H20 - Key Facts Relative to Contact lens Wear and Care
Sam Winnegrad, ABOM, NCLEC
Upon completion of this course, participants will be able to:
- Explain the effect of H2O on a contact lens surface
- Describe the tear film
- Explain proper contact lens care
Sam Winnegrad is a master optician who has instructed anatomy and physiology of the eye as well as other various ophthalmic courses for Roane State Community College in Harriman, Tennessee. He has also taught for Highline College's online optician program out of Des Moines, Washington. Sam is a technical speaker for the American Board of Opticianry and National Contact Lens Examiners. Sam holds his master's degree in business administration as well as a bachelors in science - but above all treasures his license to practice opticianry.
This course is approved for one (1) hour of CE credit by the National Contact Lens Examiners - NCLE, Ophthalmic Level 2. Course # CTWJHI113-2
Water is foundational to our very existence. Without it, we perish. Water is of primary importance, from the depths of the deepest oceans to the unassuming, yet incredibly important lacrimal lake that inhabits our lower eyelids. The Earth is composed of approximately 71 percent water; similarly, though differing based on age and gender, our bodies are composed of about 60 percent water. No wonder we are encouraged to drink eight to 12 glasses of water a day! Overall, water is a beneficial source of nourishment and rejuvenation; however, in some forms, it can be detrimental to our health, which can be exacerbated by contact lens wear. While gas-permeable lenses are problematic in water for multiple reasons, including dislodging, soft contact lenses are even more troubling in the water as their matrix permits the absorption of chemicals and dangerous bacteria. The challenge exists in the fact that individuals encounter water daily and in many different forms. How do we instruct our contact lens patients to care for their lenses? When is it advisable for our patients to remove their lenses? What are the risks associated with wearing contact lenses in pools or natural bodies of water? These are some of the many questions we must be able to answer as eyecare professionals. Our duty lies in educating our patients. We can only hope they make the right decisions when faced with opportunities for non-compliance. Unfortunately, it is not enough to only verbally instruct patients on contact lens care and proper wearing habits; steps must also be taken to document these conversations in our patient's electronic medical records (or paper chart if you are still holding on).
As mentioned earlier, approximately 71 percent of the Earth is covered with water, but what exactly is water? In simplest terms, water can be defined as an odorless, tasteless and transparent liquid. It is a compound of hydrogen and oxygen commonly referred to as H2O. By weight, water contains approximately 89 percent oxygen and 11 percent hydrogen. Water freezes at 32 degrees Fahrenheit or 0 degrees Celsius. Water boils at 212 degrees Fahrenheit or 100 degrees Celsius. Water comprises our rain, oceans, rivers and ponds.
The hydrologic cycle, known as the water cycle, describes how water moves throughout our environment. There are seven steps in the water cycle. The first step is evaporation. This is where water becomes vapor as it absorbs heat from the sun. The larger bodies of water, such as oceans, lakes and rivers, provide most of the evaporated water. The next step of the hydrologic cycle is condensation. This occurs when the water that evaporates rises into high altitudes, where it is colder and turns into small particles of ice. These particles will join to create various formations, such as fog and clouds. Sublimation is the third step of the water cycle. This is where ice turns directly into water vapors without ever turning into a liquid. Sublimation is a slower process than evaporation but still contributes to the vapors in our atmosphere. Precipitation is the fourth step of the water cycle. This is where the droplets get too large to maintain suspension in our clouds and turn into precipitation, such as rain, snow or sleet. A change in temperature or wind pattern can usually drive this.
Transpiration is the fifth step of the cycle. This is where the water that precipitates enters the soil and is absorbed by plants and used in the process of photosynthesis. Runoff is the sixth step of the water cycle. It occurs when the water that pours over the surface of the Earth flows into channels that form the rivers and lakes of our hydrosphere. Infiltration is the final step of the hydrologic cycle. Effectively, infiltration is the precipitated water that does not run off or become absorbed by plants through transpiration. This water is absorbed deep down into the soil. Once the soil has reached its maximum level of infiltration, any remainder will turn into runoff.
INTERESTING FACTS ABOUT WATER
Though water surrounds us and enables us to exist, rarely do we stop to contemplate some of the more interesting phenomena related to this liquid. For example, a gallon of water weighs 8.34 pounds. Only one percent of the Earth's water is drinkable. Ninety-seven percent of the water on the Earth is salt water, and two-thirds of the remaining three percent is found in the ice caps and glaciers. Water is naturally both adhesive and cohesive. Adhesion allows the water to stick to other surfaces, while its cohesive properties allow it to stick together to itself. This explains why water forms droplets; the strong hydrogen bonds give water this property. Water is so important that humans cannot survive over a week without it—though this differs from individual to individual depending on their physical health.
