What are extended wear contact lenses?

There are risks and benefits for those wearing extended wear lenses. For instance, one British study has found that those who wear extended wear lenses are actually at less risk of developing serious cases keratitis. However, the same survey suggested that the risk of developing moderate keratitis was elevated by wearing continuous wear lenses. The study also suggested that the risk of developing keratitis was higher in those patients who wore their lenses overnight.

In America, extended wear lenses have been deemed safe to wear since 1981. However, the FDA recommended that they be worn for no more than 2 weeks at a time. This was then superseded by a ruling which found that 30 day periods were also acceptable. Subsequent studies then suggested that the ruling had led to a spike in eye infections amongst extended wear lens users. Hence the FDA reduced the recommended period to 7 days.

At the time, advocates of opticians and doctors argued that overnight lens wearing carried unacceptable risks, and issued advice to patients that wearing lenses overnight be avoided. Their major worry related to the risk of bacterial infection, suggesting that closed eyelids in warm environments were ideal spaces for bacteria to thrive. Additionally, it was felt that the lower oxygen levels overnight compromised the body's ability to fight infections.

These infections can include manageable conditions like pink eye, as well as far more serious problems such as Acanthamoeba Keratitis or nasty fungal infections. These can lead to seriously impaired vision or even permanent loss of eyesight if not treated. It is known that extended wear of contact lenses raises the risk of contracting these infections.

Using extended wear contact lenses can lead to immediate symptoms such as dry eyes, irritation and redness, which leads to intense discomfort. In some cases, this is due to the eyes adapting to continuous lens wearing, or they could develop due to a new lens care schedule and different cleaning solutions. It is also important to remember that there is no firm data to suggest that patients can develop allergic reactions to extended wear lenses.

However, if you wear products containing silicone hydrogel for extended periods, this can cause dryness of the eyes and anyone prone to dry eyes can find such lenses extremely uncomfortable. Thankfully there are next generation lens cleaning products that can counter this situation by maintaining a high level of moisture around the lens.

Many of those who use extended wear contact lenses report a higher degree of sensitivity when they switch to the new lenses. This is partly because of the rush of oxygen to the cornea that permeable extended wear lenses allows. Conventional lenses are much less permeable, resulting in a smaller amount of oxygen reaching the eye. In turn, this can make it harder to "feel" the lens, so when more oxygen is allowed through, sensitivity can result. This greater sensitivity is well documented, and is nothing to cause concern. Instead, it is a sign of more oxygen reaching parts of the eye that need it, and may indicate improved eye health.

Recent years have seen huge advances in the technology behind extended wear lenses. This has resulted in vast improvements in safety and efficacy, rendering extended wear lenses suitable for increasing numbers of people. Despite this, opticians and doctors often advise patients to avoid extended wear lenses due to the perceived risk of infections.

One of the major advances in the field has been the development of silicone hydrogel lenses. These lenses were specifically designed to combat the dangers of hypoxia (lack of oxygen) reaching the eye, which could lead to blurring of vision and irritation, as well as raising the risk of eye infections. These lenses are disposable varieties, and represent the majority of the market, being worn for a couple of weeks or one month before being replaced with a fresh set of lenses.

All lenses are prone to accumulating particles of lipids, protein or other dirt that can lead to inflammation of the eye. And these substances can also heighten the risk of infection.

Another recent advance has been the development of extended wear gas permeable lenses. These have been welcomed by some opticians and doctors as a safer way to wear lenses continuously. This is because they can move around the eye when the wearer blinks, reducing the accumulation of dirt and pathogens in the space between the eye and the lens surface.

Another thing that eye experts tend to recommend is that anyone considering wearing lenses continuously adopts a flexible schedule. In this case, opticians may recommend that patients limit the number of nights when they leave their contact lenses in, saving them for special occasions, while usually removing them before sleeping.

Despite technological development, continuous lens wearing still carries with it some risks. Opticians believe that these risks still make extended wear lenses less desirable than daily wear varieties.

In fact, a 2010 study found that opticians have become less willing to prescribe extended wear lenses. Researchers in 39 nations recorded prescriptions over 14 years, finding that 2006 saw a peak in the prescription of extended wear lenses. In 2006, around 12 percent of prescriptions were for extended wear. By 2010, this had fallen to nearly 8 percent. However, national variations do exist. In Norway, a massive 27 percent of prescriptions are for continuous wear. In America, it is only 10 percent.

It is not clear why extended wear lenses have become less popular. However, one factor may be the rise of daily disposable lenses, which are more convenient for some people than extended wear lenses, requiring very little maintenance and offering excellent vision. Another factor may well be that extended wear lens patients are instead opting to undergo laser eye surgery. This would eliminate entirely the need for contact lenses or glasses.

Whatever type of lens you wear, excellent hygiene is vital in warding off infections and ensuring that eyes remain healthy. Indeed, most infections related to lens wearing are caused by poor lens hygiene, and lenses should be cleaned thoroughly after every use. In the case of extended wear lenses, infection can be avoided by ensuring that you do not wear them beyond the recommended limit.

This kind of contact lens can be prescribed with a weekly, fortnightly or monthly schedule. Opticians also suggest that on at least one night in every week, they are not work while sleeping. It is also not advisable to wear these lenses while taking a swim or enjoying a hot tub, as well as steamy or smoky environments such as a sauna.

Whenever irritation or redness results from wearing extended wear contact lenses, and whenever your vision is impaired, try a fresh pair of lenses. If your vision is not improved, the lenses should be discarded and you may need to consult your optician to devise an alternative lens wearing strategy.