DOCSLIB.ORG

University of Bradford Ethesis

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
University of Bradford Ethesis University of Bradford eThesis This thesis is hosted in Bradford Scholars – The University of Bradford Open Access repository. Visit the repository for full metadata or to contact the repository team © University of Bradford. This work is licenced for reuse under a Creative Commons Licence. Ocular Biometric Change in Orthokeratology An investigation into the effects of orthokeratology on ocular biometry and refractive error in an adult population Annette PARKINSON Submitted for the degree of Doctor of Philosophy Bradford School of Optometry and Vision Science 2012 Annette Parkinson Title: Ocular Biometric Change in Orthokeratology Keywords: Orthokeratology, Ocular Biometry, Corneal Topography, Refractive error ABSTRACT Aim; This study looks at the effect of orthokeratology on a number of biometric parameters and refractive error in an adult population. Method; Forty three myopic subjects were recruited to a twelve month study into the effects of orthokeratology on ocular biometry and refractive error. Two different back surface lens designs were applied right eye) pentacurve and left eye) aspheric. The aspheric design was chosen to more closely mimic the cornea’s natural shape. Anterior and posterior apical radii and p-values; corneal thickness and anterior chamber depth were measured using the Orbscan IIz; together with ocular biometry by IOL Master and a standard clinical refraction. All measurements were repeated at one night, one week, one, three, six and twelve months. Refractive changes were analysed against biometric changes. Results; Twenty seven participants completed one month of lens wear. Twelve subjects completed twelve months of lens wear. Subjects with myopia ≤ -4.00DS were successfully treated with orthokeratology. Both anterior and posterior apical radii and p values were altered by orthokeratology. Corneal thickness changes were in agreement with previously published studies. Axial length and anterior chamber depth were unaffected by the treatment. Conclusion; Orthokeratology should be available as an alternative to laser refractive surgery. It is best restricted to myopes of up to -4.00DS with low levels of with the rule corneal astigmatism. The use of an aspheric back design contact lens did not produce a significant benefit over that of a pentacurve. i Acknowledgements I am indebted to my three supervisors for their support throughout the period of this study; Professor W.A.Douthwaite for his initial guidance and inspiration at the outset, Dr E.A.H. Mallen for his constant support, advice and guidance throughout the study, and Dr J.M. Gilchrist for stepping in to assist in the latter stages following Professor Douthwaite’s retirement. I am grateful to No 7 Contact Lenses for providing all the lenses used in the study. I would like to acknowledge those participants who took part in this longitudinal study, particularly for their willingness to attend the early morning measurement sessions. I would like to thank all my colleagues at the Bradford School of Optometry and Vision Science, particularly Ms Catherine Viner, for their enthusiastic encouragement. Lastly I would like to thank my family for their support. ii CONTENTS Chapter 1 Introduction 1 1.1 Historical Perspective 1.1.1 The Berkeley Orthokeratology Study 1.1.2 The Tabb Method 1.2 Reverse Geometry lenses (circa 1989) 19 1.3 Overnight wear of lenses 23 1.4 Corneal Changes associated with Orthokeratology 24 1.5 Predicting success with Orthokeratology 28 1.6 Mathematical Model of the cornea 30 1.7 Axial edge lift in contact lens design 39 1.8 Retention and Regression 41 1.9 Corneal Biomechanics and Mechanisms of Orthokeratology 43 1.10 Comparative Lens design studies in orthokeratology 46 1.11 Control of Myopia with Orthokeratology 49 1.12 Complications associated with Orthokeratology 51 1.12.1 Corneal staining 1.12.2 Microbial Keratitis 1.12.3 Iron ring deposition in orthokeratology 1.12.4 Other corneal events 1.13 Non Orthokeratology uses of reverse geometry lenses 66 1.13.1 Trauma 1.13.2 Post operative complications of Refractive surgery 1.13.3 Post operative management of corneal grafts iii 1.14 Summary 67 1.15 Study rationale and aims 71 Chapter 2 Preliminary Studies 74 2.1 Measurement error and repeatability 76 2.2 The Orbscan II 80 2.2.1 Introduction 2.2.2 Image production 2.2.3 Pachymetry 2.3 Previous Orbscan repeatability studies 90 2.4 Orbscan Repeatability 94 2.4.1 Anterior repeatability on corneas 2.4.1.1 Method 2.4.2 Posterior repeatability on corneas 2.4.2.1 Method 2.4.3 Posterior repeatability using test surfaces 2.4.3.1 Method 