Advanced Studies in Contact Lens Care and Ocular Health
Roy S. Chuck, MD, PhD,* and Elliott H. Myrowitz, OD, MPH
This issue of Johns Hopkins Advanced Studies in Ophthalmology addresses several important aspects of contact lens wear and care with the eye care professional in mind. To meet the optometrist's need for current information and to underscore the important role of all eye care professionals in contact lens care and ocular health, this publication draws on the expertise of 3 optometrists, an ophthalmologist, and a chemist who is a consultant to the contact lens industry. This viewpoint is especially germane because, according to data from the American Optometric Association (AOA), optometrists provide more than 66% of primary eye care services in the United States1 and because more than 80% of the estimated 36 million Americans who wear contact lenses go to an optometrist for their eye care.1,2
A good starting point is to review the demographics of contact lens wear in the United States and the different types of contact lenses that are approved for use. Data from the AOA indicate that approximately 87% of Americans who wear contact lenses wear soft hydrogel lenses; the remaining 13% wear rigid lenses with varying degrees of oxygen permeability.1 AOA statistics also indicate that most contact lens wearers are nearsighted, approximately 66% are female, 10% are aged 18 or younger, and 65% are between the ages of 18 and 44.2 Approximately 80% wear daily wear soft lenses, over 50% wear 1- to 2-week disposable lenses, and 15% wear extended-wear (up to 30 days) soft lenses.2
All contact lenses are medical devices that are regulated by the US Food and Drug Administration (FDA), and solutions used to clean and disinfect contact lenses are subject to US FDA regulation as well.3 The materials used to manufacture traditional soft hydrogel lenses are classified by the US FDA into 4 groups on the basis of their water content and whether they are ionic.1 Although the hydrogel materials are believed to exhibit the same chemical behavior, the oxygen permeability of traditional hydrogel materials across all groups increases with the water content.1
Specifically, hydrogel materials in group I have a low water content and are nonionic; those in group II are also nonionic, but have a high water content. Materials in groups III and IV are ionic, with those in group III having a low water content and those in group IV having a high water content.
Silicone hydrogel lenses, which are made of silicone to enhance oxygen permeability and traditional hydrogel materials to enhance comfort, represent a newer class of hydrogel lenses.1,3 These lenses can be worn on a daily basis and some continuously for up to 30 days.3 They account for nearly 50% of all new lens fittings, particularly for overnight and extended wear,3,4 and are an alternative to laser surgery to correct refractive errors.3
In addition, some contact lens manufacturers have introduced a second generation of silicone hydrogel lenses offering enhanced comfort in dry environments, such as airplane cabins and air-conditioned offices.3
With the increasing use of soft and silicone hydrogel lenses in mind, Jason J. Nichols, OD, MPH, PhD, reviews the key functions of lens care solutions and explains how these functions are interrelated. He discusses the importance of lens comfort, the role of the tear film in protein and lipid deposition, and the efficacy of multipurpose and hydrogen peroxide solutions in cleaning and disinfection. He also addresses the importance of compliance with lens care regimens.
In contrast, Charlotte Joslin, OD, FAAO, PhD Candidate, focuses on microbial keratitis, the lens-related complication of greatest concern to patients and eye care professionals. She explains the role of a stable tear film and the corneal epithelium as a barrier against infection, identifies risk factors for corneal staining, and reviews findings from reports of microbial keratitis outbreaks that were associated with 2 specific lens care solutions that have since been taken off the market. She also addresses the critical role of compliance with lens care regimens in preventing infection.
An expert question and answer session devoted to contact lens-related issues that eye care professionals frequently encounter in clinical practice provides some additional insights on lens care and ocular health.
The material presented in this issue of Johns Hopkins Advanced Studies in Ophthalmology provides ophthalmologists and optometrists with a deeper understanding of contact lenses and lens care solutions, in addition to strategies to prevent infection and other complications associated with contact lenses. This information, when integrated into patient counseling directed at enhancing compliance with lens care regimens, should result in increased patient comfort and fewer lens-related complications.
1. Optometric Clinical Practice Guideline. American Optometric Association. 2nd ed. 2006. Available at: http://aoa.org. Accessed March 26, 2008.
2. Facts and Stats. American Optometric Association Web site. Available at: http://aoa.org/x5231.xml. Accessed March 9, 2008.
3. Contact Lens Council Web site. Available at: http://www. mycontactlenses.org. Accessed March 15, 2008.
4. Key JE. Development of contact lenses and their worldwide use. Eye Contact Lens. 2007;33:343-345.
*Tom Clancy Professor of Ophthalmology, Director of Refractive Surgery, The Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore, Maryland.
Assistant Professor of Ophthalmology, Chief of Optometric Services, The Wilmer Eye Institute at Green Spring Station, The Johns Hopkins Medical Institutions, Lutherville, Maryland.
Address correspondence to: Elliott H. Myrowitz, OD, MPH, Assistant Professor of Ophthalmology, Chief of Optometric Services, The Wilmer Eye Institute at Green Spring Station, The Johns Hopkins Medical Institutions, 10753 Falls Road, Suite 455, Lutherville, MD 21093.
The content in this monograph was developed with the assistance of a staff medical writer. Each author had final approval of his/her article and all its contents.