Additional Information
Book Details
Abstract
Thoroughly revised and updated, this popular book provides a comprehensive yet easy to read guide to modern contact lens practice. Beautifully re-designed in a clean, contemporary layout, this second edition presents relevant and up-to-date information in a systematic manner, with a logical flow of subject matter from front to back.
This book wonderfully captures the ‘middle ground’ in the contact lens field … somewhere between a dense research-based tome and a basic fitting guide. As such, it is ideally suited for both students and general eye care practitioners who require a practical, accessible and uncluttered account of the contact lens field.
- Outlines a rational clinical approach to modern contact lens fitting - practical advice for the clinic and the classroom
- Logical structure and systematic layout, with relevant chapters grouped into coherent sections for easy reference
- Up-to-date for accurate information
- Chapters are contextualised through cross-referencing - helping to reflect the relative importance of different topics
- Provides an 'historical time line' of contact lens development and explains the current global situation
- Explains how contact lenses are fabricated, designed, manufactured and measured
- Reviews the scientific principles that underpin the clinical application of contact lenses
- New chapter on daily disposable contact lenses.
- Contributing authors comprising optometrists, ophthalmologists, dispensing opticians, industry experts, researchers and clinicians – all of whom are true international leaders in their sub-specialty areas.
- Many new line diagrams and clinical photographs to illustrate, inform and explain the concepts outlined in the text.
- Special consideration is given to the most popular lens replacement systems – daily, two-weekly and monthly.
- Extensive appendices to assist chair-side decision making in everyday practice.
- Efron Grading Scales for Contact Lens Complications.
- Evidence-based approach with numerous up-to-date references at the end of each chapter.
Table of Contents
| Section Title | Page | Action | Price |
|---|---|---|---|
| Front cover | cover | ||
| Half title page | i | ||
| Contact Lens Practice | iii | ||
| Copyright page | iv | ||
| Table of Contents | v | ||
| Contributing authors | ix | ||
| Preface to the Second Edition | xi | ||
| Acknowledgements | xiii | ||
| I Introduction | 1 | ||
| 1 Historical perspective | 3 | ||
| Introduction | 3 | ||
| Early theories (1508–1887) | 3 | ||
| Glass scleral lenses (1888) | 4 | ||
| Plastic scleral lenses (1936) | 5 | ||
| Plastic corneal lenses (1948) | 5 | ||
| Silicone elastomer lenses (1965) | 5 | ||
| Soft lenses (1972) | 6 | ||
| Rigid gas-permeable lenses (1974) | 6 | ||
| Disposable lenses (1988) | 6 | ||
| Daily disposable lenses (1994) | 7 | ||
| Silicone hydrogel lenses (1998) | 7 | ||
| The future | 7 | ||
| References | 8 | ||
| 2 The anterior eye | 10 | ||
| Introduction | 10 | ||
| The cornea | 10 | ||
| Corneal anatomy | 10 | ||
| Gross anatomy | 10 | ||
| Microscopic anatomy | 10 | ||
| Epithelium | 10 | ||
| Basal lamina and Bowman’s layer | 11 | ||
| Stroma | 12 | ||
| Descemet’s membrane | 13 | ||
| Endothelium | 13 | ||
| Corneal innervation | 14 | ||
| Source and distribution of corneal nerves | 14 | ||
| Functional considerations | 14 | ||
| Corneal metabolism | 15 | ||
| Source of oxygen and nutrients | 15 | ||
| Oxidative metabolism | 15 | ||
| Corneal transparency | 16 | ||
| Stromal organization | 16 | ||
| Hydration control | 16 | ||
| Response to oedema | 17 | ||
| Corneal epithelial wound healing | 17 | ||
| The ocular adnexa | 17 | ||
| Eyelids | 17 | ||
| Gross anatomy | 17 | ||
| Muscles of the eyelids | 18 | ||
| Orbicularis oculi | 18 | ||
| Levator palpebrae superioris | 18 | ||
| Superior and inferior tarsal muscles (of Müller) | 19 | ||
| Control of eyelid movements | 19 | ||
| Microscopic anatomy | 19 | ||
| Glands of the eyelids | 20 | ||
| Meibomian glands | 20 | ||
| Glands of Zeis and Moll | 20 | ||
| Blood and nerve supply | 20 | ||
| Nerves of the eyelids | 20 | ||
| Blood and lymphatic supply to the eyelids | 20 | ||
| The conjunctiva | 20 | ||
| Gross anatomy | 20 | ||
| Microscopic anatomy | 21 | ||
| Epithelium | 21 | ||
| Goblet and other secretory cells | 22 | ||
| Conjunctival stroma | 22 | ||
| Innervation and blood supply | 22 | ||
| Nerves | 22 | ||
| Blood vessels and lymphatics | 23 | ||
| Functional considerations | 23 | ||
| Lacrimal system | 23 | ||
| Lacrimal gland | 23 | ||
| Gross anatomy | 23 | ||
| Microscopic anatomy | 23 | ||
| Blood and nerve supply | 24 | ||
| Accessory lacrimal glands | 24 | ||
| Functional considerations | 24 | ||
| Lacrimal drainage system | 24 | ||
| The preocular tear film | 25 | ||
| Function and properties of the preocular tear film | 25 | ||
| Tear production | 25 | ||
| Sources and composition | 26 | ||
| Electrolytes | 26 | ||
| Proteins | 26 | ||
| Mucins | 26 | ||
| Lipids | 27 | ||
| Models of tear film structure | 27 | ||
| Conclusions | 28 | ||
| References | 28 | ||
| 3 Visual optics | 30 | ||
| Introduction | 30 | ||