2.5 Orbscan Repeatability Results 100 2.5.1 Anterior 2.5.1.1 Global 2.5.1.2 Single meridian 2.5.2 Posterior cornea 2.5.2.1 Global 2.5.2.2 Single meridian 2.5.3 Posterior surfaces 2.6 Orbscan Discussion 122 2.6.1 Anterior cornea 2.6.2 Posterior cornea iv 2.6.3 Posterior surfaces 2.7 Study limitations 126 2.8 The EyeSys Corneal Analysis System (2000) 127 2.8.1 Introduction 2.9 Method 131 2.9.1 Image capture 2.9.2 Analysis 2.10 Results Comparison of Orbscan and EyeSys apical radius and p value 134 2.11 Discussion 140 2.12 The IOL Master 141 2.12.1 Introduction 2.13 IOL Master Method 144 2.13.1 Axial length measurements 2.13.2 Anterior chamber depth measurements method 2.14 Collar and Pillar 147 2.14.1 Introduction 2.15 Calculation of Pillar diameters 148 2.15.1 Method 2.15.2 BOZR measurements 2.15.3 Sag measurements 2.15.4 Measurement of lens sag for an unknown lens 2.15.5 Example of calculation of sag for comparison with the three pillar diameters used for verification purposes 2.15.6 Verification of orthokeratology lenses 2.16 Results 154 2.16.1 Pentacurve design 2.16.2 Aspheric design v 2.17 Discussion 163 Chapter 3 Protocols and Initial Outcomes 164 3.1 Introduction 164 3.2 Subject recruitment for orthokeratology study 165 3.3 Initial assessment 166 3.4 Power vectors (Thibos, Wheeler & Horner 1997) 169 3.5 Lens design appointment 171 3.6 Lens design protocols 173 3.6.1 C5 design 3.6.2 Aspheric design 3.7 Collection protocol 181 3.8 Protocol for first overnight visit 185 3.9 Study profiles 186 3.10 Statistical analysis 191 3.11 Power analysis (A priori) 191 Chapter 4 Anterior Corneal Response 193 4.1 Introduction 193 4.1.1 Anterior apical radius 4.1.2 Asphericity 4.1.3 Effect of orthokeratology on refractive error 4.1.4 Effect of orthokeratology on astigmatism 4.2 Anterior corneal response methods 203 4.2.1 Apical radius and p value change 4.2.2 Corneal sag change 4.2.3 Agreement between pentacurve BOZR and anterior apical radius of the right eye 4.2.4 Agreement between the aspheric lens sag and corneal sag of the left eye vi 4.2.5 Refractive error 4.2.6 Corneal power change 4.2.7 Anterior vertical cornea 4.2.8 VAR rating 4.2.9 Treatment zone diameter and decentration 4.2.10 Physiological response 4.3 Results 211 4.3.1 Anterior apical radius and p value 4.3.2 Corneal sag 4.3.3 Results for the pentacurve BOZR and right eye apical radius and the aspheric lens sag and left corneal sag 4.3.4 Results for corneal sag 4.3.5 Results for refractive error 4.3.6 Results for corneal power 4.3.7 Results for vertical cornea 4.3.8 Results for VAR 4.3.9 Results for the treatment zone 4.3.10 Results for the physiological response 4.4 Discussion 252 4.4.1 Apical radius and p value change 4.4.2 BOZR and apical radius and lens sag and corneal sag 4.4.3 The relationship between corneal power and refractive error in orthokeratology 4.4.4 Vertical cornea 4.4.5 Visual acuity and orthokeratology (VAR) results 4.4.6 Treatment zone and decentration 4.4.7 Physiological response 4.5 Conclusion 263 vii Chapter 5 Topography Posterior 264 5.1 Introduction 264 5.1.1 The effect of orthokeratology on the posterior cornea 5.2 Posterior surface 269 5.2.1 Method 5.2.2 Results 5.3 Discussion 273 Chapter 6 Corneal thickness response 274 6.1 Introduction 274 6.1.1 Introduction effect of orthokeratology on corneal thickness 6.1.2 Central corneal thickness measures by Orbscan 6.2 Repeatability of the initial corneal thickness measures 278 6.2.1 Method and data analysis 6.3 Change in corneal thickness at each visit for the twelve months of the study 279 6.3.1 Method and data analysis 6.4 Results 280 6.4.1 Repeatability of the initial corneal thickness measures 6.4.2 Results change in corneal thickness at each visit for the twelve months of the study 6.4 Discussion 289 viii Chapter 7 Anterior Chamber and Axial length effects of orthokeratology 294 7.1 Introduction 294 7.1.1Anterior chamber depth 7.1.2 Axial length 7.1.3 Axial length changes in orthokeratology 7.2 Anterior chamber and axial length measurements 302 7.2.1 Anterior chamber method 7.2.2 Axial length method 7.3 Results 303 7.4 Discussion 311 Chapter 8 Optical Modelling 312 8.1 Ocular aberrations and orthokeratology 8.1.1 Root mean square (RMS) 8.1.2 Zernike polynomials 8.1.3 Ocular component contributions to aberrations 8.2 Effect of orthokeratology on higher order ocular aberrations 8.3 The effect of orthokeratology on higher order ocular aberrations in the study group 323 8.3.1 Method 8.3.2 Results 8.4 Discussion 329 8.4.1 Interaction between biometric factors Chapter 9 Conclusions 333 9.1 Clinical considerations 9.2 Power analysis (Post Hoc) 9.3 Limitations of the current study 9.4 Future work References 345 ix Appendices 372 A.
