, and occasionally steroids to reduce the fluid in your eye. Many times, you may require a laser procedure called laser iridotomy.
  • Endophthalmitis. An ophthalmologist will inject antibiotics or an antifungal medication into your eye. They may also give you a steroid to reduce swelling.
  • Concussion. A concussion should be evaluated, but visual symptoms usually resolve in 7 to 10 days on their own. If problems with eye movement or focus persist, your doctor may recommend vision therapy.

Infections

  • Conjunctivitis. This usually goes away on its own, but antibiotics or antiviral medication can often speed recovery and lower the chance it will spread.
  • Keratitis. When caused by an infection, keratitis is treated with antibiotic drops. For a severe infection, oral antibiotics and steroid eye drops may be used.
  • Uveitis, including iritis. This usually requires steroid treatment. However, it commonly reoccurs. If it becomes chronic and resistant to treatment, you can lose your vision. Immune modulating medications may be required to prevent this.

Other causes

  • Eyestrain. If you have eyestrain from looking at a screen or one thing for a long time, take a break and rest your eyes. To prevent eyestrain, the American Optometric Association suggests you follow the 20-20-20 rule. To do this, focus on something 20 feet away for 20 seconds every 20 minutes.
  • Corneal abrasion. This typically heals on its own in a few days. Antibiotics can treat or prevent an infection.
  • High blood sugar. Lowering blood sugar solves the problem.
  • Hyphema. When there are no other injuries and your eye pressure isn’t increased, bed rest and an eye patch should help. If it’s more severe and the pressure is very high, your ophthalmologist may remove the blood surgically.
  • Macular hole. If it doesn’t heal on its own, the hole is usually repaired surgically.
  • Migraine with aura. An aura doesn’t need treatment, but it’s a signal that you should take your usual medication for your migraine.
  • Optic neuritis. This is managed by treating the underlying condition, but steroids may be helpful even if there are no systemic findings.
  • Temporal arteritis. This is treated with long-term steroids. Treatment is important to avoid permanent vision problems.

When treatment is delayed, some causes of sudden blurry vision can result in vision loss. However, prompt and appropriate treatment leads to a good outcome without complications for most causes of sudden blurry vision.

Many things can cause your vision to suddenly become blurred. Contact your doctor about any sudden unexplained change in your vision.

If you think you have a detached retina, wet macular degeneration, or are having a TIA or stroke, go to the ER for immediate treatment to have the best outcome.