THE TEAR FILM
The pre-corneal tear film comprises three distinct layers, each with its purpose and function. They comprise water intermingled with traces of minerals and other soluble additives that nourish and benefit our eyes. The outermost layer of the tear film is called the lipid or oily layer. The Meibomian, Zeis and Mol glands secrete this layer. The purpose of this layer is to prevent the tears from evaporating off the eye's surface. Isn't it interesting to think that the microscopic evaporations of the tear film end up in the clouds of our sky after condensation? The middle layer of the eye is the aqueous layer. This layer comprises the brunt of the tear film and is produced by the lacrimal glands. Its purpose is to provide a moist surface for the eye's anterior and supply vital nutrition. The innermost layer of the tear film is the mucoid, or mucous layer. This layer is secreted by goblet cells of the conjunctiva. As mucous is sticky, it is easy to understand how this layer ensures the tear film adheres to the eyes.
PROPER CONTACT LENS HYGIENE
There are quite a few different types of wear schedules that can be prescribed to your patients. The wear schedule, or modality, defines the length of time one can wear a contact lens. Some typical schedules are daily disposable, two-week and monthly. The advantage to the daily disposable wear schedule is that there is a reduced risk of infection and a decline in care steps as there is no need for cleaning and disinfection—generally, the longer the wear schedule, the greater the risk for infection or complication. Though the daily disposable modality can be considered the healthiest of the options, the cost can be a prohibitive factor for many. Newer technology and rising competition have already enabled the entry price of these lenses to drop. Correct hand washing is one lens health factor that transcends modality and is paramount to proper hygiene.
The Centers for Disease Control (CDC) informs us that following proper handwashing guidelines is the most effective way to reduce infectious disease transmission. There are five steps to washing hands properly. First, wet your hands with running water and then apply soap. The second step is to lather. Notably, one must lather the backs of the hands, between the fingers and under the fingernails. The third step is to scrub vigorously for at least 20 seconds. After scrubbing, the fourth step is to rinse the hands thoroughly. The final step is to dry off with a clean towel or to allow the hands to air dry. Even the healthiest contact lenses can become compromised if one fails to wash their hands properly.
Soft contact lenses that are not of the daily disposable modality must be stored and disinfected in the proper solution. Nowadays, most solutions are multipurpose compositions. Multipurpose solutions are an all-in-one solution used to clean, store and disinfect lenses. Though most multipurpose brands permit submersion in the solution as an efficacious means to clean the lens, studies have shown that gently rubbing the lens in the solution aids the cleaning process and helps to lift deposition. Saline is not to be confused as a contact lens cleaning solution. Saline is a Ph-balanced saltwater that should only be used to rinse lenses before insertion. The Ph of the tear film is 7.6, and most saline and contact lens solutions will seek to mimic this to encourage corneal acceptance and overall lens comfort.
Simply put, a lake is a body of water surrounded by land that is not a part of an ocean. There are also rivers and other water outlets that serve to supply lakes. There are also two main types of lakes—open and closed. Open lakes allow water to leave through a river or other outlet. As mentioned earlier, a closed lake has no openings, and thus water only leaves through condensation and the hydrologic cycle. Ponds are similar to lakes but are not as large and will generally be closed. Another distinct difference between a pond and a lake is that a pond is shallower and allows plants to live in the water and collect sunlight.
Should your contact lens-wearing patients swim in lakes with their contact lenses? Most eyecare professionals would say, “Definitely not!” Next, we will evaluate some contraindications to wearing contact lenses while enjoying a day in the water. One of the lesser-considered characteristics of water and contact lenses is tonicity. Above, we mentioned that contact lens solutions seek to match the tonicity of the tear film, but bodies of water are not as friendly. Ponds and lakes are generally hypotonic, meaning that there is a low concentration of solutes in the water—this gives lakes a lower osmotic pressure. Lake water will penetrate the contact lens matrix and increase the overall diameter of the lens. We know that as lens diameter increases, the lenses will fit tighter. This can be of particular interest, as patients are more likely to damage their corneas during lens removal if they are not carefully removing the tighter-fitting lens. If your patients decide to swim in their lenses, they should use some form of rewetting drop before lens removal to aid in the process.
