Issue link: https://optometricmanagementsupplements.epubxp.com/i/587112
22 S P E C I A L E D I T I O N 2 0 1 5 • O P T O M E T R I C M A N A G E M E N T . C O M OPTOME TRIC MANAGEMENT FE ATURE NEW EVIDENCE MAKES US RETHINK DEPOSITION AND ITS CLINICAL RELEVANCE IN OUR EVERYDAY PRACTICE PROTEIN DEPOSITION: PERCEPTION VS. REALITY David Ruston, F.C.Optom, Dip.C.L.P., F.A.A.O. N O SINGLE LENS MATERIAL or design will suit every patient. Ocular physiology, patients' lifestyle needs and clini- cal signs and symptoms all play signifcant roles in contact lens selection. For many practitioners, tried and true hydrogel mate- rials, such as etaflcon A, are still a great option for their daily disposable patients. Now new evidence is coming in about how benefcial proteins like lysozyme § interact with some of these materials, such as etaflcon 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 com- mon protein deposited on contact lenses. It is present in tears in large quantities, accounting for approxi- mately 40% of all of the proteins found in the tear flm. 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 lyso- zyme can be compromised, causing it to change its structure and lose its function. Tis alteration to the pro- tein is referred to as denaturation. Denatured lysozyme has been linked to immunological responses through in vitro studies. Recent- ly, through research done at the Center for Contact Lens Research at the University of Waterloo by Pro- fessor Lyndon Jones and his team using cultured human corneal epithe- lial cells, it has been shown that the denatured protein lysozyme also triggers the release of infammatory biomarkers. §4 Tis might be one rea- son why some contact lenses lead to irritation and, subsequently, to un- comfortable wear. THE VALUE OF ACTIVE LYSOZYME FOR SUCCESSFUL CONTACT LENS WEAR Te 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 num- ber of studies that lysozyme is benef- cial in the tear flm and is part of the eye's innate defense system. 5,6 Lysozyme is a small, positively charged protein that tends to be at- tracted in very high quantities to negatively charged high water con- tent ionic (group IV) materials like etaflcon A. A KEY TO HIGH PERFORMANCE In fact, the chemistry of etaflcon A allows for the majority of lyso- zyme to penetrate into the bulk of the lens where it stays in its natural form and does not undergo structural changes. 7,8 Tis means that for 1-DAY ACUVUE MOIST wearers, lysozyme may not be the enemy. In fact, the ability of etaflcon A to help keep this protein in its natural state may be a contributing factor to the high perfor- mance of the lens. MORE KNOWLEDGE With more knowledge about etaflcon A and its interaction with lysozyme, we can continue to rely on it as an excellent choice for discomfort-prone patients — spheri- cal, astigmatic, and presbyopic — who would beneft from a lens that helps keep moisture in and irritation out. OM Spotlight on Science