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Why Astigmatism Causes Blurry Vision, Especially at Night

Why Astigmatism Causes Blurry Vision, Especially at Night

Benjamin Bert, MD •

  • Astigmatism is a vision disorder that affects how the eye processes light
  • Astigmatism occurs when the eye is shaped more like an oval than a sphere, which distorts the light that enters causing blurry vision
  • Astigmatism is fairly common, affecting about one in three Americans and it occurs more frequently as you age
  • Astigmatism causes blurry vision no matter what time of day, but it becomes more noticeable at night due to the contrast between dark and light

    "The cornea is not perfectly round. It's actually slightly oval. It's a very subtle difference, but it's important from a visual perspective," says Manhattan-based ophthalmologist Robert Friedman. 

    Astigmatism is fairly common — it affects about one in three Americans, according to the American Academy of Ophthalmology. And it occurs more frequently as you grow older. For example, an estimated 23% of 20- to 39-year-olds, 28% of 40 to 59-year-olds, and 50% of those 60 and older have astigmatism.

    The condition can occur with nearsightedness (myopia) or farsightedness (hyperopia), and there are several methods to treat it. Learn more about astigmatism, how light affects the condition, and ways to help alleviate the symptoms.

    Astigmatism is one of four kinds of, what are called, refractive errors, in which the shape of the eye doesn't bend light correctly, causing blurred vision. The other types of refractive errors are: 

    • Nearsightedness: Difficulty seeing unless objects are close to the eyes.
    • Farsightedness: The ability to see clearly if objects are far away, but close-up vision is blurry.
    • Presbyopia, or when you have trouble focusing on objects up close and need reading glasses. 

    Patients can have more than one of these refractive conditions simultaneously. 

    Corneal vs. lenticular astigmatism

    Most people are born with astigmatism. Usually, it's either because their cornea — the clear window in front of the eye — is more oval than round or their lenticular lens — is overly curved.

    Both kinds of astigmatism can occur in one or both eyes, but corneal astigmatism is most common, says Friedman.

    How astigmatism affects light perception 

    Ophthalmologists say blurry vision from astigmatism is the same no matter what time of day it is. However, blurry vision can become especially noticeable at night because of the contrast between light and dark. 

    "People will say, 'I have trouble driving at night, but not in the day.' And it's not that in the daytime, they don't have the refractive error, it's just that they're able to overcome it a lot easier than at night when there's less light," says Anna Park, an ophthalmologist in the Martin P. Kolsky Group Chartered in Washington, DC, and an attending physician at the Washington Hospital Center. 

    The reason vision may not be as blurry during the day is because there's less light for your eye to focus. To compensate, the pupil dilates to let in more light. A larger pupil means more of the cornea and lens are being used to focus the light. Using more of these surfaces increases the symptoms of astigmatism or other refractive errors.

    "Night vision is the same as day vision, it's just that the light rays aren't focused on your retina as they should be, so the picture you get is blurred and distorted. In general, in lower light, refractive errors come out more often," says Park. 

    Most astigmatisms are mild, Chan says. "So people may not notice the problem during the day. But at night, lights — headlights, stop signs — will seem to come at you." 

    As an aside, Park says that it's important to note that screens and devices don't cause astigmatism or have any effect on them since it's a physical condition of the eye's shape and not based on behavior.

    Experts agree the main symptom of astigmatism is not seeing clearly. That may then cause other symptoms, including:

    • Blurred vision at all distances: People with astigmatism may complain of blurred vision for objects both up close and far away, says Park. 
    • Eyestrain and headaches: "Eyes muscles are trying to focus, and if things are not clear, you can get eyestrain," Park says. This may lead to headaches.
    • Streaky vision: Astigmatism may cause lights to seem streaky, says Vicki Chan, an ophthalmologist at Kaiser Permanente in Los Angeles. While viewing an eye chart in a doctor's office, the "E" may appear offset, or the chart letters may look like one is on top of the other, as opposed to the overall blurriness of other conditions.
    • Circular lights appear as ovals: "If you look at a circular light from far away and it [has] an ovoid distortion to it, that would be astigmatism," Friedman tells Insider. But ovoid, or oval, distortions are often difficult to perceive, he says.  
    • Difficulty functioning at certain distances: Just because a person has astigmatism, doesn't mean all tasks will be impacted similarly. Some people may be able to read if their astigmatism aligns in a certain direction, Friedman says, but have problems with other tasks that require seeing from far away. 

