Slowly progressive blurred vision is usually caused by long-term medical conditions. Sudden blurring is most often caused by a single event.
Here are 17 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.
When it happens, you see flashing lights and black flecks followed by an area of blurred or absent vision. Without emergency treatment, vision in that area may be permanently lost.
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, such as weakness on one side of your body or the inability to speak.
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.
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 treatments with eyedrops to open the angle, decrease the pressure, and decrease the inflammation. Many times a laser procedure, called laser iridotomy, is also required.
6. Eye strain
Eye strain 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 eye strain. Other causes include reading and driving, especially at night and in poor weather.
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.
8. 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.
9. High blood sugar
Very high blood sugar levels cause the lens of your eye to swell, which results in blurred vision.
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.
The iris is the colored part of your eye. Iritis occurs when an autoimmune reaction or an infection causes the iris to become inflamed.
It can be painful and cause sensitivity to light, also called photophobia.
Inflammation of the cornea is called keratitis. It’s usually caused by an infection. Using one pair of contacts for too long or reusing dirty contacts increases your risk for this.
13. Macular hole
The macula is the center of your retina that is responsible for your central vision. It can develop a tear or break that causes blurry vision. It usually only affects one eye.
14. 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.
15. Optic neuritis
The optic nerve connects your eye and your brain. Inflammation of the optic nerve is called optic neuritis.
16. Temporal arteritis
Inflammation in the medium sized arteries is called temporal 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.
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.
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 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 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.
- 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. The symptoms resolve within 24 hours on their own. You may be given blood thinners to reduce 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.
- Eye strain. If you have eye strain, take a break and rest your eyes. One thing you can do to prevent it is follow the 20-20-20 rule. To do this, focus on something 20 feet away for 20 seconds every 20 minutes when you’re looking at a screen or one thing for a long time.
- Conjunctivitis. This usually goes away on its own, but antibiotics or antiviral medication can often speed recovery and lower the chance it will spread.
- 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.
- Iritis. This usually heals completely on its own or with steroids. However, it commonly reoccurs. If it becomes chronic and resistant to treatment, you can lose your vision and immune modulating medicines may be required to prevent this.
- 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.
- Macular hole. If it doesn’t heal on its own, surgical repair of the hole is usually done.
- 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.
- Uveitis. Like iritis, it resolves spontaneously or with steroids. Repeated recurrence can lead to treatment resistance and, potentially, blindness.
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. You should see 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.