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Correction Of Correction of Presbyopia with GP Contact Lenses Development of the Correction of Presbyopia with GP Contact Lenses booklet was supported through an educational grant from Acknowledgements Polymer Technology, a Bausch & Lomb company. REVIEWERS Albert Noguera Kathryn Dumbleton, MSc, FAAO Director General, Conóptica S.L. Senior Clinical Scientist, Centre for Contact Lens Research Barcelona, Spain EXECUTIVE EDITOR Waterloo, Canada Desmond Fonn, MOptom, FAAO Craig W. Norman, FCLSA Director, Centre for Contact Lens Research Ron Beerten, OD, FAAO South Bend Clinic Professor, School of Optometry, University of Waterloo Director Professional Services, Procornea South Bend, Indiana, USA Eerbeek, Netherlands PROJECT MANAGER Kirstin P. Rhinehart, OD Bonnie Boshart, BBA Hans Bleshøy, BSc, Ph.D, MCOptom, FAAO South Bend Clinic Business Development Coordinator, Centre for Contact Lens Research Danish Contact Lens Consultants South Bend, Indiana, USA Skive, Denmark AUTHORS Philippe Seira, Dipl. Augenoptiker Luigina Sorbara, OD, MSc, FAAO Alex Cannella, RN, FCLSA Lecturer at the University of Applied Sciences, Clinical Scientist, Centre for Contact Lens Research Contact Lens Educator / Consultant Northwestern Switzerland Associate Professor, School of Optometry, University of Waterloo Westford, Massachusetts, USA Olten, Switzerland Craig Woods, PhD, FAAO William Edmondson, MAT, OD, FAAO Frank Widmer, Dipl. Ing. (FH) Augenoptik Research Manager, Centre for Contact Lens Research Professor of Optometry & Chief, Contact Lens Service Hecht Contactlinsen GmbH Adjunct Associate Professor, School of Optometry, University of Waterloo Northeastern State University, College of Optometry Freiburg, Germany Tahlequah, Oklahoma, USA EDITOR Michael Wyss, Dipl. Augenopiker, FAAO Alisa Sivak, MA Michael A. Johnson, FCLSA Kontactlinsen Studio H+M Bärtschi Communications Coordinator, Centre for Contact Lens Research Director of Consultation Services, Art Optical, Inc. Bern, Switzerland Grand Rapids, Michigan, USA CONTRIBUTORS DESIGN Jill Woods, MCOptom Ulrich Maxam, Dipl.Ing. (FH) Staatl. geprüfter Augenoptiker Graphics, University of Waterloo Clinical Scientist, Centre for Contact Lens Research Rostock, Germany Christina Englund Steven Byrnes, OD Prof. Dr. Peter Moest, Augenoptik/Optometrie im FB VII TFH Senior Graphic Designer Optometrist, New Hampshire, USA Berlin, Germany Boston Products Group, Bausch & Lomb Inc. Eef van der Worp, BOptom, FAAO, FIACLE Bruce W. Morgan, OD, FAAO Sophie Celia Xu Optometrist, Netherlands Professor, Michigan College of Optometry at Ferris State Photographer University Brian Tompkins, BSc (hons) FCOptom Big Rapids, Michigan, USA Optometrist, United Kingdom 2 Correction of Presbyopia with GP Contact Lenses Opportunity knocks 3 contents Table of Contents 2 Acknowledgements 48 Fitting non-rotational lens designs 6 Introduction 52 Case Study: non-rotational lenses 56 Evaluating the fit of non-rotational lens designs 10 CHAPTER 1: Opportunity knocks 65 Optimizing the fit of non-rotational designs 10 Who are today’s presbyopes? Meeting your patient’s needs. 66 Other options 12 Today’s GP lenses for presbyopia: getting better all the time 66 Center: near designs 14 The presbyopic eye 69 Modified monovision 15 Take-home points 71 Take-home points 16 CHAPTER 2: Principles, designs and lens fitting: ensuring patient success 72 CHAPTER 3: Next steps 17 How to approach the fitting of GP multifocals 73 Getting started: make decisions 17 Design principles 76 Prepare 18 Rotational designs 78 Market your skills 20 Non-rotational designs 78 Market GP multifocals in your practice 22 Simultaneous designs 79 Communicating with your patients 23 Fitting GP multifocals: an overview 80 Take-home points 26 Matching designs with patients 28 Rotational lens designs 81 CHAPTER 4: Frequently asked questions 29 Non-rotational lens designs 81 Questions from practitioners 31 Fitting rotational lens designs 84 Questions from patients 34 Case Study 1: spherical rotational lenses 85 Appendix A: Sample form: Contact lens workup 36 Case Study 2: aspheric rotational lenses 86 Appendix B: Keratometer readings conversion chart 38 Evaluating the fit of rotational lens designs 47 Optimizing the fit of rotational lens designs 87 Appendix C: Conversion chart: Near vision nomenclature 4 Correction of Presbyopia with GP Contact Lenses Opportunity knocks 5 How to read this book TERMINOLOGY You may have recognized inconsistencies in the terminology used to describe the fitting of GP multifocal contact lenses. For example, ‘translating’, ‘alternating’ and ‘segmented’ contact lenses can all refer to the same lens design. The following is a list of terminology you will find throughout this booklet. Introduction GP MULTIFOCAL LENS DESIGNS: Alternating lens: An