Load more

Recommended publications
  • View to Define Contact Lens Discomfort And
    Contact Lens Discomfort, Vision Correction Preferences, and Accommodative Treatment in Presbyopic and Non-Presbyopic Contact Lens Wearers Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Erin Marie Rueff, OD, MS Graduate Program in Vision Science The Ohio State University 2018 Dissertation Committee Melissa Bailey, OD, PhD, Advisor Donald Mutti, OD, PhD Teng Leng Ooi, PhD Loretta Szczotka-Flynn, OD, PhD ii Copyrighted by Erin Marie Rueff 2018 iii Abstract Discomfort is the most cited reason for dissatisfaction with and discontinuation of contact lens wear. Most discomfort is attributed to dry eye-type etiologies, but uncomfortable contact lens wearers commonly show few objective signs of dryness, and treatments aimed at eliminating dryness often fail. Uncomfortable contact lens wearers, however, also report symptoms that are similar to binocular vision and accommodative disorders. Research in our laboratory suggested that uncomfortable wearers have an increased incidence of accommodative insufficiency and led us to hypothesize that contact lens discomfort is influenced by symptoms associated with visual discomfort and accommodative fatigue. The projects described in this dissertation sought to better understand how accommodative decline in presbyopes affects comfort and contact lens discontinuation and how alleviation of accommodative demand in non-presbyopes via a multifocal contact lens affects discomfort and satisfaction with contact lens wear. Presbyopes, a group with known accommodative insufficiency, are also known for being particularly uncomfortable contact lens wearers. Few studies, however, have specifically addressed presbyopic reasons for contact lens discontinuation. The first experiment in this dissertation describes a survey study that aimed to determine why presbyopes discontinued contact lens wear and how factors like vision and comfort influenced dropout.
    [Show full text]
  • Professional Fitting And
    PROFESSIONAL FITTING AND INFORMATION GUIDE PARAGON RG-4™ Manufactured in Paragon HDS® 100 (paflufocon D) RIGID GAS PERMEABLE CONTACT LENSES FOR CORNEAL RESHAPING OVERNIGHT WEAR 1 TABLE OF CONTENTS Page Introduction 3 Product Description 3 Actions 6 Indications (Uses) 6 Contraindications 6 Warnings 6 Adverse Effects (Problems and What to Do) 6 Precautions 6 Selection of Patients 6 Fitting Concept 7 Predicting Lens Results 7 Clinical Study Data 7 Risk Analysis 7 Fitting Paragon RG-4™ Contact Lenses for Corneal Reshaping 8 Pre-fitting Examination 8 Initial Lens Power Selection 8 Initial Lens Diameter Selection 8 Initial Lens Base Curve Selection 8 Initial Lens Evaluation 8 Characteristics of a Tight Lens 9 Characteristics of a Loose Lens 9 Diagnostic Lenses 9 Corneal Reshaping Problem Solving 10 Follow-Up Care 12 Recommended Initial Wearing Schedule 12 Myopic Reduction Maintenance Lens (Retainer Lens) Wearing Schedule 13 Handling Of Lenses 13 Patient Lens Care Directions 13 Vertex Distance and Keratometry Conversion Charts 13 How Supplied 13 Reporting Of Adverse Reactions 14 2 INTRODUCTION Paragon RG-4™ Contact Lenses for Corneal Reshaping produce a temporary reduction of myopia by reversibly altering the curvature of the cornea. The Paragon RG-4™ contact lenses are manufactured from Paragon HDS® 100. A slight reduction of the curvature of the cornea can reduce the excessive focusing power of the myopic eye. If the amount of corneal reshaping is precisely controlled as is the objective of Paragon RG-4™ lens design, it is possible to bring the eye into correct focus and completely compensate for myopia. After the contact lens is removed, the cornea retains its altered shape for all or most of one’s waking hours.