    How to treat astigmatism

    If you have a history of vision problems, it may be time to consult a professional.

    "When we prescribe glasses or contacts, what we're doing is providing a prescription that'll help focus the light coming into the eye and to the retina so that the picture is clear," says Park. 

    • Glasses: Prescription glasses refocus the images and lights to correct astigmatism, says Chan. Tinted glasses reduce some glare but won't help with astigmatism.
    • Contact lenses: If it's strong enough to require contacts, toric lenses have two light-bending powers that cross perpendicularly to treat astigmatism. 
    • Laser surgery: Lasik laser surgery can be used to correct astigmatism. If a patient has corneas deemed too thin for Lasik, photorefractive keratectomy (PRK) is an option. 


    Blurred vision at all distances, eye strain that causes headaches, and streaky vision are a few key signs of astigmatism. Most people are born with astigmatism but in rarer cases, astigmatism can be caused by trauma.

    In general, in lower light, refractive errors come out more often, which is why people with astigmatism may have trouble seeing or driving at night. The condition exists in the daytime, too, it's just exacerbated by the dark.

    Moreover, astigmatism may change — for the better or worse — with age, so it's important that if you have blurred vision, it's best to see a healthcare professional for a diagnosis.

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    The 4 Best Vitamins for Eye Health and Which Foods May Improve Vision

    The 4 Best Vitamins for Eye Health and Which Foods May Improve Vision

    The 4 best vitamins for eye health and which foods — besides carrots — may improve vision

    • The best vitamins for eye health include vitamin A, vitamin C, vitamin E, and B vitamins.
    • Vitamin C may help protect against cataracts and slow the progression of age-related macular degeneration (AMD).
    • A deficiency in vitamin A can harm the cornea and retina, which can damage your vision. 

    In many cases, eating a balanced diet with plenty of fruits and vegetables is enough to keep your eyes healthy. But if you suffer from certain serious eye diseases, you may also need to add in vitamin supplements.

    Here are 4 of the most important vitamins you need to keep your eyesight sharp.

    1. Vitamin A

    "We've all heard that carrots are good for the eyes. This is in part because they have high levels of vitamin A," says Sunir J. Garg, MD, a Professor of Ophthalmology at Thomas Jefferson University.

    This is because vitamin A helps produce the pigments that allow your retina to work properly. When you don't have enough vitamin A, you may have trouble seeing in low light.

    "Thankfully this type of vision loss can often be improved when vitamin A levels go back to normal," Garg says. This means you likely don't need a huge boost of vitamin A, as long as you are getting the recommended daily value, between 0.7mg and 0.9mg.

    Here are some foods that are rich in Vitamin A: 

    vitamin a

    2. B vitamins

    B vitamins — like B6, B12, and folic acid — can help improve eye health by preventing age-related macular degeneration (AMD), a condition in which your retina deteriorates over time, causing blurry vision. This is because B vitamins reduce your blood levels of homocysteine, an acid that can affect the arteries of your retina and is an independent risk factor for AMD.

    A deficiency in B vitamins can also lead to problems with the optic nerve, the tissue responsible for taking the images from the eye to the brain. In severe deficiency, it can cause reduced vision or blind spots. 

    Here's how you can get more Vitamin B6, a crucial B vitamin: 

    Vitamins 09

    3. Vitamin C

    Cataracts, the cloudy areas that develop on the lens of your eye, are among the most common reasons your vision can get worse as you get older.

    Antioxidants help protect against free radicals that can cause changes to the lens in your eye, leading to a cloudy appearance that disrupts your vision.

    Several studies have shown that getting at least 40 mg per day of vitamin C (for reference, the recommended value is 60 to 90mg per day) can help prevent cataracts from developing. But be careful not to get too much, since a very large 2013 study found that getting over 500mg of vitamin C may actually increase the risk of cataracts for certain groups, like men who are smokers or obese.  

    Studies also show that vitamin C can also help slow the progression of AMD by strengthening the blood vessels in your eye that support the retina. A 2016 study found that people with higher intake of vitamin C were significantly less likely to suffer from AMD.

