Lens Types/Replacement and Wearing Schedules/Safety

The good news is that when contact lenses are cared for properly and the eye care practitioner's recommended wearing schedule is followed, contact lenses are a very healthy and popular option for correcting vision with little risk of complications.⁽¹⁾ In fact, the most serious form of complication, an eye infection often caused by a form of bacteria or other organism (often termed "microbial keratitis" or "corneal ulcer") which can result in some loss of vision, occurs on average in only four per 10,000 wearers.⁽²⁾ According to this study, the least risk of infection occurred with rigid gas permeable(GP) lenses (1.2/10,000), soft lenses worn daily (1.9/10,000), and daily disposable soft lenses(2.0/10,000). GP lenses are smaller than soft lenses, move more on the eye with the blink, and some initial awareness of the lens is experienced. However, total comfort is often achieved in one-to-two weeks and, because of the ability to bring in oxygen from the tears as well as through the lens, the optical quality of the harder surface, the greater resistance to deposits (i.e., less filming of the surface), and the ability to correct astigmatism, GP lenses have advantages in both the quality of vision and eye health. ^{(2, 3,4,5,6)} Conventional hard lenses(i.e., polymethylmethacrylate or PMMA) are not recommended as they do not provide any oxygen through the lens; therefore, swelling - and even distortion - of the front surface of the eye (i.e., the cornea) can result.^(7,8)

Daily disposable soft lenses have been increasing in use in recent years (15 percent of all soft lenses fit in the United States; 29 percent worldwide)⁽⁹⁾ because of the health benefits they possess.^(9,10) As they are not worn overnight and are thrown away every night, there is little risk of complications due to overnight wear, there is little-to-no build-up of deposits, and solution-related problems as well as case contamination problems, are essentially eliminated.⁽²⁾) This is important as lens contamination ^11,, and case contamination ^(12,13) are important factors in causing eye infection and inflammation. In addition, as it has been found that overnight wear of contact lenses increases the risk of eye infection by four - five times^(2,14,15,16) discarding the lenses every night greatly reduces the risk of this problem.

In recent years, conventional soft or "hydrogel" lenses are gradually being replaced by soft lenses containing "silicone" which increases the amount of oxygen going through the lens by three - five times. Therefore the majority of soft lenses being fit today are in a silicone-hydrogel (i.e., Si-Hy") lens material. ⁽⁹⁾) Although Si-Hy lens materials have not reduced the risk of an eye infection, especially if worn overnight or extended wear ^(2,17) the increased oxygen received by the eye results in less swelling (hypoxia) of the eye and appears to overall be a healthier option.^(18,19)

While it is apparent that today's generation of rigid gas permeable (GP) materials, silicone-hydrogel soft lens materials, and daily disposable soft lenses are quite healthy, following your eye care practitioner's lens care and wearing schedule recommendations are key factors in long-term safe and comfortable contact lens wear.

The answer to this question is no, although about half of disposable and frequent replacement lens wearers wear them longer than their recommended schedule.⁽¹⁾ The analogy can be made to not going to the dentist until you have a tooth ache or having a family history of glaucoma (a potentially blinding eye condition) and not seeing the eye doctor until some loss of vision is noticed. By the time the contact lenses feel uncomfortable, one of several problems could be present that could range from lid inflammation due to the lid coming in contact with a filmy contact lens surface during blinking - often resulting in having to stop wearing contact lenses for several weeks - to a serious eye infection that could potentially result in permanent loss of vision.⁽¹⁾ Loss of vision from a serious eye infection (termed "microbial keratitis" or "corneal ulcer") is quite rare but it has been found that wearing the lenses longer than prescribed by the eye care practitioner is a high risk factor.⁽²⁾ In addition, the risk of an eye infection is four - five times more common if the lens is worn overnight ^(1,3,4) and even a higher risk exists if the lens was not approved or prescribed for overnight wear.⁽³⁾
It is important to resist the temptation to continue wearing the lenses past their prescribed period (often two or four weeks) even if they feel comfortable and the vision is good because the money saved could be at the risk of contact lens-induced complications. Likewise, when you are down to your last one or two months supply, that is an excellent time to order your next set of lenses or, if the prescription is expiring, to be scheduled for an eye examination. The most common noncompliance with discarding lenses occurs with individuals prescribed two week replacement lenses.⁽¹⁾ An easy solution is to replace the lenses on the 1st and 15th of every month.
Why replace the lenses as prescribed by your eye care practitioner? Not only has this been found to result in less complications⁽⁵⁾ but, as they are medical devices, for safe and comfortable long-term wear the United States Food and Drug Administration(FDA) has strongly advised that it is important to follow the recommended lens wearing and replacement schedules prescribed by your eye care practitioner.⁽⁶⁾