    [Show full text]
  • Optical Theory Simplified: 9 Fundamentals to Becoming an Optical Genius APPLICATION NOTES
    LEARNING – UNDERSTANDING – INTRODUCING – APPLYING Optical Theory Simplified: 9 Fundamentals To Becoming An Optical Genius APPLICATION NOTES Optics Application Examples Introduction To Prisms Understanding Optical Specifications Optical Cage System Design Examples All About Aspheric Lenses Optical Glass Optical Filters An Introduction to Optical Coatings Why Use An Achromatic Lens www.edmundoptics.com OPTICS APPLICATION EXAMPLES APPLICATION 1: DETECTOR SYSTEMS Every optical system requires some sort of preliminary design. system will help establish an initial plan. The following ques- Getting started with the design is often the most intimidating tions will illustrate the process of designing a simple detector step, but identifying several important specifications of the or emitter system. GOAL: WHERE WILL THE LIGHT GO? Although simple lenses are often used in imaging applications, such as a plano-convex (PCX) lens or double-convex (DCX) in many cases their goal is to project light from one point to lens, can be used. another within a system. Nearly all emitters, detectors, lasers, and fiber optics require a lens for this type of light manipula- Figure 1 shows a PCX lens, along with several important speci- tion. Before determining which type of system to design, an fications: Diameter of the lens (D1) and Focal Length (f). Figure important question to answer is “Where will the light go?” If 1 also illustrates how the diameter of the detector limits the the goal of the design is to get all incident light to fill a detector, Field of View (FOV) of the system, as shown by the approxi- with as few aberrations as possible, then a simple singlet lens, mation for Full Field of View (FFOV): (1.1) D Figure 1: 1 D θ PCX Lens as FOV Limit FF0V = 2 β in Detector Application ƒ Detector (D ) 2 or, by the exact equation: (1.2) / Field of View (β) -1 D FF0V = 2 tan ( 2 ) f 2ƒ For detectors used in scanning systems, the important mea- sure is the Instantaneous Field of View (IFOV), which is the angle subtended by the detector at any instant during scan- ning.
    [Show full text]
  • Techspec® Precision Aspheric Lenses Precision Techspec® by Edmund Optics by Edmund High Numerical Apertur High Numerical Gener Designed and Manufactur Designed
    Edmund Optics® BROCHURE ASPHERIC LENSES ® COPYRIGHT 2017 EDMUND OPTICS, INC. ALL RIGHTS RESERVED 1/2017 RIGHTS RESERVED ALL 2017 EDMUND OPTICS, INC. ® COPYRIGHT PRODUCTS & CAPABILITIES Contact us for a Stock or Custom Quote Today! UK: +44 (0)1904 788600 | GERMANY: +49 (0)721 6273730 [email protected] | FRANCE: +33 (0)8 20 20 75 55 www.edmundoptics.eu/aspheres-17 CNC POLISHING CAPABILITIES Edmund Optics® is a premier manufacturer of aspheric lenses, producing thousands of precision polished aspheres each month. Lenses are manufactured from a variety of Schott, Ohara, and CDGM glasses, fused silica, and a multitude of fluoride and crys- talline materials. Edmund Optics® utilizes state-of-the-art CNC equipment for coarse and fine grinding and polishing of aspheric lenses with convex or concave geometries. Deterministic figure correction through Magneto-Rheological polishing is available for the ulti- mate in precision (see MRF Polishing Capabilities). Aspheric Manufacturing Capabilities Commercial Precision High Precision Diameter 10 - 150 mm 10 - 150 mm 10 - 150 mm Diameter Tolerance +0/-0,100 mm +0/-0,025 mm +0/-0,010 mm Asphere Figure Error (P - V) 5 μm 0,632 - 1,5 µm < 0,312 µm Vertex Radius (Asphere) ±1% ±0,1% ±0,05% Radius (Spherical) ±0,3% ±0,1% ±0,025% ® COPYRIGHT 2017 EDMUND OPTICS, INC. ALL RIGHTS RESERVED 1/2017 RIGHTS RESERVED ALL 2017 EDMUND OPTICS, INC. ® COPYRIGHT Power (Spherical) 2λ λ/2 λ/10 Irregularity (Spherical) λ/2 λ/4 λ/20 Sag2 25 mm max. 25 mm max. 25 mm max. Typical Slope Tolerance1 1 μm/mm 0,35 μm/mm 0,15 μm/mm Centering (Beam Deviation) 3 arcmin 1 arcmin 0,5 arcmin Center Thickness Tolerance ±0,100 mm ±0,050 mm ±0,010 mm Surface Quality (Scratch Dig) 80-50 40-20 10-5 Aspheric Surface Metrology Profilometry Profilometry Interferometry Slope specification: Diameter PV (Height) Sag (μm) θ Center Thickness Slope Window (1mm) Figure 1: Slope error quantifies the rate of change Figure 2: General geometry of an aspheric lens.
