What causes blurry vision in one eye?

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In many cases, blurry vision is not a sign of a life threatening condition. However, sudden vision changes can sometimes mean a person needs emergency treatment. Being aware of the signs of these conditions can help with deciding when to seek help.

Anyone who experiences blurry vision along with any of the following symptoms should seek immediate help, as it can indicate a medical emergency:

• a sudden, severe headache
• a headache following a knock to the head
• difficulty staying awake
• loss of consciousness
• drooping or numbness on one side of the face
• inability to raise one or both arms
• slurred speech

People should also seek help right away if they experience the following symptoms, which can indicate retinal detachment:

• sudden vision changes, such as flashes of light
• many more eye floaters than usual
• vision that resembles a curtain being pulled over the eyes

Read on to find out about some of the more common causes of blurry vision in one eye.

The Centers for Disease Control and Prevention (CDC) states that refractive errors are the most common cause of eye problems in the United States. Refractive errors include:

• nearsightedness, or myopia
• farsightedness, or hyperopia
• astigmatism, or distorted vision at all distances
• presbyopia, or difficulty seeing objects up close

The most common symptom of a refractive error is blurry vision, but it can also cause:

• hazy vision
• double vision
• seeing halos around bright lights
• eyestrain
• headaches

Eyeglasses or contact lenses can help people with refractive errors see more clearly. However, some people may choose to have surgery.

Bacteria, fungi, and viruses can all cause an eye infection, which can affect one or both eyes. Potential symptoms of an eye infection include:

• red or bloodshot eyes
• itchiness
• swelling
• pain
• discharge or crust around the eyes
• vision problems, including blurry vision

Conjunctivitis, or pinkeye, is a common type of eye infection. Other types, such as cellulitis, can be severe if a person does not receive treatment.

If a person has the symptoms of an eye infection, they should seek medical care. Depending on the cause, treatment could involve eye drops, topical medications, or oral antibiotics.

Treatment can also consist of supportive therapy, such as cold compresses, and monitoring.

Migraine is a condition that causes moderate to severe headaches. Some people also experience auras, which are sensory disturbances that occur before or during a headache.

Aura symptoms can include:

• blurry vision
• short-term vision loss
• seeing shapes or zig-zag lines
• tingling
• weakness
• difficulty speaking

According to the American Migraine Foundation, these symptoms will usually last 5–60 minutes for those who experience aura. People can also have silent migraine, a migraine with aura but no pain.

Migraine treatment may involve pain relievers. Over-the-counter medications may be sufficient for those with an occasional migraine. However, people with frequent episodes may require prescription options, such as triptans, to manage the condition.

Learn more about managing migraine at home here.

Cataracts develop when the lens of the eye clouds over, causing blurry vision. This can happen in one or both eyes. Cataracts tend to be age-related and are common in older adults.

The symptoms of cataracts can come on over time. They include:

• blurry vision
• hazy vision
• less colorful vision
• difficulty seeing at night
• difficulty reading
• seeing double
• seeing a halo around lights

The only way to treat cataracts is through surgery. During the operation, a surgeon will replace the clouded lens with an artificial one.

Age-related macular degeneration (AMD) affects the macula, which is the part of the eye that enables people to see fine details. The condition can start in one eye and progress to the other, causing a loss of sharp or central vision.

There are two types of AMD:

Wet AMD

Wet AMD occurs when blood vessels form behind the retina and under the macula. These bleed and leak into the eye, scarring and damaging it.

Straight lines appearing wavy is an early symptom of wet AMD.

Dry AMD

As people get older, the macula gets thinner, leading to blurry vision. This is the most common form of AMD, accounting for 70–90% of cases. Drusen, or tiny yellow or white deposits under the retina, is the most common early sign of dry AMD.

There is no cure for either type of AMD. However, there are things people can do to slow its progression, including:

• stopping smoking
• eating a balanced diet
• exercising regularly
• maintaining healthy blood pressure and cholesterol levels

In people with wet AMD, doctors may also recommend anti-vascular endothelial growth factor drugs or laser treatment.

For people with diabetes, blurry vision may be a sign of diabetic eye disease. This occurs when high blood glucose levels damage the blood vessels in the eye, causing conditions such as:

• diabetic retinopathy
• diabetic macular edema
• cataracts
• glaucoma

There are often no early symptoms of diabetic eye disease, but a person may experience:

• blurry vision
• vision that changes from day to day
• areas of darkness or vision loss
• a loss of color vision
• dark strings or floaters
• flashes of light

Reducing the risk

It is important for people with diabetes to get annual dilated eye exams, as these can help doctors detect early signs of damage.

People can lower the risk of these complications by managing their blood glucose levels, blood pressure, and cholesterol levels.

Treatment for existing diabetic eye disease may involve medications, laser procedures, surgery, or a combination of all three.

Sometimes, blurry vision is a sign of a stroke. A stroke happens when something stops blood from reaching part of the brain. This might be a blood vessel blockage or rupture.

People can remember the symptoms of a stroke by acting F.A.S.T. This acronym stands for:

• face drooping
• arm weakness
• speech difficulty
• time to call 911

Sudden trouble seeing or walking or a severe headache can also be symptoms of stroke. Treatment may include medications to break up blood clots, procedures to repair blood vessels or surgery.

If someone has these symptoms, do not hesitate to call for an ambulance. Paramedics can begin treatment on the way to the hospital.

Some people with COVID-19 experience conjunctivitis, which can cause blurry vision, red or watery eyes, and a sensation that a foreign object is in the eye.

Although the risk of serious complications from COVID-19 is lower, the CDC recommends that people stay up to date with vaccinations, take steps to reduce the spread of the condition, and follow local advice if they catch COVID-19.

Other symptoms of COVID-19 include:

• fever or chills
• cough
• shortness of breath or difficulty breathing
• fatigue
• muscle or body aches
• headache
• loss of taste or smell
• sore throat
• stuffy or runny nose
• feeling or being sick
• diarrhea

Anyone who suspects they have COVID-19 can order free tests to take at home, buy home tests at pharmacies or online, or travel to a testing location.

Several things can cause blurry vision in one eye. Refractive errors are a common cause, as are age-related conditions, such as cataracts and AMD. Some people with migraine may experience blurry vision if they get aura or silent migraine.

A doctor can diagnose the cause of blurry vision and recommend the best options for treatment. However, if a person may have conjunctivitis as a result of COVID-19, people should take a test and follow local advice to reduce the spread.

People with sudden vision changes or loss should seek immediate medical help, particularly if they also have underlying conditions, such as diabetes.