Interestingly, ocean water is a hypertonic solution. This means that the solute (i.e., salt) is greater than the solvent (i.e., water). This is important because water is attracted to solutions with a higher solute concentration. This is why when people wear their contact lenses in the ocean, they may become looser as the lens diameter shrinks.
Bacterial infection is also another concern of swimming in contact lenses. Wearing lenses increases the risk of infection as the corneal epithelium is under increased stress. Lakes can breed many microorganisms, such as staphylococci, streptococci, pseudomonas aeruginosa and acanthamoeba. The most infamous and sight threatening of these are pseudomonas and acanthamoeba.
Whether above the ground, underground or an inexpensive inflatable variation, pools can be detrimental to contact lens wearers. The temptation can be great to leave the lenses in, but this does not come without risk. A swimming pool can be defined as "an artificial pool for swimming in." Though artificial, the hazards can be all too real. Various chemicals are used in swimming pool maintenance to combat microbes and other contaminants. The most common of these chemicals is the element chlorine, usually in the form of calcium hypochlorite. One common condition related to swimming in contact lenses is called chlorine burn. This is where the epithelial anterior surface of the cornea becomes damaged. The patient may experience a burning sensation, be light sensitive and may even experience blurry vision. Also common with this condition is corneal edema, which is swelling. Severe enough cases of chlorine burn will cause marked differences in keratometry mires. While swimming pools may seem harmless enough due to their regular maintenance, the risks are still grave. As with ponds, swimming pools are hypotonic and will cause lenses to fit tight. There is also a risk of microbial contamination and even chemical burns from calcium hypochlorite or other maintenance chemicals.
BATHS AND HOT TUBS
Emmetropic individuals, who can view objects at infinity in sharp focus with the lens in a relaxed state, have no idea how fortunate they are not to have to "deal with" the annoyance of fumbling around while attempting to bathe. Most individuals enjoy their bath water on the hotter side. The ideal water temperature for a bath is 100.6 degrees Fahrenheit (2 degrees warmer than the human body temperature). Water that is hotter than 102.0 degrees can harm one's health. The average hot tub temperature is also in the 100 to 102 degree Fahrenheit range; however, many hot tub manufacturers list 104.0 degrees as the maximum temperature. Hot tubs have many risks associated with them. Even though the water is more than likely chlorinated, chlorine begins to lose effectiveness when the water temperature rises above 84 degrees Fahrenheit. Some common health risks associated with baths and hot tubs are pseudomonas infection, mycobacterium avium (related to tuberculosis), herpes, Legionnaire's disease and an increased risk of congenital disabilities for pregnant women.
It is always recommended for one to remove their contact lenses before entering a bath or hot tub. Soft contact lenses are notorious for absorbing the world around them, including any water that may come in contact with the eyes. Most bath water will make lenses change their shape. Instead of fitting correctly, the lenses generally increase in diameter and adhere to the eye. Not only does the non-sterile water prove dangerous, as the risk of infection increases, but changing the shape of the lenses makes removal more difficult, which can easily lead to corneal abrasion or erosion during removal. Thriving microscopic bacteria, if given the chance, will latch onto the contact lens matrix and work its way into the cornea. If lenses are inadvertently worn while bathing, they are recommended to be removed as soon as possible. Affected lenses must be thoroughly disinfected. A multipurpose solution may be used, but a hydrogen peroxide-based solution may prove more efficacious.
The term "tap water" is commonly used, but how do we define tap water? Tap water is any water that comes from a piped supply, i.e., water derived from the house's plumbing system. Tap water is a homogenous mixture of water (H2O), trace minerals and electrolytes. Some trace minerals in common tap water are sodium, magnesium, potassium and calcium. Unlike the solutions and saline manufactured for contact lens wear and care, tap water is not sterile. Regulations still permit some microorganisms to live within tap water, disinfectants, and organic and inorganic chemicals. What is deemed safe for ingestion is not necessarily safe for interaction with the eye. This is only exacerbated with contact lens wear. Patients must be educated on the dangers and differences between tap water and multipurpose solution. What seems evident to eyecare professionals may not be so apparent to the average health care consumer. First, patients must understand that tap water has no disinfecting properties. It does not serve to clean lenses. Secondly and more dangerous is the fact that tap water may harbor extremely serious bacteria and microorganisms that will latch onto contact lenses and potentially infect the eye. Lastly, storing contact lenses in tap water will entirely disrupt the pH of the tear film upon insertion. The mean human tear film pH is 7.6, whereas the average tap water's pH can range from 6.5 to 8.5; a pH significantly dissimilar from the tear film will make lens acceptance quite difficult.