Ideally, for soft lenses it would be recommended to dispose of the lens after it has been removed if it is only worn occasionally as every time the lens is removed there is potential for contamination. However, at minimum, the lens should be cleaned and disinfected upon removal, keeping the lenses sealed tightly in the case. Repeat the entire cleaning and disinfecting procedure anywhere from weekly ⁽¹⁾ (for hydrogen peroxide based systems ⁽¹⁾ to at least once a month, depending on the manufacturer's recommendation for your care system. Repeat the cleaning and disinfection procedure within 24 hours of wearing the lens.^(2,3) It is also important to be aware of the expiration date of the lenses and dispose of them prior to that date. For rigid gas permeable(GP) lenses, the procedure is different. These lenses can last for several years; therefore, the lens should be stored in a clean, dry case for long-term storage.⁽⁴⁾ When it is desirable to wear the lens, it should first be cleaned and soaked for a minimum of four hours in a GP disinfecting solution. The exception would be if a spare lens or pair of lenses has been provided unopened - and therefore sterile - in solution from the manufacturer.

Unfortunately, many soft lens wearers stretch the recommended replacement schedules recommended by their doctor. Studies show that there is a trend towards a higher rate of contact lens related complications in those patients that are non-compliant with the recommended replacement frequency. ^(1,2) In two separate studies, encompassing about 1500 soft lens wearers, there was a trend toward increased rates of signs and symptoms consistent with potential contact lens complications in those patients that self-reported a replacement frequency longer than that recommended by the manufacturer.

Washing hands before handling lenses and using the prescribed contact lens solutions properly are important to safe contact lens wear. The greatest concern of doctors fitting contact lenses is infection from dangerous organisms. Therefore, to prevent the transfer of germs from hands to lenses during the insertion and removal process, proper hand washing with an antimicrobial soap is advocated. Antimicrobial soaps have been shown to be more effective than non-antimicrobial soaps in reducing the levels of introduced pathogens.⁽¹⁾ Additionally, bacterial reductions with antimicrobial soaps are significantly improved by longer wash times and greater soap volumes.⁽¹⁾ For example, washing hands for a total of 30 seconds using two pumps of foaming soap is more effective than a 15 second wash and one pump.⁽¹⁾ Hands should then be thoroughly rinsed and dried with a lint free towel. Drying the hands is important to avoid water contact with the lenses since this is a risk for infection as well. For example, exposure of contact lenses and contact lens cases to water has been associated with Acanthamoeba keratitis, a corneal infection that is resistant to treatment and cure. ^(2,3,4,5,6) No other oils, lotions, hand creams or gels are recommended to be used on hands prior to handling lenses as these may coat, soil, or contaminate the lens surface.

The most serious complication of contact lens wear is corneal infection, frequently called microbial keratitis, or infectious corneal ulcers. This can occur if the eye gets irritated or scratched and bacteria or other microbes are present which can gain access to and infect the cornea (the clear layer in front of the eye). ⁽¹⁾ Some researchers believe that a scratch on the cornea is not necessary for an infection to develop, depending on the organism. That is, the prolonged presence of certain microbes against the cornea may be enough to cause a serious infection. ⁽²⁾
Microbial keratitis can be a serious and blinding eye condition if left untreated. Bacterial infections are more common than fungal infections, and the rarest infection occurs with some amoebae. Some bacterial infections are extremely rapid and can cause blindness--sometimes within as little as 24 hours if not diagnosed and treated promptly. Symptoms of infection often include severe pain, redness, mucus discharge, and blurred vision, and often affects one eye only. ⁽³⁾ The best way to determine whether your symptoms are due to an infection or a less severe problem is to consult your eye doctor as soon as possible after the onset of symptoms.
In some circumstances, once the infection has been treated, a dense corneal scar remains which limits vision. These patients may require a corneal transplant to restore their vision.

Fortunately, the rate of contact lens related corneal infections (microbial keratitis) is rare. The rate of infection also varies by type of contact lens worn. Out of every 10,000 lens wearers per year, (between one-12) can develop microbial keratitis when wearing rigid gas permeable lenses or soft lenses for daily wear use only, that is, no overnight use. ⁽¹⁾ The lowest rate of infections occurs in patients wearing rigid gas permeable lenses (1.2 in 10,000 wearers per year) and daily disposable soft lenses have the lowest risk of severe infections. ⁽¹⁾ The highest rate of infections occurs in patients that sleep in soft lenses, with an estimated rate of about 20 in 10,000 users per year. ^{(1, 2,3,4)} Fortunately the risk of vision loss is low, with only 0.6 per 10,000 wearers per year experiencing a loss of best corrected vision. ⁽¹⁾
The following types of patients have been shown to have a greater risk for infection: smokers, those with poor storage case hygiene, those that purchase their lenses over the Internet, and newer wearers with less than six months experience in contact lenses. ⁽¹⁾