    Vitamins 05

    4. Vitamin E

    Vitamin E also acts as an antioxidant in your body and studies show that it may protect you from vision loss in old age.

    More research is needed, but some studies suggest that eating a diet rich in vitamin E or taking vitamin E supplements over a long term may help prevent cataracts and AMD.

    2005 study found that people who took vitamin E supplements were less likely to develop cloudy eye lenses over the course of 5 years. However, a 2001 study found that taking a daily 400 IU vitamin supplement had no effect on eye cloudiness.

    Some foods that are rich in vitamin E include:

    Vitamin E foods


    Getting enough of these important vitamins in your diet can go a long way towards strengthening and protecting your eyesight. In most cases, you likely won't need to take additional supplements unless you have a vitamin deficiency.

    "For most people, the amount of these vitamins that we get from a well-balanced diet is plenty," Garg says. 

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    Considering Your Laser Vision Correction Options

    Considering Your Laser Vision Correction Options
    LASIK and other types of Laser Vision Correction procedures have been performed in the United States since 1994 with over 15 million procedures performed. These remarkable procedures have evolved as the technology has improved over the years, indications have expanded allowing more patients to enjoy clearer vision without glasses or contacts, and far superior results are obtained when compared to those of the early procedures.

    Despite the widespread acceptance of LASIK and the vast amount of public information that is readily available, there are still certain areas of particular interest, as well as sources of potential confusion, to patients who are considering the procedure. In this report, the first of a series, we will examine and clarify some of the most common issues and choices patients face when considering Laser Vision Correction.

    Bladeless All-Laser LASIK vs. Microkeratome Blade LASIK

    In LASIK, a microscopic corneal flap is created under which an excimer laser applies the patient’s prescription. Healing of the corneal flap is quite rapid, allowing highly functional vision within 12 hours. The corneal flap can be made with a femtosecond laser (bladeless) or with an automated instrument called a microkeratome (using a microscopic blade).  Currently, about two-thirds of the procedures in the United States are done with a microkeratome. Both are excellent methods of performing LASIK, but most importantly, there are no statistical differences in visual outcomes between the two procedures. The prescription that is applied to the eye is the same with both methods and the success rate in achieving 20/20 vision is the same.  There are, however, important differences between the two methods. Microkeratome technology requires more training and experience, yet it is significantly less expensive, takes less time in surgery, and nearly always causes less discomfort than bladeless. Bladeless technology may be a better choice in patients with certain corneal parameters and is generally easier to learn and to use by surgeons who are less experienced in corneal surgery. It is important to choose a surgeon who offers both technologies, allowing the selection of the best procedure for you.

    I Have Good Distance Vision but I Hate My Reading Glasses! Is Laser Vision Correction for Me?

    Over the past decade, several procedures such as LTK, CK, and multifocal IOLs have been promoted as being able to eliminate reading glasses in patients over 40 while not reducing their distance vision. Despite the desirability of such a procedure, there is no technology that will create normal vision both at near and at distance simultaneously in an eye of a patient over the age of 40. As all patients who wear only reading glasses can attest to, the distance vision is blurred when looking through a reading prescription. Unfortunately, research testing of bifocal laser prescriptions has been uniformly unsuccessful… and, not surprisingly, the laser “time machine” which reverses the normal aging process has yet to be invented! 

    Nonetheless, LASIK may eliminate distance and reading glasses simultaneously in patients over 40 given the correct scenario. If a patient can function well with one eye corrected for distance and one corrected eye for near, which is called monovision, and which many patients already achieve by wearing a distance contact in one eye and a reading contact in the other eye, then LASIK monovision is a highly successful option. LASIK monovision corrects one eye for distance and one eye for near, allowing a patient over age 40 to see both without glasses or contacts.

    In patients who wear reading glasses only who are not regular contact lens wearers, a short trial of a reading contact lens in the non-dominant eye with their current Eye Doctor can usually determine if they can have LASIK monovision.

    Recurrent Contact Lens Infections: Can I Still Have LASIK?
    Does LASIK Correct Astigmatism Better than Glasses and Contact Lenses?

