Thanks to the existence of contact lenses, it can sometimes be impossible to tell if someone has a visual impairment or not. These lenses can make huge differences to the lives of their wearers, providing a certain level of freedom that traditional glasses are unable to.

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Contact lenses are worn by an estimated 41 million people in the US.

According to the Centers for Disease Control and Prevention (CDC), around 41 million people in the US wear contact lenses.

While they might feel like a relatively modern invention, rigid contact lenses made from plastic were first manufactured in the US between 1938 and 1940. The soft contact lenses currently worn by an estimated 93% of contact lens wearers were first introduced in 1971.

On a personal level, I first started wearing them as a temporary measure when my declining eyesight made playing sports difficult. However, no longer having my vision affected by raindrops and fogging up (along with the boost in self-esteem that came from not wearing glasses) meant that contact lenses quickly became my main method of improving my vision.

But despite their prevalence and the benefits they can provide, many people (myself included) wear contact lenses in a way that can compromise eye health, increasing the risk of damaged corneas and infection from microbes.

This week has marked the second annual Contact Lens Health Week - a week organized by the CDC to increase public awareness and promote healthy wearing and caring of contact lenses. In this Spotlight, we take a brief look at a few of the "do's and don't's" of contact wear. In addition, we will have a look at some of the interesting "can's and can't yet's" of new contact lens innovations.

Healthy habits mean healthy eyes

Although they are similarly effective at improving vision as glasses, contact lens wearers can be more at risk of eye complications than those who use glasses. If wearers do not follow contact lens care instructions properly, they can put themselves at risk of serious eye infections that can lead to blindness.

The CDC have previously reported that between 40-90% of contact lens wearers do not properly follow their contact lens care instructions, which may explain why serious eye infections affect around 1 in 500 contact lens wearers each year.

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Contact lenses should not be exposed to water. Dangerous microbes such as Acanthamoeba can be found in many sources of water, including tap water.

Many people compromise their visual health due to bad habits when it comes to wearing contact lenses. While it is easy to manhandle glasses, contact lenses need to be afforded a greater level of care.

This means washing hands with soap and water and drying them comprehensively before ever touching contact lenses. Doing so prevents the transfer of germs from the hands to the lenses and consequently the eyes.

Exposing the lenses to water should be avoided as water can carry bacteria and other microbes that cause infection. With soft contact lenses, water can also alter the shape of the lens and potentially damage the cornea. As a result, contact lens wearers should remove their lenses before showering, swimming or using hot tubs, as tempting as it may be to keep them in.

One particular germ, an ameba called Acanthamoeba, is typically found in tap water as well as other water sources. If it causes infection (Acanthamoeba keratitis), patients can require a year or more of treatment, and possibly a corneal transplant.

Another bad habit that should be avoided where possible - unless prescribed by a doctor - is sleeping in contact lenses. In addition to making the eyes feel uncomfortable, sleeping in any type of lens increases the wearer's risk of a corneal infection known as microbial keratitis by between four and five times.

Fast facts about keratitis
  • Keratitis is inflammation of the cornea, the clear tissue that covers the pupil and iris
  • Keratitis can be caused by infectious microbes or by minor injuries to the cornea
  • In severe cases, keratitis can permanently damage an individual's vision.

This risk extends to the wearers of contact lenses that are designed to be slept in. Recently, the story of a man who went blind in one eye after sleeping in contact lenses for almost a week has come to the media's attention.

"The kind of contacts I have are called 'Night and Day' contacts," Chad Groeschen explained to USA Today, "and it was my impression you could leave them in for 30 days straight. I figured the less I was messing with my eyes, the better."

While people can opt to use disposable lenses that are designed to be worn daily, many choose to wear lenses that last for longer periods and need to be stored properly when not in use. Unsurprisingly, many eye problems arise from bad habits pertaining to the storing of contact lens and associated products.

Contact lenses need to be kept clean if they are going to be used for multiple days. Lenses should be cleaned using a specific contact lens disinfecting solution and never water or saliva, as should the case that the lenses are stored in when not in use.

The CDC report that fewer than half of contact lens wearers report always cleaning their contact lens cases, and the number of moderate to severe lens-related infection could be halved if case cleaning practices were improved. Contact lens cases should also be replaced at least once every 3 months.

Contact lenses are stored in a purpose-built solution that is recommended by an eye care specialist. Contact lens wearers should stick to the recommended solution as the recommendation will be based upon the wearer's eyes and medical history. Water should never be used, again due to the fact that it can increase the risk of infection.