| The basic optics of the eye and ametropia | 30 | ||
| General optical characteristics | 30 | ||
| Model eyes and ametropia | 30 | ||
| Accommodation and the precision of ocular focus | 31 | ||
| Corneal topography | 32 | ||
| Pupil diameter and retinal blur circles | 33 | ||
| Effects of diffraction and aberration | 34 | ||
| Diffraction | 34 | ||
| Monochromatic aberrations | 35 | ||
| Chromatic aberration | 37 | ||
| Overall optical performance of the eye in white light | 38 | ||
| Ocular depth of focus | 38 | ||
| Correction of higher-order ocular aberration | 39 | ||
| Effectivity, spectacle magnification, accommodation and convergence effects with contact lens and spectacle corrections | 40 | ||
| Effectivity | 41 | ||
| Spectacle magnification | 41 | ||
| Accommodation demand | 42 | ||
| Convergence demand | 43 | ||
| Other optical effects | 43 | ||
| Fields of view and fixation | 43 | ||
| Apparent size of the eyes | 44 | ||
| Summary | 44 | ||
| References | 44 | ||
| 4 Clinical instruments | 47 | ||
| Introduction | 47 | ||
| Observation of the eye | 47 | ||
| Burton lamp | 47 | ||
| Non-invasive examination of the tear film | 47 | ||
| Tear morphology | 47 | ||
| Tear break-up | 47 | ||
| Osmometry | 48 | ||
| Tear meniscus height | 48 | ||
| Slit-lamp biomicroscopy | 49 | ||
| Illumination system | 50 | ||
| The microscope | 51 | ||
| High-powered microscopy | 51 | ||
| Specular microscopy | 51 | ||
| Confocal microscopy | 52 | ||
| Tandem scanning confocal microscopy | 52 | ||
| Slit scanning confocal microscopy | 52 | ||
| Confocal microscopy through focusing | 52 | ||
| Rostock cornea module on HRT II | 54 | ||
| Measurement of corneal sensitivity | 54 | ||
| Contact aesthesiometry | 54 | ||
| Non-contact aesthesiometry | 54 | ||
| Assessment of corneal shape | 55 | ||
| Keratometry | 55 | ||
| Corneal topographic analysis | 55 | ||
| Reflective devices | 56 | ||
| Qualitative assessment | 56 | ||
| Quantitative assessment | 56 | ||
| Slit-scanning devices | 57 | ||
| Determination of corneal thickness | 58 | ||
| Pachymetry | 58 | ||
| Optical pachymetry | 58 | ||
| Ultrasonic pachymetry | 59 | ||
| Optical coherence tomography | 59 | ||
| Confocal microscopy | 61 | ||
| Orbscan | 61 | ||
| Conclusions | 61 | ||
| Acknowledgements | 61 | ||
| References | 61 | ||
| II Soft contact lenses | 65 | ||
| 5 Soft lens materials | 67 | ||
| Introduction | 67 | ||
| Polymers | 67 | ||
| The structure of polymers | 68 | ||
| Polymerization | 69 | ||
| Chain polymerization | 69 | ||
| Initiation | 69 | ||
| Propagation | 70 | ||
| Termination | 70 | ||
| Properties of hydrogel materials | 70 | ||
| Optical transparency | 70 | ||
| Mechanical properties | 70 | ||
| Surface properties | 72 | ||
| Water content | 73 | ||
| Oxygen permeability | 73 | ||
| Fluid and ion permeability | 74 | ||
| Refractive index | 74 | ||
| Swell factor and dimensional stability | 74 | ||
| Hydrogel materials | 75 | ||
| Conventional hydrogel materials | 75 | ||
| Silicone hydrogel materials | 77 | ||
| Classification of soft lens materials | 82 | ||
| Conclusion | 82 | ||
| Acknowledgements | 82 | ||
| References | 82 | ||
| Appendix 5.1 Classification of soft lens materials | 84 | ||
| Food and Drug Administration (FDA) classification system | 84 | ||
| Association of Contact Lens Manufacturers (ACLM) classification system | 84 | ||
| BS EN ISO 18369-1: 2006 | 84 | ||
| Example | 85 | ||
| 6 Soft lens manufacture | 86 | ||
| Introduction | 86 | ||
| Methods of manufacture | 86 | ||
| Lathe cutting | 86 | ||
| Spin casting | 88 | ||
| Cast moulding | 88 | ||
| Reproducibility and quality of mass-produced lenses | 90 | ||
| Edge defects | 90 | ||
| Non-edge (body) defects | 90 | ||
| Conclusion | 92 | ||
| References | 92 | ||
| 7 Soft lens optics | 93 | ||
| Introduction | 93 | ||
| On-eye power changes | 93 | ||
| Aberration | 94 | ||
| Conclusion | 97 | ||
| References | 97 | ||
| 8 Soft lens measurement | 100 | ||
| Introduction | 100 | ||
| Back optic zone radius | 100 | ||
| Keratometry | 100 | ||
| Radiuscopy | 101 | ||
| Profile matching | 101 | ||
| The ‘sag’ method | 101 | ||
| Interferometry | 102 | ||
| Optical interferometry | 102 | ||
| Geometric interferometry | 102 | ||
| Overall diameter, optic zones, edge profile and surface quality | 103 | ||
| Back vertex power | 104 | ||
| Water content | 105 | ||
| Thickness | 106 | ||
| Surface wettability | 107 | ||
| Conclusion | 107 | ||
| References | 108 | ||
| 9 Soft lens design and fitting | 109 | ||
| Introduction | 109 | ||
| Ocular measurement | 109 | ||
| Basic principles | 109 | ||
| Forces acting on a soft lens | 109 | ||
| Ideal soft lens fit | 110 | ||
| Soft lens design | 110 | ||
| Lens material and water content | 110 | ||
| Method of manufacture | 111 | ||
| Back optic zone radius | 111 | ||
| Total diameter | 111 | ||
| Back vertex power | 111 | ||
| Centre and edge thickness | 111 | ||
| Soft lens fitting options | 112 | ||
| Trial lens fitting | 112 | ||
| Initial lens selection | 112 | ||
| Soft lens insertion | 112 | ||
| Soft lens removal | 113 | ||
| Settling time | 113 | ||
| Lens fit characteristics | 113 | ||