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    Recurrent Contact Lens Infections and the LASIK Alternative

    Recurrent Contact Lens Infections and the LASIK Alternative

    Recurrent episodes of irritation and infection from contact lenses may range in severity from mild redness and discomfort during prolonged wear, to more severe and sight-threatening complications such as bacterial keratitis and corneal ulceration. Fortunately, most contact lens “infections” are not infections at all, but instead are chronic recurrent inflammatory or allergic conditions associated with contact lenses. Patients sometimes forget, that no matter how advanced contact lens technology may become, a contact lens is still an artificial plastic foreign body in the eye which nature never intended to be there.

    Most contact lens irritations which cause redness, soreness, and a mild discharge can be attributed to simple problems such as poorly fitting or dirty contacts, contact lens overwear, or an underlying dry eye condition. In these cases, there is no real infection present, although patients may refer to the redness and irritation incorrectly as “conjunctivitis”.  Conjunctivitis, or pink eye in layman’s terms, more correctly refers to infection of the conjunctiva and may be viral or bacterial in etiology.

    One special case of chronic contact lens irritation is Giant Papillary Conjunctivitis, or GPC, in which the patient develops an allergic response to proteins that bind to the contact lens. GPC results in redness, a foreign body sensation, itching, a mucous discharge, and a proliferation of papillae, or bumps, on the inner surface of the lids which cause discomfort. Unfortunately, medications do not treat this condition effectively, the only alternative being a drastic reduction of contact lens wearing time, or in many cases, a complete cessation of contacts.

    Bacterial keratitis and corneal ulceration occur infrequently in patients who do not abuse contacts but are very serious sight-threatening conditions that cause severe pain, inflammation, light sensitivity, and if untreated, may cause scarring, corneal perforation, and permanent loss of vision. The risk of bacterial keratitis increases significantly in patients using extended wear lenses, especially if lenses are worn more than two weeks continuously.

    Patients with chronic recurrent contact lens irritation and GPC may be excellent candidates for laser vision correction and LASIK. Very simply put, contact lenses cannot irritate the eye if they are not needed. In addition, patients who may not be able to wear contacts comfortably due to an underlying dry eye condition may still be excellent candidates for LASIK. Certain precautions and procedures must be undertaken in patients with dry eye syndrome undergoing LASIK; however, LASIK does not permanently worsen dry eyes.

    LASIK may be an outstanding alternative to contacts in patients who have previously had serious corneal infection and ulceration. Microscopic scarring of the cornea from infection or ulceration is not an absolute contraindication to laser vision correction and LASIK. In fact, the laser vision correction procedure can be specifically designed to remove the microscopic scar tissue as well as correct the patient’s prescription.

    Next in our series:  “I’m over 40 and I hate these reading glasses!”  Is LASIK Monovision for me?

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    “I’m Over 40 and I Hate These Reading Glasses!” Monovision: The LASIK Alternative to Reading Glasses

    “I’m Over 40 and I Hate These Reading Glasses!”  Monovision: The LASIK Alternative to Reading Glasses

    Patients who have normal distance vision will usually require reading glasses beginning in their early 40’s.  The aging of the proteins inside the human lens leads to a progressive loss of focusing power, eventually resulting in blurred vision at near.  Many patients over the age of 40 can use simple over-the-counter reading glasses for their near vision. It is not surprising that the newly found need for reading glasses is a significant annoyance to people who have previously enjoyed clear vision without glasses for their entire lives. As a consequence, one of the most frequently asked questions about LASIK is whether it will correct the need for reading glasses.

    The simple answer is yes, the more complete answer is that it requires LASIK monovision.

    As many patients are aware, reading glasses work only for near vision and make everything blurry at a distance. If a patient has both eyes corrected for reading with glasses (or contacts or LASIK), then distance vision is blurred. Only one eye can be corrected for reading if distance vision is to remain clear. The situation where one eye is corrected for distance and the other eye is corrected for reading is called monovision.  The resultant vision is a compromise, and a combination of distance and near vision, and although not absolutely perfect at distance or near, many patients adapt to monovision extremely well. There seems to be a direct correlation between the ability to adapt to monovision and how much an individual dislikes reading glasses.

    Many patients use monovision in their contact lenses. If a person has normal distance vision, they can wear a single reading contact in one eye. If a person wears bifocal glasses, they can wear a reading contact in one eye and a distance contact in the other eye.