    [Show full text]
  • LDII16 Lens Design II
    Lens Design II Lecture 8: Special correction features I 2016-12-07 Herbert Gross Winter term 2016 www.iap.uni-jena.de 2 Preliminary Schedule 1 19.10. Aberrations and optimization Repetition Zero operands, lens splitting, lens addition, lens removal, 2 26.10. Structural modifications material selection Correction with aspheres, Forbes approach, optimal location 3 02.11. Aspheres of aspheres, several aspheres 4 09.11. Freeforms Freeform surfaces Astigmatism and field curvature, thick meniscus, plus-minus 5 16.11. Field flattening pairs, field lenses Achromatization, axial versus transversal, glass selection 6 23.11. Chromatical correction I rules, burried surfaces secondary spectrum, apochromatic correction, 7 30.11. Chromatical correction II spherochromatism 8 07.12. Special correction topics I Symmetry, wide field systems,stop position 9 14.12. Special correction topics II Anamorphotic lenses, telecentricity 10 21.12. Higher order aberrations high NA systems, broken achromates, induced aberrations 11 04.01. Further topics Sensitivity, scan systems, eyepieces 12 11.01. Mirror systems special aspects, double passes, catadioptric systems 13 18.01. Zoom systems mechanical compensation, optical compensation color correction, ray equivalent model, straylight, third order 14 25.01. Diffractive elements aberrations, manufacturing 15 01.02. Realization aspects Tolerancing, adjustment 3 Contents 1. Symmetry 2. Camera lenses 3. Stop position 4. Vignetting 4 Principle of Symmetry . Perfect symmetrical system: magnification m = -1 . Stop in centre of symmetry . Symmetrical contributions of wave aberrations are doubled (spherical) . Asymmetrical contributions of wave aberration vanishes W(-x) = -W(x) . Easy correction of: coma, distortion, chromatical change of magnification front part rear part 2 3 1 5 Symmetrical Systems Ideal symmetrical systems: .
    [Show full text]
  • 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.
    [Show full text]
  • Complete Course in Dispensing
    Continuing education CET Complete course in dispensing Part 6 – Lens selection After last month’s article (November 14, 2008) discussing the basic properties of materials used for the manufacture of spectacle lenses, Andrew Keirl and Richard Payne give an overview of the vast selection of lens types and designs available for the ‘normal’ power range. Module C10361, two general CET points ith the prevalence of wavelengths. These are the chromatic online information aberrations (6) which were addressed available for consum- in article 5 of this series. The six aberra- ers today, many lens tions are: manufacturers have 1 Spherical aberration -4.00 -2.00 -4.00 -8.00 -6.00 -4.00 Wseen the need to enhance their product +8.00 +6.00 +4.00 +4.00 +2.00 +0.00 2 Coma ranges with marketable brands, employ- 3 Oblique astigmatism ing household names and retail market- 4 Curvature of field ing tactics to ensure their lens ranges are 5 Distortion more appealing. With such an extensive +4.00 D lenses -4.00 D lenses 6 Chromatic aberration (TCA) range of options now available, it is A best form spectacle lens is a lens vital that practitioners can see past the Figure 1 designed to minimise the effects of ever increasing lists of brand names and Lens form oblique astigmatism and therefore marketing terminology used to properly comparisons provide the best possible vision in consider the true attributes of any given oblique gaze. Secondary considerations lens design and use the appropriate are distortion and transverse chromatic ‘tool’ for the appropriate ‘job’.