| Optimum soft lens fit | 113 | ||
| Tight soft lens fit | 114 | ||
| Loose soft lens fit | 114 | ||
| Assessment of fit | 114 | ||
| Comfort | 114 | ||
| Centration | 114 | ||
| Movement | 114 | ||
| Tightness on push-up | 115 | ||
| Peripheral fit | 115 | ||
| Vision | 116 | ||
| Other methods of fit assessment | 116 | ||
| Soft lens fitting problems | 116 | ||
| Discomfort | 116 | ||
| Inappropriate diameter | 116 | ||
| Too large | 116 | ||
| Too small | 117 | ||
| Inappropriate fit | 117 | ||
| Too loose | 117 | ||
| Too tight | 117 | ||
| Poor vision | 117 | ||
| Variable vision | 117 | ||
| Conclusions | 117 | ||
| References | 117 | ||
| 10 Soft toric lens design and fitting | 119 | ||
| Introduction | 119 | ||
| Criteria for use of soft toric lenses | 119 | ||
| Degree of astigmatism | 119 | ||
| Cylinder axis | 119 | ||
| Ocular dominance | 119 | ||
| Viability of other alternatives | 119 | ||
| Visual needs of the patient | 119 | ||
| Design of soft toric lenses | 120 | ||
| Surface optics | 120 | ||
| Stabilization techniques | 120 | ||
| Toroidal back surface | 120 | ||
| Prism ballast | 120 | ||
| Peri-ballast | 120 | ||
| Truncation | 120 | ||
| Dynamic stabilization | 121 | ||
| Principles of correction | 122 | ||
| Fitting | 122 | ||
| Back vertex power determination | 122 | ||
| Effect of lens rotation | 122 | ||
| Predicting lens rotation | 122 | ||
| Lid anatomy | 122 | ||
| Lens–eye relationship | 122 | ||
| Lens thickness profile | 123 | ||
| Allowing for lens rotation | 123 | ||
| Measurement of lens rotation | 123 | ||
| Determining lens misalignment | 124 | ||
| Planned replacement of soft toric lenses | 125 | ||
| Limitations of toric soft lenses | 126 | ||
| Low spherical components | 126 | ||
| Oblique cylinders | 126 | ||
| Large cylindrical components | 126 | ||
| Irregular astigmatism | 126 | ||
| Physiological considerations | 126 | ||
| Conclusions | 126 | ||
| References | 126 | ||
| 11 Soft lens care systems | 128 | ||
| Introduction | 128 | ||
| A rationale for disinfecting contact lenses | 128 | ||
| A rationale for cleaning contact lenses | 128 | ||
| The evolution of soft lens care systems | 129 | ||
| Lens care systems | 129 | ||
| Physical methods | 129 | ||
| Chlorhexidine and thiomersal preserved systems | 130 | ||
| Chlorine | 131 | ||
| Hydrogen peroxide | 131 | ||
| Lens cleaning | 133 | ||
| Multipurpose solutions | 134 | ||
| Polyhexanide-based MPS | 134 | ||
| Polyquaternium-1-based MPS | 134 | ||
| Multipurpose solutions and silicone hydrogel lenses | 135 | ||
| Rewetting solutions | 136 | ||
| Saline solutions | 137 | ||
| Relative performance measures | 137 | ||
| The lens storage case | 139 | ||
| Conclusions | 139 | ||
| References | 139 | ||
| III Rigid contact lenses | 143 | ||
| 12 Rigid lens materials | 145 | ||
| Introduction | 145 | ||
| Poly(methyl methacrylate) | 145 | ||
| The need for oxygen | 145 | ||
| The problem of hydrophobic surfaces | 146 | ||
| The search for better materials | 146 | ||
| Hybrid rigid gas-permeable materials | 146 | ||
| The Gaylord patents – harnessing silicon | 147 | ||
| Commercial rigid materials and their properties | 149 | ||
| Oxygen permeability | 149 | ||
| Mechanical properties | 152 | ||
| Flexure | 152 | ||
| Hardness | 152 | ||
| Surface properties | 152 | ||
| Refractive index | 153 | ||
| Conclusions | 153 | ||
| References | 153 | ||
| 13 Rigid lens manufacture | 154 | ||
| Introduction | 154 | ||
| Rigid lens manufacture | 154 | ||
| Raw materials | 154 | ||
| Generating the lens back surface | 155 | ||
| Generating the lens front surface | 155 | ||
| Engraving, marking and fenestration | 155 | ||
| Edge polishing and final inspection | 157 | ||
| Specialty rigid lens manufacture | 159 | ||
| Toric rigid lens manufacture | 159 | ||
| Aspheric rigid lens manufacture | 160 | ||
| Reverse-geometry lens manufacture | 160 | ||
| Industry regulation | 160 | ||
| Conclusions | 160 | ||
| Acknowledgements | 160 | ||
| References | 161 | ||
| 14 Rigid lens optics | 162 | ||
| Introduction | 162 | ||
| Basic tear lens properties | 162 | ||
| The tear lens during trial lens fits | 162 | ||
| Required BVP when the lens to be ordered has a different BOZR from the trial lens used | 163 | ||
| Calculation of required surface radii from a trial lens fit | 164 | ||
| Neutralization of corneal astigmatism by a rigid lens of spherical power | 164 | ||
| Aberrations of rigid contact lenses | 165 | ||
| Other rigid lens effects | 166 | ||
| Prismatic effects due to decentred or tilted lenses | 166 | ||
| Flexure effects with rigid corneal lenses | 166 | ||
| Visually disturbing effects with rigid lenses | 166 | ||
| Conclusion | 167 | ||
| References | 167 | ||
| 15 Rigid lens measurement | 168 | ||
| Introduction | 168 | ||
| Surface radius | 168 | ||
| Radiuscope | 168 | ||
| Keratometer | 169 | ||
| Diameter | 170 | ||
| Back vertex power | 170 | ||
| Thickness | 171 | ||
| Lens edge | 172 | ||
| Profile | 172 | ||
| Edge lift | 172 | ||
| Lens surface | 173 | ||
| Surface quality | 173 | ||
| Surface wetting | 173 | ||
| Flexibility | 173 | ||
| Material | 174 | ||
