CONTACT LENSES

The book focuses on the chemistry and properties of contact lenses and their fabrication methods.

With research& development continuing in the field, this comprehensive book takes a look at the last 10 years in terms of new materials, chemistry methods, applications, and fabrication techniques. New applications include drug delivery, lenses for augmented reality, electronic contact lenses, and wearable smart contact lenses.

In addition, the book discusses simulation methods for contact lenses, such as ocular topography parameters, gas permeable lenses, and computerized videokeratography. On the fabrication front, several common fabrication methods for contact lenses are detailed, including the computer-aided contact lens design, methods for the fabrication of colored contact lenses, and the fabrication of decentered contact lenses. Special processes are reviewed, including, mold processes, reactive ion etching, electrospinning, and others. Also discussed are the properties of contact lenses and methods for the measurement. Many of the standard methods are discussed, but other issues are taken up too including a discussion on the assessment of cytotoxic effects, the Schirmer tear test, and others. The book concludes with a chapter detailing the possible medical problems related to contact lenses and how to avoid them. These include eye diseases, allergic and toxic reactions, as well as methods for medical treatment such as disinfection agents.

Audience

The book will be used by chemists, polymer scientists, ophthalmologists, engineers in the contact lens industry as well as polymer industries.

Johannes Karl Fink is Professor of Macromolecular Chemistry at Montanuniversität Leoben, Austria. His industry and academic career spans more than 30 years in the fields of polymers, and his research interests include characterization, flame retardancy, thermodynamics and the degradation of polymers, pyrolysis, and adhesives. Professor Fink has published 20 books on physical chemistry and polymer science with the Wiley-Scrivener imprint, includingA Concise Introduction to Additives for Thermoplastic Polymers,The Chemistry of Bio-based Polymers, 2nd edition,3D Industrial Printing with Polymers,The Chemistry of Environmental Engineering and Flame Retardants.