    [Show full text]
  • Spherical Aberration Compensation Plates
    Optical Components Spherical aberration compensation plates Scott Sparrold, Edmund Optics, Pennsburg, Pennsylvania, USA Anna Lansing, Edmund Optics GmbH, Karlsruhe, Germany Imaging optics strive to obtain perfect or near diffraction limited performance. The main detriment to imaging systems is spherical aberration, and it costs money and effort to eliminate or minimize. This article will outline a new optical component for controlling this aberration. Typical optical components are standard- ly, the article will explore compari- ized to focal length and diameters but sons between aspheres, spherical not so much to their level of aberration. lenses and spherical aberration Within the last decade aspheric lenses have plates in typical user applications. become a commodity, basically eliminating spherical aberration for a single wave- 1 Theory of spherical aberration lens produces “undercorrected” spherical length and specifi c imaging parameters. aberration, defi ned as the marginal rays The introduction of spherical aberration To obtain a mathematically perfect image, focusing closer to the lens than the paraxial plates provides another tool for construct- a mirror requires a parabolic surface while a rays. For a collimated beam and a spherical ing systems that can adequately control lens requires an elliptical surface (Lüneburg lens, equation 1 describes the deviation W and manipulate light. lens) [1]. For ease of manufacturing and from an ideal spherical wavefront [2]. This article will highlight typical scenarios testing, however, most optical elements W = W · ρ4 (Eq.1) involving spherical aberration and demon- have spherical surfaces. This introduces 040 strate how to control it. We’ll discuss the blur or a halo in the image due to spheri- where W040 is the wavefront aberration magnitude of the aberration via equations cal aberration, which results from differ- coeffi cient for spherical aberration (units and general rules of thumb.
    [Show full text]
  • Presbyopia Correction of a Higher Order Introducing the TECNIS® Multifocal IOL
    Presbyopia Correction of a Higher Order Introducing the TECNIS® Multifocal IOL. The first and only pupil independent, full diffractive, wavefront-designed aspheric lens that corrects spherical aberration to essentially zero and reduces chromatic aberration. High-quality vision in any light condition • Near, far, and intermediate: Excellent vision day or night1 • Proprietary non-apodized optic and proven clear hydrophobic acrylic for best image quality Exceptionally high patient satisfaction • Over 94% of patients:2 – Achieve simultaneous 20/25 or better distance and 20/32 or better near – Function comfortably without glasses for ALL distances, including intermediate – Would choose the TECNIS® Multifocal IOL again • Nearly 9 out of 10 patients NEVER wear glasses2 • Low-light reading speed is twice as fast compared to ReSTOR® IOL3 • Delivers a predictable and consistent full range of vision with less halos than other PC-IOLs2,4,5 REFG-5466 TMF Sales sheet V15.indd 1 10/27/08 1:56:43 PM Highest Patient Satisfaction With Proven Superior Results Clinical Data Comparison Data from the US clinical trial demonstrate that the TECNIS® Multifocal IOL provides better performance and extremely high patient satisfaction compared to the ReSTOR® Aspheric IOL.2,4 The study shows that the TECNIS® Multifocal IOL consistently delivers high-quality vision with reports of less halos and glare than other presbyopia-correcting IOLs for optimal visual results.2,4,5 TECNIS® ReSTOR® Aspheric Crystalens® Multifocal IOL2 One-piece IOL4 IOL5 Patient satisfaction 94.6%
    [Show full text]
  • Contact Lens Alternatives for Presbyopia
    8/16/2019 Multifocal Contact Lens Patient Selection, Fitting and Presbyopic Market Problem-Solving • 74 million Baby Boomers born between 1946‐1964* • 66 million Generation Xers born between 1965‐1980* • In 2010, about 1/3 of US population was between 40‐ Edward S. Bennett, OD, MSEd, FAAO and 59 years of age. Vinita Allee Henry, OD, FAAO • In 2015 US census data reports 40% of the population is over 45 • In the next decade, 28% of all contact lens wearers will COPE Course ID: 63329‐CL be >50 y.o. Qualified Credit: 2 hour(s) • 90% of all CL wearers between 35‐55 have worn CL’s majority of their life *Pew Research Center Presbyopic Market Growth of Multifocals from Contact Lens Spectrum 1/2019 • Steady growth of multifocals • Surpassed monovision • Presbyopes are in their peak earning period • Knowledge of