Yes. It has long been documented that overnight use (extended wear) of contact lenses increases the risk of infection. As published in 1989, with the soft lenses available at that time, the risk of corneal infection was about 21 in 10,000 users of extended wear lenses per year ⁽¹⁾. In a sister study, also published in 1989, there was a highly statistically significant increased risk of corneal infection when soft lenses were slept in compared to removing lenses nightly before sleep (daily wear). ⁽²⁾ Other publications since that time have continually reported an increased risk of corneal infection (microbial keratitis) during extended wear compared to daily wear even though newer lens types and replacement modalities have been introduced. ^(3,4,5) The most recent study encompassing modern lens types, documented about a risk five times higher for overnight use compared to daily wear. ⁽⁵⁾

Unfortunately, newer lens materials made of highly oxygen permeable polymers, termed silicone hydrogel lenses, have not decreased the rates of infection compared to traditional lenses made of polymers with lower oxygen permeability. ^(1,2,3) However, although the rate of corneal infection (microbial keratitis) with silicone hydrogel lenses worn for extended wear (overnight use) is no different than that of lower oxygen permeable lenses worn for extended wear, silicone hydrogel lenses can be worn for a much longer period of time for the same level of risk (30 days of continuous use with silicone hydrogel lenses versus seven days of overnight use for lenses of lower oxygen permeability). ^(1,2,3)
Similarly, daily disposable lenses have not been shown to decrease the overall rate of microbial keratitis compared to reusable lenses. However, daily disposable lenses have reduced the risk of severe microbial keratitis (which results in vision loss) compared to reusable lenses. ⁽¹⁾

In contact lens related corneal infection, the organism most commonly found is Pseudomonas aeruginosa. In fact, this bacteria is overwhelmingly associated with contact lens-related corneal infection compared with all other organisms. In one study, 71 percent of all cases of contact lens related corneal infections were due to Pseudomonas aeruginosa, or alternatively, 55 percent of all cultures found Pseudomonas aeruginosa compared to only about two-six percent other organisms. ⁽¹⁾

Severe cases of microbial keratitis, or corneal ulcers, are more likely to occur secondary to environmental pathogens and in warmer, humid regions. ⁽¹⁾ Environmental organisms as they relate to contact lens related pathogens include gram negative bacteria, Acanthamoeba, fungi, and Nocardia spp. Of such environmental pathogens, Pseudomonas aeruginosa has been recovered most frequently. ⁽¹⁾ Bacterial infections, such as those caused by Pseudomonas, can be extremely rapid and can cause blindness--sometimes within as little as 24 hours --if not diagnosed and treated promptly. ⁽²⁾
Other serious infections can be caused by fungi and protozoa. Fungal infections are often characterized by severe pain, and are much more difficult to diagnose and treat, because they slowly grow within the cornea and are highly resistant to treatment. ⁽²⁾ Acanthamoeba keratitis is a rare but potentially blinding infection of the cornea caused by a free-living amoeba (Acanthamoeba) that is found commonly in the environment, including water (e.g., tap and recreational water), soil, sewage systems, cooling towers, and heating/ventilation/air conditioning (HVAC) systems.

According to the United States Food and Drug Administration (FDA), it is important not to ignore symptoms of eye irritation or infection which can include discomfort, excess tearing or other discharge, unusual sensitivity to light, itching, burning, gritty feelings, unusual redness, blurred vision, swelling, and pain. ⁽¹⁾ You should remove your lenses immediately and keep them off, contact your eye care practitioner immediately, and keep your lenses as your doctor may want to evaluate them. If lenses are being worn overnight, it is always important to check every morning to ensure that the eyes "look good, feel good, and see well." ⁽²⁾ If not, the eye care practitioner should be contacted.
If an eye infection exists, and you wait two days or longer before contacting your eye care practitioner, the ris of experiencing permanent vision loss is more than four times greater. ⁽³⁾ Therefore, it is important to seek treatment immediately when these symptoms are present. ^(4,5) In addition, it is important to always have a pair of glasses to wear when contact lens wear needs to be discontinued. ⁽⁶⁾

It is very difficult for a doctor to determine exactly what the problem is without evaluating the contact lenses as well as the health of the eyes. There can be many possible causes for the problem(s) including deposits on the lens surface, inflamed lids, swelling of the cornea, abrasion (loss of cells or irritation to the outer layer of the cornea), or an eye infection(corneal ulcer). The management of these problems, once diagnosed, varies and could include any one of several types of medications as well as discontinuation of contact lens wear.
It is very important to contact your eye care practitioner when you have symptoms of eye irritation or infection which can include: ⁽¹⁾