Have you ever seen someone insert a contact lens inside their mouth as some sort of a "safe haven" or to re-moisten their lens? Not only is this gross, but it is also quite risky behavior. Saliva is made up of 99.5 percent water—it is the other 0.5 percent that can be concerning. Other elements found in saliva include sodium, potassium, calcium, proteins, enzymes, urea, ammonia and potentially dangerous bacteria. It is always a good idea for patients to carry a small bottle of multipurpose solution on them so they are not tempted to use saliva to care for their lenses.
An acanthamoeba is a type of protozoan, defined as a single-cell living organism. Acanthamoebas are microscopic and are often found in soil, air and bodies of water such as rivers, lakes and oceans. Contact lens wearers are especially susceptible to the sight-threatening condition acanthamoeba keratitis, which occurs when these free-living protozoans attack the cornea. According to the CDC, 85 percent of patients who develop acanthamoeba keratitis are contact lens wearers. Most of these cases could be avoided if individuals removed their lenses before entering bodies of water. Other risk factors contributing to AK (acanthamoeba keratitis) are improper hygiene and lens care techniques, especially not adequately disinfecting lenses. Some common symptoms associated with AK include pain, tearing, redness, foreign body sensation, and even temporary and permanent vision loss. Unfortunately, due to the rare nature of this condition, diagnosis and treatment can be difficult. Patients may have active pseudomonas as well as dormant. The active form of these protozoans is referred to as trophozoites and generally responds well to topical treatment using cationic antiseptics and diamidines. The dormant variant manifests as a cyst and is more challenging to treat. In rare instances, a surgical procedure is necessary. Patients are generally monitored for long periods to ensure eradication and no recurring issues.
Pseudomonas aeruginosa is a prevalent pathogen that will attack the human body if given the opportunity. It is one of the most commonly treated bacteria. Pseudomonas gravitate to all forms of water. They can be found everywhere, from lakes and oceans to swimming pools and tap water. Incidences as innocuous as improperly drying one's hands before inserting a contact lens can lead to an infection. Pseudomonas aeruginosa will latch onto contact lenses if given the opportunity. Pseudomonas keratitis occurs when these pathogens invade the cornea, causing all sorts of trouble including but not limited to pain, light sensitivity (photophobia), conjunctivitis, edema and discharge. Clinically, pseudomonas keratitis may present with corneal ulceration, edema and a thick yellow or green discharge. Patients may also present with ring formations in their corneal endothelium or inflammation of the anterior chamber under biomicroscopy. Treatment of pseudomonas bacteria will usually involve topical and fortified antibiotics. One of the greatest threats is to manage and thwart the development of any sight-threatening ulcers. Systemic antibiotics may be prescribed if the pseudomonas is thought to have invaded the sclera, or if perforation of the cornea is a concern. As with all corneal infections, precautions such as practicing proper hygiene and not exposing contact lenses to water can help prevent contamination. Daily disposable contact lenses are also becoming a rapidly growing option, minimizing the need for lens care solutions and helping patients to remain compliant and healthy!
Water is innately involved in all aspects of our existence—our grand inhabitation, the Earth, comprises 71 percent water. Water is one of the most significant and fundamental requirements for life. Therefore, we are not to be surprised that many harmful and unwelcome guests may live in the water we come into contact with daily. Microorganisms and other organic and inorganic nuisances flourish in the water that surrounds us. The danger of water is that its clarity must not be mistaken for purity. A wealth of infiltrates can be observed in water under microscopic observation.
We must educate our patients on contact lens wear and care related to water. Misinformation, or a lack of education, is too prevalent with contact lens wearers. Obvious points of importance (i.e., tap water is not the same as sterile saline solution) must be communicated to patients, as we cannot make broad assumptions. Insertion and removal training is the perfect opportunity to share contact lens best practices, such as not swimming in lenses. While considering our patients' education, we must not assume that because someone is a "seasoned" contact lens wearer, they have already received and retained proper instruction. While educating your patients, do not ask "yes or no" type questions. Instead, make statements such as, "Tell me how you clean your lenses." Keeping your patients healthy is your number one concern. A myriad of prescription swim goggles options are available for your patients with higher prescriptions that may genuinely need correction in water. LASIK and other refractive surgeries may also be an option but come with risks requiring physician and patient assessment.