Changing History … One Contact Lens at a Time
CONTACT LENS MANAGEMENT TRENDS 2010
Changing History … One Contact Lens at a Time
An update on optometry's quest for contact lens comfort and success
By Arthur Epstein, OD, FAAO
Contact lenses are incredible, life-changing devices. Using contact lenses, I've taken people who were barely functional, virtually unable to see, and I've restored their sight and changed their lives for the better in an instant. I'm sure many of you have had similar experiences. I've seen tears of joy and sadness and every emotion in between. Contact lenses are amazing devices. But where did this all begin? Let me share some of the history and discuss how history has led to this moment of opportunity.
FROM DA VINCI TO WICHTERLE
The contact lens was conceived during the Renaissance, when Leonardo da Vinci sketched the device as early as 1508. In 1888, a German physician named Adolf Fick, who had keratoconus, changed his own life by fitting himself with a rigid contact lens. Polymethyl methacrylate (PMMA) acrylic lenses were invented in the 1930s. In the 1960s, contact lenses made of polymacon (HEMA) were created by Otto Wichterle, a visionary who changed our world. Wichterle, beyond being a brilliant scientist, was able to see the purpose of his invention and quickly developed early hydrophylic lenses.
In 1971, the first soft lens was cleared by the U.S. Food and Drug Administration (FDA), and that's where the journey began for many of us. Thousands of patients turned into millions—all people whose lives were changed by the contact lens.
Extended wear was cleared for cosmetic purposes in 1981, again making history. In 1995, the first daily disposable was introduced. And in 1999, the first silicone hydro-gel lenses were introduced in North America.
EVALUATING REASONS FOR CONTACT LENS FAILURE
Despite all of the good they have done and the lives they have changed for the better, contact lenses are medical devices and have always been associated with some risk.1-8 Researchers have extensively investigated why lenses have been associated with adverse events in some patients. Factors include metabolic issues, corneal acidosis, corneal swelling, effects of materials and permeability, lens care and compliance, and adhesion of bacteria to the epithelium.
We have sought improved materials, and more effective contact lens care products. Today, largely because of these efforts, we're experiencing a renaissance in soft contact lenses and care focused on safety and comfort, which for most patients are top priorities. For the contact lens practitioner, safety is essential, but keeping patients successfully wearing lenses comfortably throughout their lives can sometimes pose a challenge.
One of the biggest issues we face is patient dropout. Comfort is a major driving factor, and we're slowly acquiring additional knowledge and expertise on this issue. We've been able to create a positive experience for most of our patients, while recognizing that we can't afford to continue losing one out of every four of them because of discomfort and end-of-day dryness.
We've learned that it is primarily the surface of the lens—not the entire lens—that loses water to dehydration. When this happens during wear, the lens surface might become hydrophobic, resulting in irritation due to friction each time the lid blinks.
Nathan Efron, PhD, presented early research in 1987, determining that while worn, soft lenses equilibrate to the ocular environment but still maintain their water content.9 This dispelled the myth that all lenses dehydrate, making patients uncomfortable during their wearing day, a concept that many of us had been taught.
Physical changes within the material occur on a molecular level and affect the surface of the lens. The energy of the blink and the dryness of the external environment can stress the lens material, causing the polymer units that help bind water to collapse, resulting in the surface of the lens becoming hydrophobic and uncomfortable—even after as little as several hours of wear.
Patients can go from a fully hydrated, well-conditioned lens to a dry, uncomfortable one in just hours, even when wearing a brand new lens. Mobile polymer chains present in hydrophilic materials can experience rapid rearrangement. They facilitate good wettability when fully hydrated, yet permit rapid surface desiccation as polymer chains entangle and form hydrophobic domains after exposure to a dry environment (Figure 1).10
A fully hydrated, conditioned lens, in which mobile polymer chains allow faster rearrangement and good wettability, can experience surface dessication of the lens that causes polymer chains to entangle and form hydrophobic domains within a few hours of wear.10
To help explain this process, I wrote an article with Dr. Ralph Stone. Dr. Stone is the original inventor of many of the contact lens care products we use today. In our paper, we explained that molecules in contact lens materials possess both hydrophilic and hydrophobic elements. Exposure to the air facilitates surface changes, with hydrophobic ends of these molecules aligning with the dry outer surface. The hydrophilic ends align with the wetness of the inside. The clinical result is that the patient experiences discomfort and often discontinues his lens wear.
As said before, every contact lens manufacturer today focuses on both safety and comfort. Likewise, care solution manufacturers are also working to learn how solutions and contact lens materials interact with and enhance the patient experience. Especially with new lens materials, we see an association between sustained surface moisture and enhanced comfort.
Regardless of where in the world we practice, all contact lens fitters share the same desire. That is to meet or exceed the needs of the patients and customers. As technology advances so have contact lens wearers' expectations. Early on, contact lenses were such a miracle of modern science that the first adopters put up with only hours of wear and tremendous discomfort. Wearers seek excellent comfort that lasts late into the day. This supplement presents the views of a global array of experts in the area of contact lens care and practice management. The information it contains is intended to be used today, to help you grow your business and make you more successful. Experience has shown that the best way to create success is by modeling it and by meeting and exceeding the needs and desires of our customers and patients.
VISION FOR THE FUTURE
I believe we will see improved lenses that allow us to better meet wearers' needs, keep them comfortable, improve safety, and allow us to grow our practices and businesses. The industry will hopefully continue to develop lenses and solutions that are compatible. Changing the future of millions of young children may even become possible, as myopia control becomes a real solution for many of them. I hope this walk through the history of contact lenses was helpful for you. CLS
|1. Schein OD, Glynn RJ, Poggio EC, Seddon JM, Kenyon KR. The relative risk of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. A case-control study. Microbial Keratitis Study Group. N Engl J Med. 1989;321(12):773-778.|
2. Poggio EC, Glynn RJ, Schein OD, et al. The incidence of ulcerative kerati-tis among users of daily-wear and extended-wear soft contact lenses. N Engl J Med. 1989;321(12):779-783.
3. Schein OD, Ormerod LD, Barraquer E, et al. Microbiology of contact lens-related keratitis. Cornea. 1989;8(4):281-855.
4. Schein OD, Poggio EC. Ulcerative keratitis in contact lens wearers. Incidence and risk factors. Cornea. 9 Suppl 1:S55-S58; discussion S62-S63.
5. Glynn RJ, Schein OD, Seddon JM, et al. The incidence of ulcerative ker-atitis among aphakic contact lens wearers in New England. Arch Ophthalmol. 1991;109(1):104-107.
6. Buehler PO, Schein OD, Stamler JF, Verdier DD, Katz J. The increased risk of ulcerative keratitis among disposable soft contact lens users. Arch Ophthalmol. 1992;110(11):1555-1558.
7. Schein OD. Assessing the safety of the new 30-night contact lenses. Eye Contact Lens. 2003;29(1 Suppl):S157-S159; discussion S166, S192-S194.
8. Schein OD, McNally JJ, Katz J, et al. The incidence of microbial keratitis among wearers of a 30-day silicone hydrogel extended-wear contact lens. Ophthalmology. 2005;112(12):2172-2179.
9. Efron N, Brennan NA, Bruce AS, Duldig DI, Russo NJ. Dehydration of hydrogel lenses under normal wearing conditions. CLAO J. 1987;13(3):152-156.
10. Epstein A, Stone R. Surface and Polymer Chemistry. The quest for comfort. Review of Cornea and Contact Lens. 2010;147(1):15-19.
Contact Lens Spectrum, Issue: November 2010