Spotlight on Science
PROTEIN DEPOSITION: PERCEPTION VS. REALITY
NEW EVIDENCE MAKES US RETHINK DEPOSITION AND ITS CLINICAL RELEVANCE IN OUR EVERYDAY PRACTICE
David Ruston, F.C.Optom, Dip.C.L.P., F.A.A.O.
NO SINGLE LENS MATERIAL or design will suit every patient. Ocular physiology, patients’ lifestyle needs and clinical signs and symptoms all play significant roles in contact lens selection.
For many practitioners, tried and true hydrogel materials, such as etafilcon A, are still a great option for their daily disposable patients.
Now new evidence is coming in about how beneficial proteins like lysozyme§ interact with some of these materials, such as etafilcon A and other group IV hydrogels, and may help explain why these materials have stood the test of time.1
THE ROLE OF LYSOZYME
Lysozyme, a protein produced by the lacrimal gland, is the most common protein deposited on contact lenses. It is present in tears in large quantities, accounting for approximately 40% of all of the proteins found in the tear film.2,3
In its native state, this positively-charged protein works as part of the eye’s natural defense mechanism. But, when a contact lens is placed on the eye, the structural integrity of lysozyme can be compromised, causing it to change its structure and lose its function. This alteration to the protein is referred to as denaturation.
Denatured lysozyme has been linked to immunological responses through in vitro studies. Recently, through research done at the Center for Contact Lens Research at the University of Waterloo by Professor Lyndon Jones and his team using cultured human corneal epithelial cells, it has been shown that the denatured protein lysozyme also triggers the release of inflammatory biomarkers.§4 This might be one reason why some contact lenses lead to irritation and, subsequently, to uncomfortable wear.
THE VALUE OF ACTIVE LYSOZYME FOR SUCCESSFUL CONTACT LENS WEAR
The challenge with lens wear is not keeping lysozyme out — it is keeping it in its native state. In fact, it is well documented in a number of studies that lysozyme is beneficial in the tear film and is part of the eye’s innate defense system.5,6
Lysozyme is a small, positively charged protein that tends to be attracted in very high quantities to negatively charged high water content ionic (group IV) materials like etafilcon A.
A KEY TO HIGH PERFORMANCE
In fact, the chemistry of etafilcon A allows for the majority of lysozyme to penetrate into the bulk of the lens where it stays in its natural form and does not undergo structural changes.7,8 This means that for 1-DAY ACUVUE MOIST wearers, lysozyme may not be the enemy. In fact, the ability of etafilcon A to help keep this protein in its natural state may be a contributing factor to the high performance of the lens.
MORE KNOWLEDGE
With more knowledge about etafilcon A and its interaction with lysozyme, we can continue to rely on it as an excellent choice for discomfort-prone patients — spherical, astigmatic, and presbyopic — who would benefit from a lens that helps keep moisture in and irritation out. OM
REFERENCES
1. Omali NB, Subbaraman LN, Coles-Brennan C, Fadli Z, Jones LW. Biological and Clinical Implications of Lysozyme Deposition on Soft Contact Lenses. Optometry and Vision Science, Vol. 92, No. 7, July 2015.
2. Leahy CD et al. Initial in vivo tear protein deposition on individual hydrogel contact lenses. Optom Vis Sci 1990: 67: 7: 504-511.
3. Zhao Z et al. Proteomic analysis of protein deposits on worn daily wear silicone hydrogel contact lenses. Mol Vis 2008: 14: 2016-2024.
4. McCanna D, Oh S, Seo J et al. Effect of denatured lysozyme on human corneal epithelial cells. IOVS 2015; 56:ARVO E-abstract 3511.
5. Fleming A. On a remarkable bacteriolytic element found in tissues and secretions. Proc Roy Soc 1922; 43:306Y17.
6. Leitch EC, Willcox MD. Lactoferrin increases the susceptibility of S. epidermidis biofilms to lysozyme and vancomycin. Curr Eye Res 1999;19:12Y9.