| Refractive index | 174 | ||
| Specific gravity | 174 | ||
| Tint | 174 | ||
| Conclusion | 174 | ||
| References | 175 | ||
| 16 Rigid lens design and fitting | 176 | ||
| Introduction | 176 | ||
| Ocular topography | 176 | ||
| Cornea | 176 | ||
| Lids | 177 | ||
| Ethnic variations in ocular dimensions | 177 | ||
| Forces acting on the rigid lens | 177 | ||
| Rigid lens design | 177 | ||
| Back optic zone diameter | 177 | ||
| Front optic zone diameter | 178 | ||
| Centre thickness | 178 | ||
| Edge lift and edge clearance | 178 | ||
| Edge form | 179 | ||
| Spherical versus aspheric designs | 179 | ||
| Spherical designs | 179 | ||
| Aspheric designs | 180 | ||
| PMMA versus RGP lens design | 180 | ||
| Trial fitting options | 180 | ||
| Trial fitting set | 180 | ||
| Empirical fitting | 180 | ||
| Videokeratoscopic fitting | 181 | ||
| Selection of initial lenses | 181 | ||
| Trial fitting set | 181 | ||
| Empirical fitting | 181 | ||
| Lens insertion, removal and settling | 182 | ||
| Lens insertion | 182 | ||
| Lens removal | 182 | ||
| Settling time | 183 | ||
| Lens fit characteristics | 183 | ||
| Optimum lens fit | 183 | ||
| Satisfactory lens fit | 183 | ||
| Assessment of lens fit | 184 | ||
| White light assessment of fit | 184 | ||
| Diameter | 184 | ||
| Centration | 184 | ||
| Movement | 184 | ||
| Peripheral fit | 185 | ||
| Fluorescein assessment of fit | 185 | ||
| Interpretation of fluorescence | 185 | ||
| Fluorescein instillation | 185 | ||
| Central fit | 185 | ||
| Mid peripheral fit | 186 | ||
| Edge fit | 186 | ||
| Overrefraction | 186 | ||
| Rigid lens fitting problems | 186 | ||
| Decentration | 186 | ||
| Peripheral corneal desiccation | 187 | ||
| Peripheral corneal mechanical trauma | 187 | ||
| Discomfort | 188 | ||
| Poor or unstable vision | 188 | ||
| Lens loss | 188 | ||
| Conclusion | 188 | ||
| References | 188 | ||
| 17 Rigid toric lens design and fitting | 190 | ||
| Introduction | 190 | ||
| Forms of toric lens | 190 | ||
| Criteria for use | 190 | ||
| Design considerations | 191 | ||
| Optical considerations | 192 | ||
| Refraction | 192 | ||
| Residual astigmatism | 193 | ||
| Induced astigmatism | 193 | ||
| Spherical power equivalent (‘compensated’) bitoric lenses | 194 | ||
| Cylindrical power equivalent toric lenses | 194 | ||
| Alignment bitoric lenses | 194 | ||
| Back surface toric lenses | 194 | ||
| Front surface toric lenses | 195 | ||
| Oblique bitoric lenses | 195 | ||
| Effect of lens rotation | 195 | ||
| Conclusions | 196 | ||
| References | 196 | ||
| 18 Rigid lens care systems | 197 | ||
| Introduction | 197 | ||
| Disinfection and wetting solutions | 197 | ||
| Cleaning solutions | 197 | ||
| Protein removal solutions | 197 | ||
| Disinfection of trial lens sets | 198 | ||
| Conclusions | 199 | ||
| References | 199 | ||
| IV Lens replacement modalities | 201 | ||
| 19 Unplanned lens replacement | 203 | ||
| Introduction | 203 | ||
| Long-term changes in lenses that are not replaced on a planned basis | 203 | ||
| Lens deposits | 203 | ||
| Irreversible water loss | 205 | ||
| Surface damage and crazing | 206 | ||
| Storage contamination | 206 | ||
| Ocular ramifications of non-planned lens replacement | 207 | ||
| Discomfort | 207 | ||
| Reduced vision | 207 | ||
| Ocular surface pathology | 207 | ||
| Conclusions | 208 | ||
| References | 208 | ||
| 20 Daily soft lens replacement | 209 | ||
| Introduction | 209 | ||
| Patterns of wear | 209 | ||
| Clinical benefits | 210 | ||
| Advantages from the perspective of practitioners | 211 | ||
| Advantages from the perspective of lens wearers | 212 | ||
| Disadvantages | 212 | ||
| Comfort enhancement strategies | 212 | ||
| Manufacturing reliability | 213 | ||
| Environmental impact | 214 | ||
| Limitations to more general acceptance | 214 | ||
| Corneal infiltrative events and keratitis | 214 | ||
| Conclusions | 215 | ||
| Acknowledgements | 215 | ||
| References | 215 | ||
| 21 Planned soft lens replacement | 217 | ||
| Introduction | 217 | ||
| Advantages of planned replacement | 217 | ||
| Use of higher-water-content hydrogel materials | 218 | ||
| Use of silicone hydrogel materials | 218 | ||
| Simple lens care regimes | 218 | ||
| Ready availability of replacement lenses | 219 | ||
| Enhanced compliance with aftercare schedules | 219 | ||
| Single-use trial lenses | 219 | ||
| Trial lens fitting with accurate prescription | 220 | ||
| Lens parameters easy to change | 220 | ||
| Potential disadvantages of planned replacement | 220 | ||
| Patient non-compliance | 220 | ||
| Quality and reproducibility issues | 220 | ||
| Determining the appropriate lens replacement frequency | 221 | ||
| Practice management issues relating to planned soft lens replacement | 221 | ||
| Lens delivery systems | 221 | ||
| Manufacturer-driven systems | 221 | ||
| Practice-driven systems | 221 | ||
| Lenses available for planned replacement | 222 | ||
| Practice logistics | 222 | ||
| Cost to the patient | 223 | ||
| Financial management | 223 | ||
| Alternative supply routes | 223 | ||
| Conclusions | 224 | ||
| Acknowledgements | 224 | ||
| References | 224 | ||
| 22 Planned rigid lens replacement | 225 | ||
