Why do my eyes unfocus

Blurry, unclear, unfocused vision is one of the most common eyesight problems. And usually, it isn't anything to stress over. For instance, blurriness could signify that your glasses or contacts prescription needs updating.

Every once in a while, though, fuzzy vision signals something more serious. You should always investigate what's causing your blurry vision. Knowing the reason behind it can be the difference between experiencing the world in all its dimensions or not.

"Sight is such a valued sense, but there are still a lot of problems that fall through the cracks," said Rajiv E. Shah, MD, assistant professor of ophthalmology at the Atrium Health Wake Forest Baptist Medical Center in Winston-Salem, N.C.

Here are 15 of the most common culprits causing blurry eyes and what to do about them.

Nearsightedness (myopia), farsightedness (hyperopia), and astigmatism are refractive errors. They are some of the most common causes of blurry vision, according to the National Eye Institute (NEI).

They happen when the eye curve gets in the way of light focusing directly on the retina. The retina processes light rays into signals the brain can read.

Refractive errors may be some of the most straightforward errors to fix. In most cases, you only need a prescription from an optometrist or ophthalmologist for glasses or contact lenses. If you have one of those refractive errors, think about switching to bifocals, trifocals, or progressive lenses.

Additionally, LASIK laser surgery can permanently change the shape of the cornea to correct the problem in some people.

Presbyopia is also a refractive error, but it strikes most people after age 45, according to the National Library of Medicine. It means you have trouble focusing on things close up, like reading material.

So, if you find you need to hold magazines, books, and menus farther away from your face to read them, presbyopia could be causing your blurry vision.

As with other refractive errors, eyeglasses, contact lenses, and surgery can help you see better if you develop presbyopia. Dr. Shah explained that if you aren't farsighted or nearsighted and don't have astigmatism, reading glasses from the drugstore may be enough.

However, you should still see a healthcare provider to screen for any potential eye disease.

Conjunctivitis, commonly known as pink eye, is usually caused by adenoviruses. Those pesky viruses also cause the common cold, bronchitis, and sore throats, according to the Centers for Disease Control and Prevention (CDC).

Although not usually severe, conjunctivitis can spread like wildfire in schools and other crowded venues.

"Virus particles on surfaces can stay alive for about two weeks," said Kim Le, MD, a pediatric ophthalmologist with Henry Ford Health in Detroit.

Conjunctivitis usually goes away in one to two weeks without treatment, but if you have severe symptoms, talk to your healthcare provider about antibiotics or antiviral medications.

In the meantime, try cool compresses to alleviate itchiness, warm compresses to relieve swelling, or over-the-counter (OTC) eye drops to help with irritation, said Dr. Le. Additionally, wash your sheets (especially your pillowcases) and your hands often to prevent the spread of germs.

If you don't use contact lenses properly, they can cause sight-robbing infections.

Contact lenses move across the eye every time you blink, creating micro-scratches on the surface of your eye. Infection-causing microorganisms can get caught under the lens and seep into those scratches.

According to Dr. Le, sleeping with your contacts in "is a perfect petri dish to grow those organisms and cause corneal ulcers." Those are open sores on the cornea that can blur vision, according to the National Library of Medicine.

"Always, always take [contact lenses] out at night," added Dr. Shah, or toss disposable lenses at the end of the day.

You don't have to wear contact lenses to get eye infections that damage the cornea.

Herpes keratitis is an infection in the eye caused by the herpes virus and is one of the most common causes of corneal infections, according to the CDC.

You can get herpes keratitis by touching a cold sore on your lips and then touching your eyes. Bacteria and fungi that muscle their way in after an eye injury can also cause infection.

Treatments like eye drops and medications (such as antibiotics, antivirals, and antifungals) usually help. But prevention is one of the best methods of protecting yourself against eye infections—and your cornea will do much of the preventative work for you.

"The cornea is an amazing structure," said Bibiana Reiser, MD, assistant professor of clinical ophthalmology at the Keck School of Medicine of the University of Southern California and director of cornea and glaucoma services at Children's Hospital of Los Angeles. "It has a lot of [antibodies] that kill things directly on contact."

Cataracts are one of several eye problems that come with aging. According to the NEI, more than half of all people in the United States have cataracts by age 80.

Cataracts occur when the lens in the front of the eye becomes cloudy and blocks light trying to reach the retina. They usually take time to develop and don't cause pain or other symptoms. Some stay small and cause few problems.

Those that grow and interfere with vision are often treated with surgery to remove the old lens and replace it with a clear lens implant.

"That is one of the most successful surgeries in all of medicine," said Dr. Shah.

Glaucoma is a group of eye diseases that cause vision loss and blindness by damaging the optic nerve in the back of the eye, according to the NEI. Like cataracts, glaucoma is usually slow to develop.

Glaucoma, known as the thief of sight, happens silently without any symptoms. And once vision loss occurs, there's no way to bring it back.

"Patients with glaucoma don't even know it because the vision loss happens over decades," explained Dr. Shah. "There's really no way to suspect it other than regular eye evaluations."

Once a diagnosis is made, prescription medications, laser treatment, and surgery can help.

As you age, you have an increased risk of damage to the macula, an area near the retina's center that helps you see details and objects directly in front of you.

Age-related macular degeneration, or AMD, is the leading cause of vision loss for older adults and results in a loss of central vision, per the NEI. That can make everyday activities like driving and reading understandably challenging.