7. Okada E, Matsuda T, Yokoyama T, Okuda K. Lysozyme penetration in group IV soft contact lenses. Eye Contact Lens 2006;32:174Y7.
8. Jones L, Senchyna M, Glasier MA, Schickler J, Forbes I, Louie D, May C. Lysozyme and lipid deposition on silicone hydrogel contact lens materials. Eye Contact Lens 2003;29:S75Y9.
§Data on file, 2014. Based on in-vitro data; clinical studies have not been done directly linking differences in lysozyme profile with specific clinical benefits
†Helps protect against transmission of harmful UV radiation through the cornea and into the eye.
*WARNING: UV-absorbing contact lenses are NOT substitutes for protective UV-absorbing eyewear, such as UV-absorbing goggles or sunglasses, because they do not completely cover the eye and surrounding area. You should continue to use UV-absorbing eyewear as directed. NOTE: Long-term exposure to UV radiation is one of the risk factors associated with cataracts. Exposure is based on a number of factors such as environmental conditions (altitude, geography, cloud cover) and personal factors (extent and nature of outdoor activities). UV-blocking contact lenses help provide protection against harmful UV radiation. However, clinical studies have not yet been done to demonstrate that wearing UV-blocking contact lenses reduces the risk of developing cataracts or other ocular disorders. Consult your eye care practitioner for more information.
See page 4 for more important prescribing information.
Practitioner Experience
A Q&A with Dr. Charles Clayton, O.D., about how he incorporates 1-DAY ACUVUE MOIST Brand Contact Lenses into his practice.
A DIVERSE PATIENT BASE
Q: WITH SO MANY LENSES TO CHOOSE FROM, WHAT IS THE ROLE OF 1-DAY ACUVUE MOIST BRAND IN YOUR PRACTICE?
Charles Clayton, OD: I can count on 1-DAY ACUVUE MOIST for all my patients that need a lens for their discomfort-prone eyes and that blocks at least 97% UVB and 81% UVA.†*
The platform also makes it easy for me to fit a wide range of patients — even if the patient has astigmatism or presbyopia.
ADDRESSING CHALLENGES
Q: HOW DOES THE LENS HELP YOU ADDRESS CONTACT LENS COMFORT CHALLENGES, SUCH AS FEELINGS OF DRYNESS AND IRRITATION?
Dr. Clayton: With this lens, the PVP wetting agent is locked into the lens using LACREON Technology — it’s not transient. The moisture lasts, which gives you high success from morning to night. The lens also features an INFINITY EDGE design that helps minimize mechanical irritation throughout the day.
EFFECTS OF LYSOZYME
Q: WHAT IS YOUR OPINION ON THE EFFECTS OF LYSOZYME ON THE ETAFILCON A MATERIAL?
Dr. Clayton: Much like fats, proteins have a bad reputation. But as with fat, there are good forms and bad forms. Lysozyme plays a positive role in the tear film. As long as it doesn’t break down, it’s beneficial, and another reason I choose the 1-DAY ACUVUE MOIST Brand.
RELAYING BENEFITS TO PATIENTS
Q: HOW DO YOU RELAY THOSE BENEFITS TO PATIENTS?
Dr. Clayton: Some patients want a technical explanation and others don’t. Generally, I explain that 1-DAY ACUVUE MOIST is a gentle lens that helps keep some of the good components of the tear film in their happy, natural form§ and it has built-in moisture from morning to night.
| CHARLES CLAYTON, O.D., is in private practice at Bellevue Vision Clinic in Bellevue, WA. He received compensation from Johnson & Johnson Vision Care, Inc. for his time spent for this article. |
| DAVID RUSTON, F.C.OPTOM, DIP.C.L.P., F.A.A.O., is director, Global Professional Affairs for Johnson & Johnson Vision Care Companies in London, UK. Visit tinyurl.com/OMcomment to comment on this article. |
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