    If a patient is an acceptable candidate for LASIK based upon a number of other factors, LASIK can create virtually any reading or distance prescription, and therefore, can create monovision as well. Prior to having LASIK monovision, a patient must undergo a monovision contact trial in order to test their ability to function and adapt to the vision. Virtually any eye care provider can provide a monovision contact lens trial without requiring the purchase of contacts. Patients typically know right away if they can adapt to monovision and if it would be successful in reducing or eliminating their dependence on glasses and contacts. Patients who are successful with Monovision LASIK are able to enjoy vision at distance and near… without searching for those annoying reading glasses!

    Next in our series of articles:

    “Seeing Without Glasses after Cataract Surgery: Your Lens Implant Options”

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    Does LASIK Correct Astigmatism Better Than Glasses or Contact Lenses?

    Does LASIK Correct Astigmatism Better Than Glasses or Contact Lenses?

    The second article in our series “Considering your Laser Vision Correction Options” addresses the frequently asked question,

    “Does LASIK correct astigmatism better than glasses or contact lenses?”

    In order to understand how laser vision correction corrects astigmatism, it is important to understand the nature of astigmatism, how it causes blurred vision, and how it can be corrected by different methods.

    Astigmatism is not a disease, but rather a refractive error of the eye which simply causes blurred vision. If the cornea (the front window of the eye) has a surface curvature which is spherical, such as the shape of a basketball, the eye has no astigmatism. If the cornea has a toric shape, like the surface of a football, it has two different curvatures on the surface, and has astigmatism. These two curvatures are usually at right angles to each other with one curvature steeper and one flatter. A greater difference in curvatures creates a larger amount, or magnitude, of astigmatism.

    In addition, astigmatism also has an axis (direction) which is determined by the orientation of the steeper curvature of the cornea. Put another way, the football shape of the cornea can be pointed in any direction like the needle of a compass.  Thus, astigmatism has a magnitude and a direction which are equally important.

    Glasses and contacts correct blurred vision from astigmatism by using the opposite shape of the correcting lens to “cancel out” the abnormal shape of the eye. For this reason, the frame of the glasses or the fit of the contacts must match exactly the correct magnitude and direction of the astigmatism of the eye. Any deviation in the compensating lens will cause blurred or fluctuating vision. This is why patients with astigmatism and glasses can tolerate very little twisting or maladjustment of the frame as it sits on their face. Similarly, patients with toric (astigmatism correcting) contact lenses frequently notice large fluctuations in vision as the contact lens spins on the eye. These problems arise because glasses and contacts simply compensate for the abnormal shape of the underlying cornea by adding the opposite shape in the correcting lens in front of the eye.

    Laser vision correction and LASIK, on the other hand, actually correct the astigmatism by reshaping the cornea, eliminating the two different curvatures, thereby creating the correct spherical shape of the cornea. Laser vision correction actually corrects astigmatism, it does not compensate for the refractive error in a similar manner to glasses and contacts.  As a result, patients with astigmatism frequently notice better vision with LASIK than with contacts or glasses. In fact, with the newest laser software, LASIK can frequently correct larger magnitudes of astigmatism than can even be placed in glasses or is available in contacts. In addition, patients with small amounts of astigmatism who do not wear toric contacts notice better vision after LASIK than with spherical contacts.


    Recurrent Contact Lens Infections and the LASIK Alternative


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    You may have heard about someone having an eye transplant, but what exactly does that mean? Medical science has no way to transplant whole eyes at this time. One group of researchers hope to be able to perform whole eye transplants within a decade. However, when someone receives a transplant today, they are usually having a corneal transplant. Donor corneas make this amazing, sight-saving surgery possible.

    Your eye is a complex organ connected to your brain by the optic nerve. The optic nerve sends visual signals from the eye to the brain, where they are interpreted as images. The optic nerve is relatively small, varying in length between 1.3 and 2.2 inches, and at its widest point, inside your cranial cavity, it is still less than one-fifth of an inch wide. Yet the optic nerve is made up of more than one million tiny nerve fibers, much like a fiber optic cable. Once these nerve fibers are cut, they cannot be reconnected. That is why it’s impossible to transplant a whole eye. Even if a surgeon could implant the eye into the eye socket, the eye still would not be able to transmit signals to the brain through the optic nerve and thus would not provide sight.