• Discomfort
• Excess tearing or other discharge
• Unusual sensitivity to light
• Itching
• Burning
• Gritty feelings
• Unusual redness
• Blurred vision
• Swelling
• Pain

You should:

• Remove your lenses immediately and keep them out
• Immediately contact your eye care practitioner
• Keep your lenses as your doctor may want to evaluate them

If an eye infection exists, and you wait two days or longer before contacting your eye care practitioner, the risk of experiencing permanent vision loss is more than four times greater. ⁽²⁾ Therefore, it is important to seek treatment immediately when these symptoms are present. ^(3,4) In addition, it is important to always have a pair of glasses to wear when contact lens wear needs to be discontinued. ⁽⁴⁾

You should first contact your eye care practitioner for an appointment to assess your contact lenses. Filmy lenses not only make your vision blurry - like you are looking through a car windshield when it is raining - but also can cause inflammation of your upper lids (termed "giant papillary conjunctivitis"), very red eyes, and even lead to an eye infection. ^(1,2) The following five factors are very important in keeping the lenses clean:

• Replace them as recommended by your eye care practitioner (i.e., daily, weekly, every two weeks, monthly, etc.) Wearing them longer than recommended can result in a deposited, uncomfortable lens.⁽¹⁾
• Do not wear them overnight if they were prescribed for daily wear only. This can result in a filmy lens and increase the risk for an eye infection. ^(3,4)
• Both rub and rinse your lenses after you remove them (unless they are disposed of daily) Rubbing in the palm of the hand for five-20 seconds, depending on your contact lens care solution, helps remove debris and bacteria. ^{(56,7,8,9,10,11)} Contact lenses have been found to become up to eight times cleaner when they are rubbed. ⁽¹²⁾ Be sure to rub the left lens as thoroughly as you rub the right lens. ⁽¹³⁾
• # Wash your hands before handling your lenses This helps ensure your lenses will not receive any contaminants from your hands.
• Have you recently starting taking a medication that may be drying out your lenses? Antihistamines, anti-anxiety agents, and oral contraceptives are among some of the medications that can result in dryness. ⁽¹⁴⁾

If you have been very compliant with your lens wear and care, your eye care practitioner can help you in considering another lens material, such as one of the newer silicone-hydrogel lenses for dry eyes, or a rigid gas permeable(GP) lens. Enzymatic (i.e., extra-strength) cleaners can be beneficial if used weekly. ⁽¹⁵⁾ Likewise, rewetting drops can help lubricate the lenses when they feel dry; this is especially important if you use a computer for long periods of time. ⁽¹⁶⁾ The bottom line is that clean lenses minimize the risk of complications while also often resulting in clear, sharp vision.

You can usually wear your contact lenses while you are on topical medications (i.e. "drops"). However, soft lenses can absorb the medication and - especially the preservatives - can result in burning and stinging of the eye and can even discolor the lens. How long to wait after instilling a drop before applying your contact lenses can vary, depending on the medication and preservatives in the drop. The consensus of the medical community suggests drops should be instilled 10 to 20 minutes before application of contact lenses or after they are removed. ^(1,2,3) The same is true for rigid gas permeable(GP) lenses as the lenses may help prevent the drops from being as effective as they need to be. ⁽⁴⁾ Contact lenses should not be applied after putting an ointment in your eyes as the thickness of this medication can film up your lenses. Also keep in mind that some oral medications cause dryness and may result in the need for you to reduce wearing time or even discontinue contact lens wear. These include antihistamines, sleeping pills, diuretics, tranquilizers, oral contraceptives, and medications for duodenal ulcer, digestive problems, and high blood pressure. ^(5,6)

You should have a pair of glasses for several reasons. First, this will allow you to take a break from contact lens wear if your lenses are not feeling comfortable or if your eyes are red or feel dry. ⁽¹⁾ Continuing contact lens wear when experiencing these symptoms may lead to more serious complications that may require you stop lens wear for a longer period of time. Otherwise you may risk experiencing a complication that would result having to temporarily discontinue contact lens wear. ^2, Over wear of your contact lenses makes you more at risk for serious eye infections. ³⁾ If, for whatever reason, you need to stop wearing contact lenses you will greatly benefit from having a pair of glasses.

Contact lens wearers should see their eye doctor at least once per year. ⁽¹⁾ If it is a complicated fitting involving a special lens design or if there has been a history of complications, the eye doctor typically recommends more frequent visits. ⁽¹⁾ Many of the contact lens complications that occur - such as eye inflammation and infection - develop gradually and, if diagnosed early, can likely be managed before resulting in the need to discontinue lens wear. Follow your doctor's recommended schedule.