Contact lens mistakes are extremely common, and many of them carry real consequences. Roughly 2 to 5 out of every 10,000 lens wearers develop a serious corneal infection each year, and the vast majority of those cases trace back to a handful of preventable habits. Here’s what you should never do with your contact lenses, and why each mistake matters.
Sleeping in Your Lenses
This is the single riskiest habit among contact lens wearers. Sleeping in lenses increases your chance of a serious eye infection six- to eightfold, according to CDC data. Even a single nap counts.
Your cornea gets its oxygen directly from the air. A contact lens already reduces that supply while you’re awake and blinking. When you close your eyes to sleep, the lens traps even more moisture and warmth against the cornea, creating ideal conditions for bacteria to multiply. In a CDC case series examining six patients who slept in their lenses, two required surgery, and most were left with permanent eye damage or vision loss. The infections often demanded weeks of antibiotic eye drops applied multiple times a day and numerous follow-up visits. Even lenses marketed for extended or overnight wear carry elevated risk compared to removing them each night.
Letting Water Touch Your Lenses
Tap water, shower water, pool water, lake water, and hot tub water all pose a threat. Water harbors a microscopic organism called Acanthamoeba that can burrow into the cornea and cause an infection that is notoriously difficult to treat, sometimes requiring months of medication. This type of infection remains a significant cause of permanent vision problems in the United States.
The CDC recommends removing your lenses before any water activity, including showering. If water does splash onto your lenses, take them out as soon as possible. Disposable lenses should be thrown away. Reusable lenses need a full overnight soak in fresh disinfecting solution before you wear them again. If you swim regularly and need vision correction, prescription goggles are the safest alternative.
Never rinse or store your lenses in tap water or distilled water, either. Researchers have called for manufacturers to add explicit warnings against this practice because it continues to cause preventable infections.
Topping Off Old Solution
Adding a splash of fresh solution to whatever is left in your case from yesterday feels harmless, but it significantly reduces the solution’s ability to kill bacteria. The CDC is direct about this: never mix fresh solution with old or used solution. The disinfecting chemicals in contact lens solution lose potency once they’ve been used. Topping off dilutes the new solution with exhausted liquid, leaving your lenses sitting in a bath that can no longer do its job.
The correct routine is to dump out all leftover solution every morning after you put your lenses in, rinse the case with fresh solution (not water), and let it air dry face-down on a clean tissue. Each night, fill the case with completely fresh solution before placing your lenses inside.
Wearing Lenses Past Their Replacement Date
Daily lenses are designed for a single day. Two-week lenses are designed for two weeks. Stretching that timeline saves a little money but invites problems. Research has shown that overwearing lenses leads to significantly more protein buildup on the lens surface, which in turn triggers inflammation of the inner eyelid. Symptoms include itching, mucus discharge, and a gritty sensation that makes wearing lenses increasingly uncomfortable.
The protein deposits also make the lens surface irregular, so bacteria and other microorganisms have more places to attach. Over time, the accumulated buildup can irritate the tissue on the underside of your upper eyelid enough to form small bumps, a condition called giant papillary conjunctivitis. Once this develops, you may need to stop wearing contacts entirely until it resolves.
Skipping Case Replacement
Even with perfect cleaning, bacteria form a sticky, protective layer called a biofilm on the inside of your lens case within weeks. Once a biofilm establishes itself, regular rinsing won’t remove it. Experts and the American Optometric Association recommend replacing your contact lens case every one to three months. A new case typically comes free with each bottle of solution, so there’s no reason to keep using an old one.
Using Saliva as a Wetting Agent
If your lens dries out or falls and you don’t have solution nearby, putting it in your mouth is one of the worst fixes available. Your mouth contains a dense and diverse population of bacteria that your eyes have no defense against. These organisms can cause corneal ulcers that threaten your vision. If you don’t have solution and a lens dries out, it’s better to go without the lens than to lick it and reinsert it.
Applying Makeup Before Inserting Lenses
The University of Rochester Medical Center recommends a specific order: put your lenses in before applying any makeup, and take your lenses out before removing makeup. This sequence minimizes the chance of trapping cosmetic particles, oils, or fibers between the lens and your eye. Loose powder eyeshadows, waterproof mascara, and cream-based products are especially likely to leave residue on a lens surface. If you use eyeliner, apply it outside the lash line rather than on the inner rim, where it can migrate onto the lens directly.
Ignoring Early Warning Signs
Many lens wearers push through mild discomfort, assuming it’s just dryness. But the early symptoms of a corneal ulcer, one of the most serious contact lens complications, start subtly: eye discomfort, a feeling like something is stuck in your eye, watery eyes, or mild lid swelling. These can escalate quickly into intense redness, severe pain, sensitivity to light, discharge, and blurred vision. In advanced cases, pus can collect inside the eye itself.
If you experience any unusual irritation, redness, or pain while wearing contacts, remove the lenses immediately. Do not put them back in to “see if it gets better.” A corneal infection that’s caught in the first 24 hours responds far better to treatment than one that’s been brewing for days under a lens you kept wearing.