There's no treatment for early AMD, although specific vitamins and minerals can slow the damage in intermediate AMD and people with late AMD in one eye, per the NEI.

You can lower your risk for AMD by exercising, keeping your blood pressure and cholesterol healthy, not smoking, and eating a lot of green, leafy vegetables and fish.

"Really high sugars can lead to swelling of one's lens," said Dr. Shah. The swelling changes the shape of the eye and how it focuses, but the issue usually lasts only a couple of hours or days.

If you suspect you have high blood sugar, consult your healthcare provider immediately. You're at a higher risk for type 2 diabetes if you have a family history of high blood sugar.

Per the National Library of Medicine, besides blurry vision, other symptoms of type 2 diabetes include:

Frequent urination
Excessive thirst
Unexplained weight loss
Excessive hunger
Yeast infections
Tingling and numbness in the hands and feet

If you have undiagnosed type 1 or 2 diabetes, as well as diagnosed diabetes that isn't well-managed, you're at risk for diabetic retinopathy.

That occurs when blood vessels in the back of the eye become damaged and, in later stages, leak and start bleeding into the eye—resulting in seeing floating spots or streaks that look like spider webs, per the NEI.

If you know there's a problem, injections and laser surgery can help save your vision, but "unfortunately, this is the sneak thief of vision," explained Dr. Shah. "You can lose your vision from diabetes and not know you have diabetes."

Controlling your blood sugar can prevent diabetic retinopathy. If you have diabetes, make sure you get regular eye exams and regularly see a healthcare provider to check for diabetes.

You may already know that high blood pressure can lead to stroke and heart disease. What you may not know is that it can also cause a mini-stroke of the eye called vein occlusion, according to the National Library of Medicine.

"These patients feel no pain," said Dr. Shah. "They will wake up, and their vision is blurry." Blurry vision due to vein occlusion usually strikes just one eye, added Dr. Shah.

Treatments for vein occlusion—including medication to ease swelling of the macula—need to be given right away in order to be effective. Even then, you may experience vision loss.

To protect against vein occlusion, if you're over 50 and have high blood pressure, Dr. Shah recommended getting regular eye exams.

An ocular migraine is typically caused by spasms of the blood vessels that feed the part of the brain responsible for processing vision, Vicente Diaz MD, MBA, an assistant professor of ophthalmology and visual science and chief of ophthalmology at the Yale School of Medicine in New Haven, Conn., told Health.

"Symptoms include flashing lights, blind spots, and seeing patterns often with many jagged edges and corners," explained Dr. Diaz.

According to the American Optometric Association (AOA), an ocular migraine can occur with or without a headache and typically will last under an hour.

Dr. Diaz added that the term "ocular migraine" could also refer to a retinal migraine, a rare condition that causes loss of vision in one eye only and can indicate problems with retinal blood flow.

If, after banging your head pretty hard, you end up with vision issues, you might have a head injury.

"A concussion can lead to blurry vision, along with many other visual changes, such as double vision, difficulties with shifting gaze quickly from one point to another, problems focusing, and loss of binocular vision (eye alignment)," explained Barbara Horn, OD, past president of the American Optometric Association and president of Beach Eye Care & Audiology in Myrtle Beach, S.C.

If you think you have a concussion, contact a healthcare provider immediately to receive an evaluation.

Stress and anxiety can impact your health in many ways, including your vision.

"Many patients are not aware of how stress can impact their vision and eye health," said Dr. Horn.

"Stress can cause the pupils to unnecessarily dilate, and adrenaline can increase pressure on the eyes."

While the long-term impact of stress on the eyes can vary, most mild discomfort can be resolved by naturally lowering your stress level, explained Dr. Horn.

However, continuously heightened stress levels can cause permanent vision loss. In order to prevent stress-related vision problems.

Dr. Horn suggested maintaining a healthy lifestyle, taking visual breaks from screens and technology, and adopting other stress-reducing activities, like meditation and exercise.

If your eye blurriness and dryness are accompanied by inflammation in or around the eye, you could have uveitis.

The inflammation usually happens when your body is fighting an infection, or you have an autoimmune disease, according to the NEI. The most common causes of uveitis are corneal abrasion and eye trauma, infection, and autoimmune disease.

The prevalence of uveitis is pretty low, but the damage can be quite severe, said Dr. Diaz. Symptoms vary depending on what part of the eye is affected.

"Inflammation in the front part of the eye presents with redness, light sensitivity, and pain, whereas inflammation in the back part of the eye presents with floaters, fuzzy vision, and flashing lights," explained Dr. Diaz.

According to the NEI, treatment for uveitis usually involves steroids given in some form, from pills and eye drops to injections and implants.

Per the AOA, according to a 2017 study, at least 16 million people in the United States deal with dry eye syndrome.

"The most common types of dry eye syndrome are insufficient tear production or excessively rapid tear evaporation," said Dr. Diaz.

The tear film is essential for comfort, the health of the eye, and an optically clear surface. As light enters the eye, it first encounters the tear film and then the cornea, the most superficial and front part of the eye.

"If the tear film is unhealthy or lacking, then the cornea will become irritated, and light will be scattered rather than focused as it enters the eye, leading to blurred vision," explained Dr. Diaz.

Fortunately, most of the reasons for blurry vision don't threaten your eyesight. But there are times when you should visit an emergency room or contact a healthcare provider as soon as possible, such as: