What could be causing your blurry vision?

Blurry vision may be temporary or long-lasting and can affect one or both eyes. While some causes of blurry vision are minor and easily treated, others may signal a more serious condition that requires medical attention. Understanding the potential causes can help you determine when to seek care and how to protect your vision.

What is blurry vision?

Blurry vision means your eyesight is not as sharp or clear as usual. Objects may appear hazy, out of focus, or distorted. Blurry vision can develop gradually over time or come on suddenly. It may be caused by issues with the eye itself or by underlying health conditions affecting vision.

Common causes of blurry vision

Several common conditions can lead to blurry vision. These are often treatable with corrective lenses, lifestyle changes, or medications.

Refractive errors

According to Dr. Joan Miller, professor of ophthalmology at Harvard Medical School, "The most common cause of blurry vision is refractive error."

The eye typically produces a sharp image by bending (refracting) light to focus it on the retina. Refractive errors happen when part of the eye's optical system does not properly direct light, leading to a blurred image. The most common refractive errors include:

• Myopia (nearsightedness) occurs when the eye is too long or its focusing power is too strong. This causes light to focus in front of the retina instead of directly on it, making distant objects look blurry.
• Hyperopia (farsightedness) occurs when the eye is too short or doesn’t have enough focusing power. This causes light to focus behind the retina instead of directly on it, making nearby objects appear blurry.
• Astigmatism: caused by an unevenly shaped cornea, which makes light focus unevenly on the eye. This leads to blurry vision at all distances.
• Presbyopia: also called "aging sight," presbyopia makes it harder to focus on close objects. It happens gradually with age as the lens loses its ability to adjust, making tasks like reading more difficult.

Refractive errors can be corrected with glasses, contact lenses, or laser eye surgery. If left uncorrected, these conditions can contribute to eye strain, headaches, and difficulty performing daily tasks.

Dry eye

Dry eye occurs when your eyes do not produce enough tears or when tears evaporate too quickly. This can lead to irritation, redness, and blurred vision. Causes of dry eye include:

• aging
• hormonal changes
• eye surgery
• certain medications such as antihistamines and antidepressants
• prolonged screen time
• environmental factors like wind, smoke, or dry air
• autoimmune conditions, such as Sjögren’s syndrome
• other systemic diseases such as diabetes and Parkinson’s disease.

Using artificial tears, taking breaks from screens, and using a humidifier can help relieve symptoms. In some cases, prescription eye drops or procedures to block tear drainage may be needed.

Eye strain

Spending long hours reading, using digital screens, or focusing on a task without breaks can strain your eyes and cause temporary blurry vision. Other symptoms may include dry eyes, headaches, and difficulty focusing.

To prevent eye strain, follow the “20-20-20 rule:” every 20 minutes, look at something 20 feet away for at least 20 seconds. Proper lighting, adjusting screen brightness, and using blue light–filtering glasses may also help reduce symptoms.

Medication side effects

Blurry vision can be a side effect of different medications. If you notice vision changes after starting a medication, talk to your doctor. They may adjust your dosage or recommend a different drug.

Other causes of blurry vision: Eye diseases and conditions

Certain eye diseases and conditions can also lead to blurry vision. These often develop over time and may require medical intervention to prevent permanent vision loss.

“Regular eye exams are vital for detecting treatable eye diseases before symptoms appear,” says Dr. Miller. The American Academy of Ophthalmology recommends exams every two to four years starting at age 40, increasing in frequency with age. Higher-risk individuals may need more frequent eye exams.

Cataracts

Cataracts are cloudy areas in the lens of the eye. They can lead to blurry or distorted vision, difficulty seeing at night, and increased sensitivity to light.

Dr. Miller explains, “People who develop cataracts will notice blurry vision, usually developing gradually and affecting their ability to see at distance and near. They may also complain of difficulties seeing on sunny days or see halos from oncoming headlights.”

Cataracts are most common as people get older and are often considered a normal part of aging. However, certain factors can make them develop more quickly, including:

• smoking
• alcohol consumption
• poor nutrition
• medical conditions such as diabetes and HIV/AIDS
• prolonged exposure to sunlight or radiation
• eye injuries
• certain medications, like steroids

Surgery is recommended when cataracts start to interfere with daily activities like reading or driving. During surgery, the cloudy lens is replaced with a clear artificial lens.

Age-related macular degeneration

Age-related macular degeneration (AMD) affects the central part of the retina, leading to blurry or distorted vision, particularly in the center of your field of vision.