outdated term referring to a lens with distinct optical portions that rely on lens movement to position the distance and near optic zones in front of the pupil. In this booklet we refer to these as ‘non-rotational’ lenses. Bifocal lens: Bifocal contact lenses correct presbyopia by incorporating two distinct power segments, one correcting the distance prescription and one correcting the near prescription. These contact lenses correct presbyopia by mimicking bifocal spectacles, with a distance segment at the top and a near segment below. In this booklet we refer to these as ‘non-rotational’ lenses. Binocular over-refraction: This method of over: refracting has one eye fogged (blurred), using a About this book The Centre for Contact +0.75D spherical lens, while optimizing the acuity of the contralateral eye with either the addition of plus or minus lenses. Presbyopia can be safely and effectively Lens Research Elliptical shapes: The shape of the cornea varies from a sphere (shape factor of 0) as it has a curvature corrected with gas permeable (GP) multifocal Established in 1988, the Centre for Contact that flattens as you approach the periphery (relative to the center of the cornea). This is referred to as a (bifocal) contact lenses, but statistics indicate Lens Research at the School of Optometry, prolate shape and resembles an ellipse (an egg standing on its end) with a shape factor between 0 and 1.0. that they remain the most underutilized University of Waterloo in Canada focuses its contact lenses on the market. We believe research on the effects of contact lens wear Fused segments: These are segments of higher refractive index material inserted into the body of the contact lens, to generate the near reading segment. This type of design is not currently available in GP that practitioners have been ‘turned off’ GP on the eye. Made up of faculty, researchers materials. multifocals due to their experiences with older and administrative and technical staff, generations of these lenses, which tended to be clinical trials and basic research performed at Hyperbolic shapes: When the cornea resembles a highly positive prolate shape, as in keratoconus difficult to fit, with poor visual results. the CCLR is for the most part the result of (i.e. the cornea is very steep centrally and relatively very flat in the periphery) then the corneal shape factor may more closely resemble a hyperbola (shape factor ›1.0). collaboration with a variety of contact lens and Fortunately, GP multifocals have come a related companies. Many of our activities are Multifocal lens: Correct presbyopia by incorporating an additional optical zone (or zones) correcting long way, and practitioners who avoid fitting also directed at supporting the development intermediate, distance and near vision. them are missing out on an important niche of optometric education for practitioners. market. With this booklet, we hope to show Please visit http://cclr.uwaterloo.ca for more you just how far GP multifocals have come and information about our work. demonstrate the ease with which they can now be fit and managed. 6 Correction of Presbyopia with GP Contact Lenses Opportunity knocks 7 Non-rotational lens design: Distance (D) and near (N) portions (usually segments) are directionally ABBREVIATIONS: sensitive. The distance portion and near portions usually mimic the positions found within a pair of spectacles. BOZD: Back optic zone diameter BOZR: Back optic zone radius (formerly known as base curve) BVP: Back vertex power HVID: Horizontal visible iris diameter TBUT: Tear break: up time TD: Total diameter (of the contact lens) Rotational lens design: Concentric optical zones (or gradient optical powers) are co-axial with the geometric center of the contact lens. PA: Palpebral aperture PS: Pupil size ∆: Prism diopters ASSUMPTIONS We wrote this guide with a number of assumptions in mind: 1. Gas permeable multifocals are a good alternative to soft hydrogel multifocals. Segment: The optical zone of the contact lens may have clearly defined (near and distance) optical portions, 2. Fitting GP multifocals is not as difficult as practitioners may think. called ‘segments.’ 3. Every presbyopic patient should be given the opportunity to try multifocal contact lenses. Simultaneous vision lens design: Positions both the distance and near portion of the optical zone in front 4. Taking a proactive approach is the best way to ensure that all presbyopic patients of the pupil at the same time. see multifocal contact lenses as an option. Varifocal lens: Multifocal lens incorporating optical zone powers that transition gradually from distance These assumptions are fundamental to this booklet: We believe that GP multifocals are superior in many to near correction. ways to their soft contact
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