| Introduction | 225 | ||
| Life expectancy of rigid contact lenses | 225 | ||
| Regular replacement of rigid lenses | 226 | ||
| Advantages of regular replacement of rigid lenses | 226 | ||
| Daily wear | 226 | ||
| Extended wear | 227 | ||
| Lens binding | 228 | ||
| Optimum replacement schedule | 228 | ||
| Clinical data | 228 | ||
| Theoretical model | 228 | ||
| Planned replacement schemes available | 228 | ||
| Conclusions | 229 | ||
| References | 229 | ||
| V Special lenses and fitting considerations | 231 | ||
| 23 Scleral lenses | 233 | ||
| Introduction | 233 | ||
| Advantages and disadvantages of scleral lenses | 233 | ||
| Indications for scleral lenses | 233 | ||
| Fitting principles | 234 | ||
| Non-ventilated preformed scleral lenses | 234 | ||
| The scleral zone | 235 | ||
| Optic zone sagittal depth and optic zone projection | 235 | ||
| Non-coaxial scleral lenses | 238 | ||
| Toroidal lenses | 238 | ||
| Impression moulding | 238 | ||
| Fenestrated lenses | 238 | ||
| Modification | 238 | ||
| Ordering scleral lenses | 238 | ||
| Lens hygiene and maintenance | 239 | ||
| Storage | 239 | ||
| Cleaning and conditioning | 239 | ||
| Saline for filling non-ventilated RGP scleral lenses | 239 | ||
| Rewetting | 239 | ||
| Problems and complications with scleral lens wear | 239 | ||
| Discomfort | 239 | ||
| Bubbles | 239 | ||
| Accumulation of mucus | 240 | ||
| Conjunctival blanching and hyperaemia | 240 | ||
| Conjunctival displacement over the limbus | 240 | ||
| Degradation of the surface | 240 | ||
| Infection | 240 | ||
| Giant papillary conjunctivitis | 240 | ||
| Hypoxia | 240 | ||
| Neovascularization | 240 | ||
| Neovascularization in keratoconus | 241 | ||
| Conclusion | 241 | ||
| Acknowledgement | 241 | ||
| References | 241 | ||
| 24 Tinted lenses | 243 | ||
| Introduction | 243 | ||
| Basic options | 243 | ||
| Tinted lens designs and applications | 243 | ||
| Handling tints | 243 | ||
| Cosmetic tinted lenses | 244 | ||
| Prosthetic tinted lenses | 244 | ||
| Therapeutic tinted lenses | 244 | ||
| Performance-enhancing tinted lenses | 245 | ||
| Colour vision | 245 | ||
| Dyslexia | 245 | ||
| Sport | 245 | ||
| Prophylactic tints | 246 | ||
| Theatric tinted lenses | 246 | ||
| Identification tints | 247 | ||
| Manufacture | 247 | ||
| Translucent tints | 247 | ||
| Dye dispersion tinting | 247 | ||
| Vat dye tinting | 247 | ||
| Chemical bond tinting | 248 | ||
| Printing | 248 | ||
| Opaque tints | 248 | ||
| Dot matrix printing | 248 | ||
| Laminate constructions | 248 | ||
| Opaque backing | 249 | ||
| Clinical considerations | 249 | ||
| Tint distribution | 249 | ||
| Lens fitting | 250 | ||
| Lens maintenance | 250 | ||
| Oxygen transmissibility | 250 | ||
| Visual effects | 250 | ||
| Replacement frequency | 250 | ||
| Care of multiple pairs | 250 | ||
| Lens deposits | 250 | ||
| Discomfort and dryness | 250 | ||
| Conclusions | 250 | ||
| References | 250 | ||
| 25 Presbyopia | 252 | ||
| Introduction | 252 | ||
| Patient selection | 252 | ||
| Patient expectations | 253 | ||
| Initial measurements | 254 | ||
| Monovision | 254 | ||
| General principles of monovision fitting | 255 | ||
| Partial monovision | 255 | ||
| Enhanced monovision | 255 | ||
| Modified monovision | 255 | ||
| Bifocal and multifocal contact lenses | 255 | ||
| Simultaneous-vision designs | 256 | ||
| Biconcentric designs | 257 | ||
| Multizone concentric designs | 257 | ||
| Modified monovision multizone concentric designs | 258 | ||
| Diffractive designs | 258 | ||
| Aspheric designs | 259 | ||
| Back surface aspheric designs | 259 | ||
| Front surface aspheric designs | 259 | ||
| Zonal aspheric design | 259 | ||
| Lens fitting | 259 | ||
| Lens adjustments | 260 | ||
| Alternating (translating)-vision designs | 261 | ||
| General principles of lens designs | 261 | ||
| Solid design | 261 | ||
| Fused design | 262 | ||
| Lens fitting | 262 | ||
| Conclusions | 263 | ||
| Acknowledgements | 265 | ||
| References | 265 | ||
| 26 Continuous wear | 266 | ||
| Introduction | 266 | ||
| Experiences with extended wear | 266 | ||
| Conventional soft extended wear | 266 | ||
| Non-hydrophilic materials | 267 | ||
| Disposable soft lenses | 267 | ||
| Silicone-containing hydrogel contact lenses | 268 | ||
| Mechanisms of adverse effects in extended wear | 268 | ||
| Acute physiological effects | 268 | ||
| The role of hypoxia | 270 | ||
| Chronic physiological changes | 272 | ||
| Mechanical effects | 274 | ||
| Non-infectious inflammatory events | 275 | ||
| Infectious corneal ulceration | 276 | ||
| Clinical extended-wear practice | 276 | ||
| Is extended wear safe? | 276 | ||
| Application of continuous wear in practice | 277 | ||
| Managing extended-wear complications | 277 | ||
| Acute responses | 278 | ||
| Chronic physiological stress | 278 | ||
| Microbial keratitis | 278 | ||
| Papillary conjunctivitis | 279 | ||
| Superior epithelial arcuate lesions | 279 | ||
| Conclusions | 279 | ||
| References | 279 | ||
| 27 Sport | 281 | ||
| Introduction | 281 | ||
| Deciding on the best form of correction | 281 | ||
| Refractive surgery | 281 | ||