AMD is classified into two types: dry and wet. Both types involve the buildup of fatty deposits, called drusen, beneath the retina. Dry AMD can progress to wet AMD, in which abnormal blood vessels grow under the retina. These fragile vessels can leak fluid or blood, leading to vision loss.

While there is no cure, lifestyle changes such as quitting smoking and eating a nutrient-rich diet can slow progression of AMD. There is some evidence supporting the use of daily vitamin supplements containing vitamin C, vitamin E, beta-carotene, zinc oxide, and cupric oxide. This supplement, known as AREDS2, is named for the Age-Related Eye Disease Study. Discuss the potential risks and benefits of vitamin supplements with your doctor prior to starting. Ophthalmologists can administer treatment for advanced forms of AMD.

Glaucoma

Glaucoma is a group of eye conditions that damage the optic nerve, often due to high eye pressure. It can cause gradual vision loss, usually starting with peripheral vision.

Glaucoma is classified as primary or secondary, and open-angle or closed-angle. Primary glaucoma develops without an identifiable cause, while secondary glaucoma results from an underlying condition like eye trauma, diabetes, or long-term steroid use. Open-angle glaucoma progresses slowly, with a gradual increase in eye pressure, whereas closed-angle glaucoma occurs suddenly, causing a rapid rise in pressure and requiring urgent treatment.

Without treatment, glaucoma can lead to blindness. Treatments include prescription eye drops, laser therapy, and surgery.

Diabetic retinopathy

Diabetic retinopathy (DR) occurs when, over time, high blood sugar damages blood vessels in the retina. This can cause blurry vision and, in severe cases, vision loss. This condition typically shows no symptoms until its advanced stages, but early signs may include floaters, dark spots, and fluctuating vision.

If you have diabetes, it’s crucial to have regular eye exams to detect early signs of retinopathy. Tight management of blood sugar, blood pressure, and cholesterol can slow disease progression, improve vision, and prevent further loss. In severe cases, treatment may involve injected medications, laser treatment, or surgery.

Causes of sudden blurry vision

Sudden blurry vision can be a scary experience and may have lasting effects. Sudden blurry vision can result from multiple causes, ranging from issues related to the eye or optic nerve to bodywide problems resulting from head injury, blood pressure, or blood flow.

Seek immediate medical attention if you experience sudden vision changes, which can be a sign of a medical emergency.

Stroke

A stroke occurs when blood flow to part of the brain is blocked by a clot (ischemic stroke) or when a blood vessel bursts, causing bleeding in the brain (hemorrhagic stroke). Both stroke types damage brain cells. If a stroke affects the part of the brain responsible for vision (the visual cortex), it can cause sudden blurry vision, double vision, or vision loss in one or both eyes.

Retinal detachment

A detached retina happens when the retina pulls away from the back of the eye. People with a retinal detachment experience painless vision loss in the affected eye. Early signs may include a sudden increase in floaters (tiny, shadowy shapes in vision) or flashes of light. If detachment occurs, it can create a “hazy curtain” effect in part of the vision.

Retinal detachment is a medical emergency that requires prompt treatment to prevent permanent vision loss.

Concussion

Head injuries, including concussions, can affect the eyes and lead to temporary blurry vision, dizziness, and difficulty focusing.

Migraine

Some migraines are accompanied by visual disturbances, including temporary blurry vision, blind spots, or flashing lights. This is known as a migraine aura. If an older person experiences these symptoms for the first time, they should contact their doctor.

Migraine-associated vision changes typically resolve within an hour. Managing stress, staying hydrated, and identifying migraine triggers can help reduce episodes.

Blood pressure spike or drop

Sudden changes in blood pressure, whether too high or too low, can cause temporary blurry vision.

Low blood sugar

Low blood sugar, also called hypoglycemia, can cause blurry vision. Hypoglycemia is more common in people with diabetes. Eating a small snack containing fast-acting carbohydrates, such as fruit juice, raisins, or saltine crackers, can help restore blood sugar levels and normal vision.

When to see a doctor

Regular eye exams can help detect and manage vision problems before they become serious or permanent. Schedule an eye exam if you experience persistent blurry vision.

See a doctor immediately if you experience:

• sudden vision changes, including blurry vision
• sudden vision loss in one or both eyes
• severe eye pain or headache
• flashes of light or a sudden increase in floaters
• difficulty speaking, weakness, or confusion along with blurry vision.