10 causes for blurry vision in one eye - Insider

• Blurred vision in one eye can be due to a number of things including stroke or macular degeneration.
• There are plenty of infections that may also be the cause like COVID-19, iritis, or ocular herpes.
• Treatment varies widely depending on the underlying cause so proper diagnosis is important.
• Visit Insider's Health Reference library for more advice.

Blurry vision in one eye can affect all or just parts of your visual field. It makes objects appear out of focus or cloudy and can interfere with day to day activities, even with your glasses or contact lenses in place.

Sudden blurry vision in one or both eyes may indicate a medical emergency like a stroke or detached retina. Other, more gradual changes can be a sign of refractive errors.

Usually, your best option whenever you experience blurred vision in one eye is to get it checked by a doctor, says Farzan Gorgani, MD, an ophthalmologist at New Jersey Eye Center. An eye doctor (optometrist or ophthalmologist) can diagnose you and select the best treatment method.

Here are ten possible reasons why you're experiencing blurred vision in one eye and how to treat them.

5 causes that need immediate attention

If you have sudden blurry vision accompanied by pain, light sensitivity, dizziness, or worsening headache it is a good idea to go to the ER — these can be signs of one of the following medical emergencies.

1. Stroke

When areas of the brain responsible for visual processing are damaged in a stroke your vision will be affected. In fact, sudden blurry vision and changes in eyesight can be a key sign of a stroke. Other signs include:

• Severe headache
• Confusion or trouble speaking or understanding speech
• Balance or walking issues
• Numbness in arms, legs, or face, especially if one-sided

If you or someone close to you exhibits these signs seek medical help immediately. 

How to treat it: Strokes are treated by restoring blood flow to the brain or controlling bleeding — and the sooner treatment begins the better outcomes are.

Important: Sudden vision change or vision that dims or blacks out that lasts from a few minutes to an hour, and sometimes up to 24 hours, may be a sign of a transient ischemic attack — also called a mini-stroke — and needs medical attention as it can be a precursor to a stroke.

2. Detached retina

A detached retina is when your retina is pulled away from the back of the eye. Gorgani says the cause is usually age-related, due to injury, or genetic predisposition.

If your retina is detached or torn you won't feel pain in the eye but your vision will be suddenly blurred and you might also experience:

• Flashes of light
• Decreased peripheral vision
• Floaters (small black or gray shapes that move across your vision)
• Appearance of a shadow or curtain over your field of vision

How to treat it: A detached retina can lead to permanent vision loss, so it is important to quickly seek medical care as it usually requires surgical repair.

3. Brain tumor

Brain tumors can cause gradual blurred vision by putting pressure on parts of the brain that process eyesight. Depending on the size and location of the tumor, it could cause blurry vision in one or both eyes.

Note: In 2021, there were about 84,000 diagnosed brain tumors in the United States. It is estimated that 700,000 people are living with brain tumors and 71% of these tumors are benign.

In addition to vision changes, possible signs of brain tumor include:

• Headaches
• Difficulty concentrating or speaking
• Weakness in one side of the body
• Problems with coordination and balance
• Confusion or memory loss

How to treat it: Whether benign or malignant, brain tumors most often need to be surgically removed to prevent further irritation or potential damage to the brain. After surgery, a doctor may recommend radiation and chemotherapy to destroy any harmful cells the surgeons couldn't reach and also to prevent new cancerous cells from growing.

4. Closed-angle glaucoma

Closed-angle glaucoma is less common than the slowly progressing type of glaucoma, open-angle, and is an acute, medical emergency.

Gorgani says it happens when fluid drainage is blocked in the eye causing pressure to build up. The elevated pressure can cause permanent damage to the optic nerve and partial loss of vision or blindness in a matter of days to weeks.

Symptoms of closed-angle glaucoma will come on suddenly, will be only in one eye 90% of the time, and can include:

• Blurred vision with headache
• Severe one-sided eye pain  
• Seeing rainbow colored halos around lights
• Nausea and vomiting

How to treat it: Seek medical care immediately — a doctor can quickly reduce the pressure with medicated eye drops. After eye drops stabilize the condition, laser surgery helps further reduce eye pressure and prevent recurrence. 

5. Macular degeneration

Macular degeneration, also called age-related macular degeneration, or AMD, is the leading cause of vision loss in the United States, with up to 11 million people having a form of it.

AMD can cause various changes to your vision including: 

• Blurry vision in one or both eyes 
• Seeing dark spots or waves in the center of your vision
• Distortion of central vision, most noticeable while reading 
• Loss of ability to see fine details

AMD only affects the central part of your vision so it doesn't cause total blindness but can make it difficult to read, drive, or recognize faces.