| Do contact lenses enhance sporting performance? | 281 | ||
| Environmental and physical constraints | 282 | ||
| Environmental conditions | 282 | ||
| Cold | 282 | ||
| Altitude | 282 | ||
| Dirt and dust | 283 | ||
| Aquatic environments | 283 | ||
| Subaquatic environments | 284 | ||
| Ultraviolet light | 284 | ||
| Physical conditions | 284 | ||
| Extreme body movements | 284 | ||
| Body contact | 284 | ||
| Airflow | 284 | ||
| Gravitational forces | 285 | ||
| General considerations | 285 | ||
| Conclusions | 285 | ||
| References | 286 | ||
| 28 Keratoconus | 287 | ||
| Introduction | 287 | ||
| Demographics of keratoconus | 287 | ||
| Management options | 287 | ||
| Spectacle correction | 287 | ||
| Soft lenses | 288 | ||
| Hybrid lenses | 289 | ||
| Rigid contact lens correction | 289 | ||
| Scleral lenses | 289 | ||
| Surgical management | 289 | ||
| Most suitable rigid lens types | 290 | ||
| Fitting philosophies and fluorescein patterns | 291 | ||
| Apical touch versus apical clearance | 291 | ||
| Lens fitting protocols | 292 | ||
| Rigid lens fitting procedure | 293 | ||
| Keratometry | 293 | ||
| Refraction | 293 | ||
| Trial lens fitting | 293 | ||
| Fluorescein pattern analysis | 293 | ||
| CLEK study fitting protocol | 294 | ||
| Criteria for referral for evaluation for keratoplasty | 294 | ||
| Conclusion | 296 | ||
| Reference | 296 | ||
| 29 High ametropia | 298 | ||
| Introduction | 298 | ||
| Lens materials for high ametropia | 298 | ||
| Silicone elastomer | 298 | ||
| Silicone hydrogel | 298 | ||
| Principles of high-power lens design | 299 | ||
| High-plus | 299 | ||
| Aphakia | 299 | ||
| High-minus | 300 | ||
| High astigmatism | 300 | ||
| Fitting challenges | 301 | ||
| Low vision | 301 | ||
| Conclusions | 301 | ||
| References | 302 | ||
| 30 Paediatric fitting | 303 | ||
| Introduction | 303 | ||
| Indications | 303 | ||
| Aphakia | 303 | ||
| Pseudophakia | 303 | ||
| Myopia | 304 | ||
| Ocular motility disorders | 305 | ||
| Irregular astigmatism | 305 | ||
| Tinted and prosthetic lenses | 305 | ||
| Therapeutic lenses | 305 | ||
| Ocular response to lens wear | 305 | ||
| Examination techniques | 305 | ||
| Anterior-segment examination | 305 | ||
| Keratometry | 306 | ||
| Refraction | 306 | ||
| Biometry | 306 | ||
| Lens selection | 306 | ||
| Hydrogel lenses | 306 | ||
| Silicone hydrogel lenses | 306 | ||
| Silicone rubber lenses | 307 | ||
| Rigid lenses | 307 | ||
| Handling of lenses | 307 | ||
| Common aftercare problems | 307 | ||
| Acknowledgement | 308 | ||
| References | 308 | ||
| 31 Therapeutic applications | 310 | ||
| Introduction | 310 | ||
| Indications | 310 | ||
| Unusual or distorted corneal shape | 310 | ||
| Relief of pain | 310 | ||
| Recurrent erosion syndrome | 310 | ||
| Corneal dystrophies involving the epithelium | 310 | ||
| Filamentary keratitis | 311 | ||
| Corneal degenerations involving the epithelium | 311 | ||
| Chemical injuries | 311 | ||
| Cicatricial conjunctivitis | 312 | ||
| Tear deficiency | 312 | ||
| Protection from lids and environment | 312 | ||
| Maintenance of a precorneal tear reservoir | 313 | ||
| Following trauma or surgery | 313 | ||
| Following spontaneous perforation | 313 | ||
| Lens types | 313 | ||
| Soft hydrogel and silicone hydrogel lenses | 313 | ||
| Rigid lenses | 314 | ||
| Scleral lenses | 314 | ||
| Concurrent medication | 315 | ||
| Drug delivery | 315 | ||
| Complications | 315 | ||
| Conclusions | 316 | ||
| References | 316 | ||
| 32 Post-refractive surgery | 317 | ||
| Introduction | 317 | ||
| Types of refractive surgery | 317 | ||
| Contact lens fitting following radial keratotomy | 317 | ||
| Corneal topography | 317 | ||
| Rigid lenses | 317 | ||
| Soft lenses | 318 | ||
| Contact lens fitting following photorefractive procedures | 318 | ||
| Tissue ablation and corneal topography | 319 | ||
| Rigid lens designs | 319 | ||
| Reverse-geometry rigid lens designs | 320 | ||
| Soft lenses | 320 | ||
| Comparative performance of rigid versus soft lenses | 321 | ||
| Decentred ablations | 321 | ||
| Conclusions | 321 | ||
| References | 321 | ||
| 33 Post-keratoplasty | 322 | ||
| Introduction | 322 | ||
| Indications | 322 | ||
| Types of corneal graft | 322 | ||
| Corneal topography following PKP | 324 | ||
| Suture techniques for PKP | 324 | ||
| Indications and contraindications for contact lens wear post corneal grafts | 325 | ||
| General concerns | 326 | ||
| Lens fitting techniques | 326 | ||
| Continuing care and complications | 327 | ||
| Graft rejection and failure | 328 | ||
| Epithelial rejection | 328 | ||
| Stromal rejection | 328 | ||
| Endothelial rejection | 328 | ||
| Graft failure | 328 | ||
| Other management issues | 328 | ||
| Contact lens results | 329 | ||
| Conclusions | 329 | ||
| Acknowledgement | 329 | ||
| References | 329 | ||
| 34 Orthokeratology | 332 | ||
| Introduction | 332 | ||
| Outcomes of earlier techniques | 332 | ||
| Independent studies | 332 | ||
| Modern orthokeratology | 333 | ||
| Reverse-geometry lenses | 333 | ||
| Indications and contraindications | 333 | ||
| Outcomes of accelerated orthokeratology | 334 | ||