    Cornea transplants are the most common use of donated eye tissue. Each year, nearly 47,000 cornea transplants are performed to restore vision in people with corneal injuries or keratoconus. But it is important to remember that other parts of the eye are equally vital in the mission to save sight.

    Corneal transplantation is more than a century old. A healthy, clear cornea is necessary for good vision. If your cornea is injured or affected by disease, it may become swollen or scarred. A cornea with scarring, swelling or an irregular shape can cause glare or blurred vision. In a corneal transplant, a surgeon removes the damaged or unhealthy cornea tissue. She puts a clear donor cornea in its place. There are several corneal transplant surgery options available, depending on the situation.


    Amniotic membrane transplantation (AMT) has a well-established history. For problems affecting the sclera or the conjunctiva, doctors can transplant amniotic membranes. These membranes are taken from donated placental tissue and can be grafted on the surface of the eye as needed or used as a dressing or bandage of sorts. They can be temporary or permanent. These membranes help heal and regenerate surface tissues of the eye. Surgeons have also been able to successfully perform eyelash transplantation. This can restore eyelashes lost due to burns, injury and other medical conditions. Doctors continue to explore whether it is possible to transplant other parts of the eye. In July 2010, French doctors transplanted eyelids and tear ducts as part of a full-face transplant. Eyelids have been included in other face transplants in recent years as well.Today, researchers are replacing damaged retinal cells with healthy transplants. In clinical trials, researchers have used human stem cells to grow retinal pigment epithelium (RPE) cells. In the near future, we can expect RPE transplants. This is good news for people suffering from macular degeneration and Stargardt disease.


    Anyone can be an eye donor, regardless of age, race or medical history. At the time of death, medical professionals will determine whether your organs and tissues are suitable for transplantation or research.


    First, tell your family you want to be an eye donor when you die. Eye banks—the agencies that help get eye donations to medical and research institutions—will always ask your family if you told them you wanted to donate your organs. This is true even if you have an advance directive—legal documents that spell out your wishes for end-of-life care and other decisions.

    In many states, you can sign a card at the driver’s license bureau stating that you want to be an organ donor. You may specify whether you wish to donate your eyes, organs or other tissues.

    To learn more about becoming a donor in your state, contact your area eye bank or the organ procurement organization (sometimes called OPO or OPA) for your region. They will explain how you can make your organ, eye and tissue donation wishes known.

    If you choose to be an eye donor, you can be proud knowing you are helping to improve the quality of life for someone with little to no sight.

    David Turbert
    Reviewed By: G Atma Vemulakonda, MD
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    Staring at your computer screen, smartphone or other digital devices for long periods won’t cause permanent eye damage, but your eyes may feel dry and tired. You may develop blurry vision, fatigue or eye strain. Some people also experience headaches or motion sickness when viewing 3-D, which may indicate that the viewer has a problem with focusing or depth perception.


    Normally, humans blink about 15 times a minute, but studies show we blink half to a third that often while using computers and other digital screen devices, whether for work or play. Extended reading, writing or other intensive “near work” can also cause eye strain.


    • Sit about 25 inches, or arm’s length, from the computer screen. Position the screen so your eye gaze is slightly downward.
    • Many devices now have glass screens with considerable glare. Reduce glare by using a matte screen filter if needed.
    • Take regular breaks using the “20-20-20” rule: every 20 minutes, shift your eyes to look at an object at least 20 feet away, for at least 20 seconds.
    • Use artificial tears to refresh your eyes when they feel dry. Consider using a humidifier.
    • If a screen is much brighter than the surrounding light, your eyes have to work harder to see. Adjust your room lighting and try increasing the contrast on your screen to reduce eye strain.

    A note to contact lens users: Contact lenses can exacerbate eye dryness and irritation common to heavy users of computers and other digital devices often.

    Some tips: 

    • Give your eyes a break by wearing your glasses. 
    • Don’t sleep in your contact lenses, even if they are labeled “extended wear.”
    • Always use good cleaning practices.

    If your eyes are consistently red, blurry or watery, or they become sensitive to light or painful, see an Ophthalmologist.

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