There are two types of macular degeneration:

• Dry macular degeneration is when the macula, the part of your retina responsible for central vision, thins, causing gradual vision loss. It accounts for 90% of AMD cases.
• Wet macular degeneration is when blood vessels in the eye leak fluid. It tends to appear suddenly and worsen quickly, so it needs prompt medical attention.

What you can do: There is no cure for AMD. Treatment is geared towards managing  symptoms and slowing the progression of vision loss. The most common treatment is is medical injections  to the eye to reduce blood vessel growth and fluid leakage.

5 other causes of blurry vision in one eye

Some causes of blurry vision, though still needing medical attention, have a less urgent time frame for treatment than those listed above. Here are five of them:

6. Conjunctivitis

Conjunctivitis is an inflammation of the conjunctiva — the layer of tissue that lines the inner surface of the eyelid and covers the white part of the eye, says Robert Layman, OD, president of the American Optometric Association. Conjunctivitis can cause blurry vision but mild cases don't often affect vision. 

Other symptoms include:

• A gritty feeling in the eye
• Itching or burning of the eye
• Redness to the white of the eye 
• Excessive tearing or discharge from the eye
• Swollen eyelids

How to treat it: Conjunctivitis can have numerous causes. Check with your eye doctor first, but most mild cases of conjunctivitis will go away on their own and can be treated at home with cold compresses or eye drops. 

However, if you have pain, blurry vision, wear contact lenses, or your symptoms don't improve after a few days of at-home treatment, check in with your doctor. They may prescribe antibiotics, antivirals, or antihistamines depending on the cause of your conjunctivitis.

7. Other infections

Viruses, bacteria, and fungi can cause eye infections leading to blurry vision. Here are some common infections to keep in mind:

• Covid-19 is a viral infection that can cause blurred vision. This is usually due to conjunctivitis associated with Covid  — which may occur in up to 5% of cases and can cause blurred vision if severe.
• Endophthalmitis  is caused by bacteria or fungi in the eye, most commonly after eye surgery, injury, or a corneal infection.
• Keratitis can be caused by viruses, bacteria, or fungi. One type of keratitis is contact lense keratitis, which is caused by improper use of contact lenses, poor cleaning of lenses or the case, use of tap water, or poor fitting lenses. 
• Optic neuritis, the exact cause is unknown but it is associated with autoimmune diseases as well as bacteria and viruses.
• Ocular herpes is caused by the same virus responsible for cold sores and genital herpes — herpes simplex virus.
• Uveitis has many causes, the most frequent are infection, injury, and inflammatory disease.

8. Diabetes 

Diabetes can cause a serious eye condition called diabetic retinopathy which affects about 29% of people with diabetes over the age of 40. Retinopathy most often happens in both eyes, but it can occur in just one, and is painless. 

"Over time, diabetes may damage small blood vessels through the body, including in the retina. Diabetic retinopathy occurs when these tiny vessels leak blood and other fluids. This causes the retinal tissue to swell, resulting in cloudy or blurred vision," says Layman. 

Note: Blurry vision can be caused by high blood sugar, even if you aren't diagnosed with diabetes, and it can also be a symptom of prediabetes. 

How to treat it: Blood sugar control can help slow the progression of diabetic retinopathy. More advanced cases are treated with medication, laser treatment, and surgery.

9. Migraine         

A type of migraine, known as a retinal migraine, causes visual changes like blurred spots, twinkling lights, and temporary blindness in just one eye.

These visual changes can come on before, during, or after a headache.

Retinal migraines usually last less than an hour, but can mimic other serious conditions like giant cell arteritis and carotid artery disease, so it is important to consult a doctor if you are experiencing symptoms.

Layman says retinal migraines are:

• More common in women than men
• Most common from age 30-39
• More common if you have a family history of migraines

How to treat it: Retinal migraines are treated similarly to other migraines with NSAIDS for pain and anti-nausea medication. If over the counter medications don't work, your doctor may prescribe preventative medications like beta blockers or anti-epileptics.

10. Cataract

Cataracts cause the lens of the eye to get cloudy and blur your vision. Cataracts usually develop in both eyes, but the clouding of the lens can happen at different rates, affecting one eye more than the other.

They are fairly common and your risk of developing cataracts increases from age 40 onward — 

as everyone's natural lens will develop a cataract as we age. Genetics, certain medications, and other medical conditions can cause cataracts to grow quicker. 

How to treat it: Eyeglass prescriptions help with visual loss from cataracts, but if it advances far enough, surgery is an option to help restore your vision.

Insider's takeaway

Blurry vision in one eye is a fairly common symptom with a wide range of causes from mild to severe. 

In some cases, blurry vision will be transient and treatable. However, if you experience sudden blurry vision it might be a sign of a serious medical condition that needs immediate attention. 

Even if you do not use glasses or contacts, annual eye exams are recommended to complete a full health assessment of the eyes and check for systemic conditions affecting the eyes.  

Adam Barnes