| Efficacy | 334 | ||
| Regression | 335 | ||
| Safety | 335 | ||
| How orthokeratology works | 336 | ||
| Determinants of success | 336 | ||
| Correction of hyperopia | 337 | ||
| Control of myopia progression in children | 337 | ||
| Correlations | 337 | ||
| Conclusions | 337 | ||
| Is orthokeratology effective in modifying refractive errors? | 337 | ||
| Is orthokeratology safe? | 337 | ||
| Is orthokeratology clinically efficacious? | 337 | ||
| Acknowledgement | 338 | ||
| References | 338 | ||
| 35 Diabetes | 339 | ||
| Introduction | 339 | ||
| The anterior eye | 339 | ||
| Orbit | 339 | ||
| Eyelids | 339 | ||
| Tear film | 339 | ||
| Conjunctiva | 339 | ||
| Iris | 339 | ||
| Pupil | 340 | ||
| Cornea | 340 | ||
| Epithelium | 340 | ||
| Corneal nerves | 340 | ||
| Endothelium | 341 | ||
| Corneal hydration control | 341 | ||
| Microbial keratitis | 341 | ||
| Panretinal photocoagulation | 341 | ||
| Ocular response to contact lenses | 341 | ||
| Special considerations | 342 | ||
| Prescribing contact lenses | 342 | ||
| Compliance | 342 | ||
| Contact lens wear in patients with other systemic disease | 342 | ||
| Corneal scarring or thinning | 342 | ||
| Keratoconjunctivitis sicca | 342 | ||
| Handling problems | 342 | ||
| Ocular side-effects of therapy | 343 | ||
| Conclusion | 343 | ||
| References | 343 | ||
| VI Patient examination and management | 345 | ||
| 36 History taking | 347 | ||
| Introduction | 347 | ||
| Indications and contraindications for contact lens wear | 347 | ||
| Anatomical | 347 | ||
| Ocular health | 347 | ||
| General health | 348 | ||
| Allergies | 348 | ||
| Chronic infection | 348 | ||
| Metabolic disorders | 348 | ||
| Pregnancy | 348 | ||
| Systemic medication | 348 | ||
| Psychological factors including motivation | 348 | ||
| Lifestyle/occupational issues | 349 | ||
| Financial considerations | 349 | ||
| The case history | 349 | ||
| Non-lens wearers | 349 | ||
| Previous lens wearer | 350 | ||
| Patient education, risk/benefit analysis and informed consent | 350 | ||
| Record keeping | 350 | ||
| Conclusions | 351 | ||
| References | 351 | ||
| 37 Preliminary examination | 352 | ||
| Introduction | 352 | ||
| Measurement of vision | 352 | ||
| Retinoscopy and subjective refraction | 352 | ||
| Anatomical measurements | 352 | ||
| Keratometry | 353 | ||
| Corneal topography | 353 | ||
| Slit-lamp biomicroscopy | 354 | ||
| Diffuse wide beam | 355 | ||
| Direct focal illumination | 355 | ||
| Parallelepiped | 356 | ||
| Optic section | 356 | ||
| Oblique illumination | 356 | ||
| Specular reflection | 356 | ||
| Indirect illumination | 357 | ||
| Sclerotic scatter | 357 | ||
| Retroillumination | 358 | ||
| Fluorescein staining | 358 | ||
| Tear film evaluation | 358 | ||
| Ophthalmoscopy | 359 | ||
| Binocular vision assessment | 359 | ||
| Supplementary tests | 359 | ||
| Corneal sensitivity | 359 | ||
| Visual fields | 359 | ||
| Tonometry | 359 | ||
| Stereopsis | 359 | ||
| Colour vision testing | 359 | ||
| Conclusions | 359 | ||
| References | 360 | ||
| 38 Patient education | 361 | ||
| Introduction | 361 | ||
| Objectives | 361 | ||
| Timing | 361 | ||
| Creating the optimum teaching environment | 361 | ||
| The teaching area | 361 | ||
| Accoutrements | 362 | ||
| Patient instruction | 362 | ||
| Hand grooming and hygiene | 362 | ||
| Lid manipulation | 362 | ||
| Lens inspection | 362 | ||
| Lens application | 363 | ||
| Tips on comfort and lens recentring | 364 | ||
| Lens removal | 365 | ||
| The blink technique | 365 | ||
| The two-handed technique | 365 | ||
| Suction holders | 366 | ||
| Care products | 366 | ||
| Cosmetics | 366 | ||
| Wearing schedules | 366 | ||
| Soft lenses | 367 | ||
| Rigid lenses | 367 | ||
| Recognizing an emergency | 367 | ||
| Patient discharge | 367 | ||
| Informed consent | 367 | ||
| Conclusion | 368 | ||
| References | 368 | ||
| 39 Aftercare | 369 | ||
| Introduction | 369 | ||
| Recommended visit schedules | 369 | ||
| Preparing for the aftercare visit | 370 | ||
| Aftercare procedures while lenses are worn | 370 | ||
| History taking | 370 | ||
| Visual acuity | 371 | ||
| Overrefraction | 371 | ||
| Overkeratometry | 371 | ||
| External examination | 371 | ||
| Slit-lamp biomicroscopy | 371 | ||
| Lens surface assessment | 371 | ||
| Lens fitting characteristics | 373 | ||
| Lens–eye interactions | 373 | ||
| Aftercare procedures following lens removal | 374 | ||
| Uncorrected vision | 374 | ||
| Refraction | 374 | ||
| Keratometry and corneal topography | 374 | ||
| Oblate shape | 375 | ||
| Inferior steepening | 375 | ||
| Impression arcs | 375 | ||
| Posterior corneal elevation | 376 | ||
| Slit-lamp biomicroscopy | 377 | ||
| Lens inspection and verification | 377 | ||
| Additional procedures | 377 | ||
| Pachymetry | 378 | ||
| Corneal endothelial analysis | 378 | ||
| Other tests as required | 378 | ||
| Discussion with patient | 378 | ||
| Grading scales | 378 | ||
| Grading scale design | 378 | ||
| Image size | 379 | ||
| How to grade | 379 | ||
| How to record grading | 379 | ||
| Interpretation of grading | 379 | ||
| Determinants of grading performance | 379 | ||
