Almost thirteen percent of people who have visual correction needs have turned to contact lenses. Over the years, many technological advancements have been introduced by the contact lens industry that have changed the way lenses are made, what they are made of, as well as the way they are packaged for consumption by wearers. The one thing that hasn’t changed however, is that contact lenses are still medical devices and this means that you should be fitted by a eye care professional and follow their lens care instructions thereafter. Wearing contact lenses is a serious matter. A prescription is required to wear them. As with any prescription you receive, it requires your understanding of the potential problems that you could experience as a result of non-compliance and over wear.
When disposable contact lenses were first introduced in the early 1990’s, many eye care professionals applauded, as the most frequent problems they encountered as practitioners were related to lens handling and care. The seemingly perfect solution was provided when the lens industry introduced daily disposable contact lenses. These lenses were designed and packaged for daily replacement; that is daily use, removal, and disposal each and every day contact lenses are worn. These lenses solved many problems. With these lenses now, there is no need to have lens cases for their storage as the lenses are to be discarded at the end of the day. No lens case means that there is no risk of transmitting bacterial flora from a dirty lens case to the lens. Fresh and sterile lenses are inserted each day. No need for extensive cleaning and disinfecting. What could be more convenient?
Even though an eye care professional provides clear instructions regarding the wearing regimen and its importance, the greatest challenge remaining with the fitting of daily disposable contact lenses is over wear. This is an event that happens when the wearer tries to use the same daily wear contact lens for more than one day. In this specific instance to do so will re-introduce the lens case and the solutions parameters with their related issues. More importantly however is the fact that patients tend not to clean their daily wear lenses when using them multiple times. Doing so takes us right back to issues that pertain to the basics of dirty lenses and their problems.
To make the point on the specific issue of how dirty lenses can affect ocular health we need to review some basic information on the eye. The tissue on which your contact lenses sit when properly fitted is called the cornea. It is a very thin and clear tissue that represents the outer layers of the eye, layers of tissue that function to transmit and help focus light rays traveling into the eye. The cornea requires oxygen to remain healthy; yet, it has no blood vessels. This seems almost impossible but it is in fact the reality of the cornea. It has no direct internal supply of oxygen. Therefore, the cornea must rely on outside or atmospheric oxygen to remain healthy. To accommodate this phenomenon contact lenses are made from various porous materials. These pores, created by the gaps in the interlacing of the various types of plastic polymers, allow oxygen to be transmitted through the contact lens to reach the cornea. Oxygen diffused through tears is also important but it is less contributory than that which comes from the atmosphere.
Each time you place a contact lens on your eye, tears immediately begin to coat the lens. Human tears are necessary to keep the eye moist, clean, and clear. Tears contain lipids and more than 50 different proteins. These lipids and proteins immediately begin to fill the porous surface of the contact lens, the same pores that were originally designed to allow for the oxygenation of the cornea. When wearing the same lens over and over again what you will see happening is that the pores of the contact lens begin to clog up with natural tear components. Over time, this process will decrease and eventually severely limit the transmission of oxygen to the cornea. When looking at the lenses at the end of a day’s wear, one can see that the lens is coated with debris and will require some physical rubbing to dislodge this debris. Once rinsed the debris will have been decreased on the surface but with little to no effect on the debris lodged in the pores.
When you compound the issues of lens cleanliness, and lens soiling with the ever important issue of oxygen deprivation you truly begin to comprehend the reasons for staying with a properly executed daily wear regimen. Any time the cornea is deprived of oxygen it sends out distress signals to the body for help. The body can do several things. One of these is to signal the blood vessels that exist at the periphery of the cornea to begin to move into the cornea as an emergency measure to supply oxygen. Since the cornea is always clear and without blood vessels, this condition could become a pathological one and, if allowed to develop, may bring blood vessels right into your field of vision.
So as you can see, keeping lenses clean and fresh is high on eye care practitioners’ list of priorities. Limiting the re-use of your daily disposable lenses to a one-time use only as designed, provides both the professional and the contact lens wearer with a great measure of safety and ocular health, factors which were the basic objectives leading to the development of the daily wear lens. Encouraging successful fitting and the ongoing use of the wearer’s contact lenses is the only way that the contact lens industry can continue to count on providing a valuable service to its clients.