Old solution in a lens case should never be "topped off" with new solution - instead, only fresh solution should be used. Solution can become contaminated with microbes that cause infections, and simply adding fresh solution to old solution reduces how effective it is at eradicating germs.

Risky contact lens behaviors are common

According to the results of a recent CDC study, these bad behaviors are incredibly prevalent. The Contact Lens Risk Survey was completed by approximately 1,000 contact lens wearers, and around 99% of respondents reported at least one behavior associated with an increased risk of eye infections.

"Good vision contributes to overall wellbeing and independence for people of all ages, so it's important not to cut corners on healthy contact lens wear and care," reports CDC Medical Epidemiologist Dr. Jennifer Cope. "We are finding that many wearers are unclear about how to properly wear and care for contact lenses."

The following figures illustrate how prevalent some risky behaviors were among survey respondents:

  • Napping while wearing contact lenses - 87.1%
  • Showering while wearing contact lenses - 84.9%
  • Not replacing contact lens cases as frequently as recommended - 82.3%
  • Swimming while wearing contact lenses - 61.0%
  • "Topping off" contact lens solution - 55.1%
  • Sleeping in contact lenses overnight - 50.2%.

"Nearly one third of all wearers reported ever having experienced a contact lens-related red or painful eye that required a doctor's visit," the researchers write.

Considering how common contact lenses have become, the figures produced by the CDC's study are significant, illustrating just how important it is that people become more aware of how contact lenses should be used and the impact bad practice can have on health.

Alternative styles and uses of contact lenses

The health problems that can be caused by risky contact lens behaviors may be enough to put some people off wearing them. However, there are a number of other benefits that specific types of contact lenses can provide that no other devices are able to.

Contact lens designs have become more sophisticated over time. While original products may have only been able to correct nearsightedness (myopia) and longsightedness, newer models of lens can be used to treat and monitor additional conditions that affect the eyes.

Orthokeratology, also known as Ortho-K, is a lens fitting procedure that offers a temporary degree of vision correction by changing the curvature of the cornea to improve its ability to focus on objects.

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The benefits of multifocal glasses, with lenses that feature more than one prescription strength, can also be provided by specific forms of contact lenses.

Altering the cornea's curvature is achieved through the use of specially designed rigid contact lenses that are typically worn overnight. Ortho-K lenses are most commonly used to correct myopia.

Some people wear multifocal glasses because they have a condition known as presbyopia, whereby the eye's ability to focus on nearby objects is lost. However, the condition can also be treated with multifocal contact lenses.

There are two main designs for these types of lenses. Alternating vision lenses have two distinct areas for short- and long-distance prescriptions. The pupil alternates between the two different prescriptions as the wearer's gaze shifts up or down.

Simultaneous vision lenses involve the pupil looking through short- and long-distance prescriptions simultaneously. The two prescriptions can either be laid out in alternating concentric rings or blended together across the lens.

Presbyopia is one condition that a "smart lens" being developed by Google and Novartis should hopefully address. Last year, Novartis suggested that the use of technology such as noninvasive sensors and microchips contained within the lens could "provide accommodative vision correction" to restore the eye's ability to focus.

Their smart lens might also provide benefit outside of visual health. Novartis stated that such a lens could provide a continuous measurement of glucose levels in diabetic patients and deliver this information to a mobile device using a wireless connection.

"We are looking forward to working with Google to bring together their advanced technology and our extensive knowledge of biology to meet unmet medical needs," announced Novartis CEO Joseph Jimenez. "This is a key step for us to go beyond the confines of traditional disease management, starting with the eye."

Always follow the recommendations of eye care providers

One of the most frequently repeated recommendations concerning contact lenses is that wearers should always follow the advice of their eye care providers. Unlike glasses, contact lenses are in direct contact with an opening into the human body, and as such there are far more things that could go wrong from a health perspective.

When used correctly, contact lenses can have a transformative effect on the wearer's quality of life. The same can be said for when they are used incorrectly, only for wholly different and more unpleasant reasons.

It does not take much time to wash hands before handling lenses, to remove them before showering or to clean out a storage case properly, and yet by skipping these simple steps, thousands of contact lens wearers are putting their vision at risk. Follow the advice of eye care providers and vision can be protected for years to come.

Previously, Medical News Today reported on a study that suggested wearing contact lenses may alter the microbiome of the eye.