| General approaches to solving problems | 380 | ||
| Eye redness | 381 | ||
| Characterizing eye redness | 381 | ||
| Strategies for diagnosing and solving eye redness | 381 | ||
| Discomfort | 382 | ||
| Characterizing symptoms of discomfort | 382 | ||
| Strategies for solving symptoms relating to discomfort | 383 | ||
| Poor vision | 384 | ||
| Characterizing symptoms of poor vision | 384 | ||
| Strategies for solving symptoms relating to poor vision | 385 | ||
| Conclusions | 386 | ||
| References | 386 | ||
| 40 Complications | 388 | ||
| Introduction | 388 | ||
| Eyelids | 388 | ||
| Blinking | 388 | ||
| Ptosis | 389 | ||
| Meibomian gland dysfunction | 389 | ||
| Eyelash disorders | 390 | ||
| Tear film | 391 | ||
| Dry eye | 391 | ||
| Mucin balls | 392 | ||
| Conjunctiva | 393 | ||
| Conjunctival staining | 394 | ||
| Conjunctival redness | 394 | ||
| Papillary conjunctivitis | 395 | ||
| Limbus | 396 | ||
| Limbal redness | 396 | ||
| Vascularized limbal keratitis | 397 | ||
| Superior limbic keratoconjunctivitis | 398 | ||
| Corneal epithelium | 399 | ||
| Epithelial staining | 399 | ||
| Microcysts | 400 | ||
| Vacuoles | 401 | ||
| Wrinkling | 401 | ||
| Corneal stroma | 403 | ||
| Oedema | 403 | ||
| Thinning | 404 | ||
| Deep stromal opacities | 404 | ||
| Neovascularization | 406 | ||
| Keratitis | 407 | ||
| Warpage | 408 | ||
| Corneal endothelium | 409 | ||
| Bedewing | 409 | ||
| Blebs | 410 | ||
| Polymegethism | 411 | ||
| Conclusions | 412 | ||
| References | 412 | ||
| 41 Digital imaging | 416 | ||
| Introduction | 416 | ||
| Previous imaging methods | 416 | ||
| Principles of digital imaging | 416 | ||
| Benefits of digital imaging for contact lens practice | 417 | ||
| Examples of digital imaging in contact lens practice | 418 | ||
| Limbal neovascularization | 418 | ||
| Rigid lens fitting | 418 | ||
| Refractive surgery on disposable contact lens wearer | 418 | ||
| Illumination methods for slit-lamp digital imaging | 418 | ||
| Commercial digital imaging systems | 419 | ||
| ‘Build-your-own’ digital imaging system | 419 | ||
| Video slit-lamp imaging system | 421 | ||
| Digital video camera and beam splitter | 421 | ||
| Computer and video digitizer | 422 | ||
| Software for still images | 422 | ||
| Recording digital movies | 422 | ||
| File back-up | 422 | ||
| Printer | 423 | ||
| Digital still camera slit-lamp imaging system | 423 | ||
| Fundus camera | 423 | ||
| OCT anterior segment | 423 | ||
| Other instruments | 423 | ||
| Image editing | 425 | ||
| Conclusion | 425 | ||
| References | 425 | ||
| 42 Compliance | 427 | ||
| Introduction | 427 | ||
| Consequences of non-compliance | 427 | ||
| Extent and pattern of non-compliance | 427 | ||
| Duration of the prescription | 427 | ||
| Erroneous contact lens procedures | 427 | ||
| Compliance with the incorrect prescription | 428 | ||
| Compliance with the correct prescription | 428 | ||
| Investigation of strategies for compliance enhancement | 428 | ||
| Improving initial patient education | 429 | ||
| Periodic self-review | 429 | ||
| Reducing cost | 429 | ||
| Predicting non-compliance | 430 | ||
| A compliance enhancement model | 430 | ||
| The clinic and practitioner | 430 | ||
| The patient | 430 | ||
| The advice | 431 | ||
| The contact lens industry | 431 | ||
| Conclusion | 431 | ||
| References | 431 | ||
| 43 Practice management | 433 | ||
| Introduction | 433 | ||
| Practice location and accommodation | 433 | ||
| Layout | 434 | ||
| Reception area and front desk | 434 | ||
| Waiting area | 434 | ||
| Consulting room | 434 | ||
| Spectacle dispensary | 434 | ||
| Contact lens dispensary | 434 | ||
| Personnel at the practice | 434 | ||
| Recruitment and selection | 434 | ||
| Contract of employment | 435 | ||
| Discipline and dismissal | 435 | ||
| Training staff | 435 | ||
| Products and services provided | 436 | ||
| Pricing – fees and charges | 436 | ||
| Speciality–commodity continuum | 436 | ||
| Professional model | 437 | ||
| Promotional issues | 437 | ||
| Internal | 437 | ||
| External | 437 | ||
| Processes | 437 | ||
| Managing patients | 438 | ||
| Contracts, service agreements and informed consent | 438 | ||
| Patient scheduling | 438 | ||
| Patient education | 438 | ||
| Records on patient web pages | 439 | ||
| Managing contact lens products | 439 | ||
| Managing money | 439 | ||
| Lens ordering | 439 | ||
| Professional regulation | 439 | ||
| Conclusions | 441 | ||
| References | 441 | ||
| Appendices | 443 | ||
| Appendix A Contact lens design and specifications | 444 | ||
| Appendix B Contact lens tolerances | 445 | ||
| Appendix C Vertex distance correction | 446 | ||
| Appendix D Corneal curvature – corneal power conversion | 448 | ||
| Appendix E Extended keratometer range conversion | 450 | ||
| Appendix F Soft lens average thickness | 452 | ||
| Appendix G Soft lens oxygen performance | 453 | ||
| Appendix H Constant edge clearance rigid lens designs | 455 | ||
| Appendix I Soft toric lens misalignment demonstrator | 456 | ||
| Appendix J Dry-eye questionnaire | 457 | ||
| Appendix K Efron grading scales for contact lens complications | 459 | ||
| Index | 463 |