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It's easy to take contact lenses for granted. They're so convenient and accessible that many of us pop them in each morning without a second thought. In reality, they're a relatively new medical marvel -- the first modern plastic contact lens wasn't introduced until almost 1950. Or, as Dr. Robert Kinast puts it, "We think of contact lenses as being so normal, but 100 years ago, nobody walked around with little pieces of plastic over their eyes."Dr. Kinast, the vice chair of ophthalmology at Legacy Devers Eye Institute and co-founder of GentleDrop, says, "Contact lenses are foreign bodies and should be treated with respect." To that end, we talked with eye experts to explain how to care for contact lenses and when to replace them.How long do contacts last?The lifespan of your contact lenses depends on a few factors. Dr. Meenal Agarwal, optometrist and podcast host, explains, "Soft daily disposables are single-use, so you need to discard them after one day." At the other end of the spectrum, she says that "hard lenses can last one to two years with proper care." The most important rule, according to Dr. Agarwal, is to always follow the replacement schedule recommended by your eye doctor.Soft lenses are the most commonly worn contact lenses, according to Dr. Jovi Boparai, ophthalmic surgeon and co-founder and CEO of CorneaCare. He explains that these lenses "range from daily disposables to weekly, biweekly or monthly." However, "Rigid gas permeable contact lenses can last much longer, ranging from months to a year." These lenses are made of hard plastic.While most contact lenses will last for the intended duration, some factors may shorten their lifespan. For instance, dust and smoke may cling to your lenses and make them unusable. If there is a wildfire in your area or a high allergen count and your lenses start to feel uncomfortable, you may want to toss them early.How to know if your contacts are expiredThe quickest way to gauge whether your contacts are expired is to look at the date on the box. Dr. Boarpai says that unopened contact lenses generally have a shelf life of one to four years from the date of manufacturing.Beyond reviewing the expiration date, you should pay attention to how your lenses look. According to Dr. Boparai, old lenses may show discoloration or damage. He also warns that expired contacts can develop deposits -- meaning a buildup of residue on the lenses.On the other hand, your contacts may still be expired, even if they look great. Dr. Agarwal warns, "The lenses may look the same as they did on the first day, but that doesn't mean they're still safe to use." In short, you should defer to the expiration date first but also ditch your lenses if there is obvious damage or they become painful. Anna Gragert/CNETExpired contact lens symptomsIt's easy to lose track of your lens-changing schedule when life gets busy. If that happens, your lenses may let you know they're expired before you even have a chance to track down the date on the box."Wearing expired contacts can cause redness, pain or discomfort, irritation, blurry vision, excessive dryness and/or infections," warns Dr. Agarwal. You should take these symptoms as a red flag. The doctor advises, "If you experience any of these symptoms, remove the lenses and consult your eye doctor."According to Dr. Boparai, additional symptoms may include "burning, watery eyes, light sensitivity, discharge, foreign body sensation and eyelid swelling."Signs that your contacts are ready to be replacedIt's worth noting that you won't always experience symptoms when your contacts are ready to be changed. Sticking to the appropriate schedule is vital, even if you think your contacts could last a few more weeks. As Dr. Agarwal explains, "Most of the time, you will not have any symptoms when your lenses are ready to be replaced."However, the doctor reiterates that if you've overworn contacts for a long time, you may notice vision problems, painful symptoms or "a torn or damaged lens and/or a buildup of deposits or debris on the lenses." This means it's definitely time to switch to a fresh pair.How often should I change my contact lenses?The simplest answer is to follow the recommended duration of use. Dr. Boparai reiterates that you should change lenses based on "the lifespan of the contact lenses as recommended by your eye doctor."You may also want to consider the length of time you're wearing your lenses per day. According to Optometrists Network, about half of all contact lens wearers don't comply with the wear schedule recommended by their doctors. This can lead to something called contact lens overwear syndrome, which occurs when your lenses obstruct your eyes' ability to absorb oxygen. Left untreated, you may experience bloodshot eyes, infection or a damaged cornea.Both doctors we spoke to insisted that you should never sleep in contacts unless it's recommended by a doctor. This may help prevent overwear syndrome, and it also gives you an incentive to check your lenses each morning to make sure it's not time to change them out. Olesia Bekh/Getty ImagesHow to care for your contact lensesProper care for your contacts not only helps maximize their lifetime but may also prevent eye infections. First and foremost, you should always handle your contact lenses with clean hands, according to the American Academy of Ophthalmology (AAO). The organization also recommends using a "rub and rinse" method each time you use your lenses. This means you should first rub your lens with clean fingers and then rinse it with a contact lens solution.Contact lenses carry an increased risk of eye inflammation and infection, says Dr. Boparai. He adds that proper contact lens hygiene includes rinsing the lenses for 10-20 seconds before wear and making sure you don't touch your cornea when you take the lenses in and out of your eye. Dr. Boparai also recommends changing your contact lens solution every day.Dr. Meenal emphasizes the importance of storing your lenses "in a clean case and replacing the case every three months." She warns that you should never use water or saliva to clean your contact lenses.How to prevent contact lense-related eye infectionsThe most common eye infection associated with contact lenses is keratitis, which the Mayo Clinic describes as an inflammation of the cornea. Unfortunately, this infection happens a lot. The Centers for Disease Control and Prevention analyzed contact lens-related infections between 2005 and 2015 and determined that "keratitis from all causes, including contact lens wear, results in approximately 1 million clinic and emergency department visits annually."The AAO says that wearing extended-wear lenses, sleeping in your lenses and keeping a dirty lens case can all make you vulnerable to this type of infection. The Mayo Clinic warns that poor contact lens hygiene allows for the growth of bacteria, fungi and parasites that can infect your cornea.Dr. Agarwal adds to this advice, explaining that contact lens wearers should never share or reuse lenses. She also warns that you should "avoid wearing contacts in pools, hot tubs or the shower." Importantly, the doctor recommends that you remove your lenses at the first sign of discomfort. And don't use saliva to clean your lenses, as Dr. Boparai warns this makes you more vulnerable to infection.When to contact an eye doctor if you wear contact lensesThe AAO says that patients who are at low risk for ocular disease should get an eye exam at least every two years until the age of 64, unless their doctor recommends more frequent exams. After the age of 65, annual eye exams are the standard.However, even if you're not high risk, you should see your eye doctor "as soon as possible if you experience eye pain, persistent redness or swelling, intolerance or discomfort with your lenses, sudden blurry vision, unusual discharge, excessive tearing and/or sensitivity to light." This is according to Dr. Agarwal, who adds that you should remove your lenses and not wear them again until your doctor gives you the go-ahead.Vision changes also call for another visit to the eye doctor, says Dr. Boparai. He emphasizes that if you have uncomfortable symptoms or vision loss, "Your eye doctor will help guide management to keep your eyes comfortable and clear."The bottom lineWhen in doubt, don't overwear your contact lenses. You should throw them out as soon as they expire, start to hurt your eyes or appear damaged. Wearing lenses improperly isn't just uncomfortable -- it can also lead to serious infections.Don't be afraid to call your eye doctor if something seems wrong.
