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 |