Wearing your contacts longer than you should, be it too many hours in a day, keeping them in overnight or too many weeks with a particular set of lenses, doesn’t seem particularly dangerous if you don’t notice any symptoms. You can save money by extending the life of your lenses, and you don’t experience the inconvenience of wearing glasses for a few hours each day.
This assumption, however, is wrong. Despite the fact that you may not notice any symptoms, overwearing your contacts is dangerous for your eyes in both the short and long term. In brief, wearing contacts compromises the amount of oxygen your eyes receive.
Regardless of how well your contacts breathe and fit, your eyes will still receive less oxygen than they would without lenses in. The contact lens covers the cornea which is the outer window of the eye. The cornea has no blood supply and therefore needs to use the oxygen from the atmosphere to provide it with nutrients. If the cornea does not receive this from the atmosphere, it has to obtain it in other ways and this leads to blood vessels growing towards the cornea. This can also lead to swelling of the cornea, breakdown on the corneal surface, or infection of the cornea. Keratitis is one such condition that can result from over-wearing of contact lenses. Keratitis involves the inflammation of the cornea, and causes bloodshot, watery eyes that are sensitive to light. It is often painful, and causes hazy vision. Keratitis often heals without causing any long-term damage, although if left untreated, keratitis can cause permanent scarring, partial blindness, and blurred vision. Contact lenses should be left out while your eyes are healing, and the lenses, solution and case that you were using when you began showing signs of keratisis should all be discarded.
Corneal abrasions can also result from the over-wearing of contacts, and involve a scratch or scrape on the surface of the cornea. Symptoms may include sensitivity to light, pain, squinting, excessive tears, and the feeling of something being stuck or caught in your eye. Corneal abrasions are best detected by an optometrist, who will have the equipment to view your eye with enough magnification to detect any abrasions. Small abrasions may not need specific treatment, while large abrasions are often treated with an antibiotic to prevent infection. Regardless, it is important to refrain from wearing contacts while your eyes are healing, as not to perpetuate the problem.
Corneal edema is the technical term for swelling of the cornea, resulting from a lack of oxygen. The risk of corneal edema increases with lens usage, and is particularly problematic for those who sleep in their contact lenses, as the eye is cut-off from oxygen by the eyelid as well as the lens. Corneal edemas can cause blurred vision, and possibly irritation or pain, as well as corneal abrasions or infection, if the problem is allowed to continue untreated. Contact lenses should be removed and left out while the cornea is healing from a corneal edema.
Corneal ulcers refer to infections of the cornea, and result more often from soft contacts than hard lenses. Often caused by over-wear, corneal ulcers can also be caused by improper cleaning and overly tight lenses. Typically, the eye will become red and painful as a result of the infection. Tearing, discharge, sensitivity to light, and blurred vision may also be present. It is important to visit an optometrist if you suspect you may have an infection. However, even if it has been treated properly, a corneal ulcer may still cause scarring on the cornea. Because of this, it is extremely important to avoid behaviours which may cause corneal ulcers in the first place. The risk of infection with certain types of contact lens can be as frequent as one in five hundred patients. In comparison the risk of infection with LASIK is one in eight thousand patients.
Contact lenses can be a great alternative to glasses, and, if worn properly, shouldn’t pose any additional problems for your eyes. That being said, it is dangerous to assume that contacts can be worn longer than is advised without consequences. Even if you don’t immediately notice – your eyes will. Do yourself and your eyes a favour, and carefully monitor how long you are wearing your lenses. If you are planning a late night out, then wear spectacles during the day.
If you do experience any of these symptoms, stop wearing your contacts immediately, and throw away the contacts that have been irritating your eyes. If your eyes don’t clear up within a few days, make an appointment to visit your optometrist.