multifocal contact lenses is limited • More tech savvy, desire high technology • Want information • Fit early Contact Lens Spectrum 1/2016 Contact Lens Alternatives for Presbyopia • Single Vision/Reading Spectacles • Monovision • Bifocals/ Multifocals 1 8/16/2019 Monovision Issues Driving/Critical Vision Tasks • Depth Perception • Monovision wearers have difficulty suppressing • Possible Suppression headlights with night driving with one-third experiencing glare • Contrast Sensitivity/Vision Loss • It is advised for monovision patients to avoid • Night Driving driving or operating dangerous machinery • Liability during adaptation • Over-correction spectacles strongly recommended MONOVISION VERSUS CL BI/MULTIFOCALS • Johnson J, et al; Multivision Vs. Monovision: A comparative study: presented at CLAO, Feb, 2000 • 6 weeks GP multifocal; 6 weeks monovision (or vice versa) • 75% who completed study preferred multifocal Monovision Versus CL CL MULTIFOCALS DO NOT WORK .
    [Show full text]
  • A Comparison and Evaluation of Aspheric Lens Designs Terry Draeger Kyle Fairless Tom Norfleet
    A COMPARISON AND EVALUATION OF ASPHERIC LENS DESIGNS 1994 TERRY DRAEGER KYLE FAIRLESS TOM NORFLEET ABSTRACT: Six aspheric, single vision lens designs, were subjectively and objectively compared by four non-presbyopic, hyperopic patients. The lenses chosen were Sola Optical's ASL Polycarbonate and Spectralite, Rodenstock's Cosmolit, American Optical's Aspherlite, Silor Optical's Hyperal, and Gentex Optic's Profile. The subjects were previously wearing spherical design single vision spectacles or contact lenses to correct their ametropia. Two of the four subjects preferred the Spectralite Aspherics overall, while the remaining two subjects preferred their habitual contact lenses. INTRODUCTION: Hyperopic patients have long been subject to heavy, thick­ centered, and magnified appearing prescription eyeglasses. Lens manufacturers are continually striving to design new materials free from distortions and other aberrations which become detrimental to image quality and a patients ability to function on both a visual and cosmetic basis. Studies have been conducted which have attempted to describe the aberrations produced by spherical as well as aspherical lenses (1) . Similarly, studies describing measuring and/or comparing distortions produced by progressive addition lenses have been described (2,3,4). Single vision, aspheric lenses are an example of how lens designers have tried to meet the visual and cosmetic needs of the non-presbyopic, hyperopic patient, by utilizing the Cartesian Oval Theory with different lens materials (5). This study was conducted to assess the consequences of fitting non-presbyopic, hyperopic, spherical design spectacle or contact lens wearers with six different aspheric lens designs in order to determine which design(s) seems best based upon subjective and objective subject responses.
    [Show full text]
  • Aspheric Lens Design
    ASPHERIC LENS DESIGN This is a very basic and simple approach to explaining aspheric lenses. They feature a different lens design than the standard spherical lens. To understand the aspheric concept, you have to consider two components of a lens that affect how light travels through the lens. The first is the index of refraction and secondly is the lens curve. The index of refraction is a function of the material and the lens curve is a function of lens design. By manipulating the curves on the front and back surface of a lens, a prescription power is created. For some prescription powers, spherical lenses require the selection of steep base curves to compensate for the angle at which the eye looks through the lens as it moves from the center to the periphery. The result is thick edges for minus lenses and thick, bulbous centers for plus lenses. When a flatter base curve is selected over the traditional curves, some aberrations increase, particularly oblique astigmatism and off-axis power errors. These distortions are inherent in the design nature of spherical curves. By contrast, aspherical base curves change shape and power across the surface of a lens. That change in power is gradual. This change in power and curve follows the natural movement of the eye as it looks from the center of the lens out to the periphery. Because of this change in power and curve, the lens is flatter and thinner, but the peripheral distortions are minimized, thus off-power axis error are not created. Aspheric designs require computer programs to calculate the numerous power or curve changes.
    [Show full text]