Preface xi

1 Types of Lenses 1

1.1 History of Contact Lenses 1

1.2 Materials 3

1.3 Monomers 3

1.3.1 Monomers for Block Copolymers 3

1.3.2 Silicone Acrylamides 7

1.4 Soft Lenses 13

1.4.1 Hydrogels 13

1.4.2 PVA Hydrogel 48

1.4.3 Clear Contact Lenses 48

1.5 Water Absorbable Formulations 49

1.6 Bandage Contact Lenses 53

1.6.1 Antimicrobial Bandage Contact Lens 53

1.7 Functional Contact Lenses 56

1.7.1 Remote Health Monitoring 56

1.7.2 Graphene Oxide Nanocolloids 60

1.7.3 Diabetic Diagnosis 61

1.7.4 Target Analyte Sensing 66

1.7.5 Adaptive Tuning 71

1.7.6 Wireless Communication 72

1.7.7 Glucose Biosensors 76

1.7.8 Cancer Detection 78

1.8 Scleral Contact Lenses 78

1.8.1 Fabrication of Scleral Lenses 79

1.8.2 Scleral Lens Fitting 82

1.8.3 Ocular Drug Delivery Systems 83

1.9 Multifocal Contact Lenses 83

1.9.1 Bifocal Contact Lenses 83

1.9.2 Silicone Hydrogels 85

1.9.3 Non-Silicone Hydrogels 89

1.9.4 Tilted-Wear Type Contact Lenses 93

1.9.5 Neutral Density Filters 94

1.10 Augmented Reality Contact Lens Systems 95

1.10.1 Electronic Contact Lenses 96

1.10.2 Smart Contact Lenses 96

1.10.3 Wearable Smart Contact Lenses 97

1.10.4 Collimated Light-Emitting Diodes 98

1.11 Siloxane Macromers 99

1.11.1 Silicone Urethane Polymers 102

1.12 Oxygen-Permeable Lenses 107

1.12.1 Extended Wear Lenses 107

1.12.2 Structures for Thick Payloads 115

1.13 Natural Protein Polymer Contact Lenses 118

1.14 Ultrathin Coating 119

1.15 Anti-Biofouling Contact Lenses 121

1.15.1 Phosphorylcholine 121

1.15.2 2-Hydroxyethyl methacrylate 125

1.15.3 Chitosan 127

1.16 Drug Delivery via Hydrogel Contact Lenses 129

1.16.1 Hydrogels with Phosphate Groups 129

1.16.2 Ophthalmic Drug Delivery 131

1.17 Simulation Methods 133

1.17.1 Ocular Topography Parameters 133

1.17.2 Rigid Gas-Permeable Lenses 134

1.17.3 Computerized Videokeratography 134

References 135

2 Fabrication Methods 149

2.1 Computer-Aided Contact Lens Design and Fabrication 149

2.1.1 Spline-Based Mathematical Surfaces 149

2.1.2 Corneal Refractive Therapy Program 152

2.2 Contact Lenses with Selective Spectral Blocking 154

2.3 Colored Contact Lenses 156

2.3.1 Hard Colored Contact Lenses 157

2.4 Decentered Contact Lenses 161

2.5 Stabilized Contact Lenses 162

2.6 Additive Manufacturing 163

2.7 Mold Process 164

2.7.1 Injection Molding 164

2.7.2 Cast Molding 166

2.7.3 Two-Part Mold Assembly 168

2.8 Reactive Ion Etching 170

2.9 Electrospinning 172

2.9.1 Creating Electrospun Contact Lens Structures 172

2.9.2 Electrospinning Controlled Polymer Fibril Matrices 174

2.9.3 Electrospinning of a Prepolymer Solution 175

2.10 Rigid Plastic Lenses 183

2.10.1 Rigid Gas-Permeable Contact Lenses 183

2.11 Soft Plastic Lenses 184

2.11.1 Layer-by-Layer Deposition 184

2.11.2 Electron-Beam Irradiation Polymerization 191

2.11.3 Shaping and Cutting 192

2.12 Coating Methods 195

2.12.1 Zwitterionic Coating 195

2.12.2 Antibacterial Nanocoating 196

2.13 Disinfection of Contact Lenses 196

2.13.1 Hydrogen Peroxide and Fibrous Catalyst 197

2.13.2 Hydrogen Peroxide and Metal Catalyst 197

2.13.3 Removing Hydrogen Peroxide 199

2.14 Integrated Microtubes 201

2.15. Injection Molding 201

2.15.1 Aspheric Contact Lenses 201

2.16 Handling Tools 202

2.16.1 Insertion Tool 202

2.16.2 Insertion Tool 205

References 205

3 Properties 211

3.1 Ophthalmic Compatibility Requirements 211

3.2 Standards 212

3.2.1 Tensile Properties of Plastics 212

3.2.2 Tear-Propagation Resistance 215

3.2.3 Oxygen Gas Transmission Rate 215

3.2.4 Biomaterials 215

3.2.5 Eye Protectors 216

3.3 Eye Model with Blink Mechanism 217

3.4 Assessment of Cytotoxic Effects 219

3.4.1 Draize Eye Irritation Test 219

3.4.2 Acute Eye Irritation Testing 220

3.4.3 Benzalkonium Chlorides 220

3.4.4 Residual Monomer Content 221

3.5 Special Functions 223

3.5.1 Intraocular Pressure 224

3.5.2 Coating Thickness 229

3.6 Cleaning of Contact Lenses 229

3.7 Biofouling 234

3.8 Wettability 234

3.8.1 Blister Pack Solutions 236

3.8.2 Captive Bubble Method 237

3.8.3 Tethered Hyaluronic Acid-Based Coatings 239

3.9 Material Properties and Antimicrobial Efficacy 240

3.10 Microscopic Examination 242

3.10.1 X-Ray Photoelectron Spectroscopy 243

3.10.2 Atomic Force Spectroscopy 244

3.10.3 Electrochemical Impedance Spectroscopy 246

3.10.4 Scanning Electron Microscopy 247

3.11 Schirmer Tear Test 248

3.12 Ocular Surface Disease Index Test 248

3.13 Corneal Fluorescein Staining Test 249

3.14 Ion Permeability 250

3.14.1 Ionoflux Technique 250

3.14.2 Ionoton Measurement Technique 252

3.15 Hydrodell Water Permeability Technique 253

3.16 Oxygen Permeability and Transmissibility 253

3.16.1 Contact Lens Solutions 254

3.17 Optical Biometer 255

3.17.1 Ophthalmologic Apparatus 255

3.17.2 Ophthalmologic Information Processing 259

3.17.3 Swept-Source Optical Coherence Tomography 259

References 260

4 Drug Delivery 271

4.1 Basic Issues 272

4.2 Methodologies for the Design of Therapeutic Contact Lenses 273

4.2.1 Soaking Method 273

4.2.2 pH-Sensitive Lenses 273

4.2.3 Magnetic Micropump 275

4.2.4 Molecular Imprinting 275

4.2.5 Colloidal Nanoparticles 276

4.2.6 Polymeric Nanoparticles 276

4.2.7 Cyclodextrins 277

4.2.8 Liposomes 277

4.2.9 Microemulsion and Micelles 278

4.2.10 Vitamin E 278

4.2.11 Supercritical Fluid Technology 278

4.2.12 Hydrophobic Drug Loading 279

4.2.13 Cationic Drugs 279

4.3 Hydrogels 281

4.3.1 Salt-Induced Modulation 283

4.3.2 Polymeric Hydrogels 284

4.3.3 Colloid-Laden Hydrogels 285

4.3.4 Ligand-Containing Hydrogels 285

4.3.5 Amphiphilic Polymers 286

4.3.6 Silicone Hydrogel Contact Lenses 289

4.3.7 Zwitterionic Hydrogels 290

4.3.8 Surface-Modified Hydrogels 291

4.3.9 Cyclodextrin-Hyaluronan Hydrogels 293

4.3.10 Bioinspired Hydrogels 293

4.3.11 Tobramycin Release 294

4.4 Contact Lens Gels 297

4.5 Molecularly Imprinted Contact Lenses 298

4.5.1 Molecular Imprinting Technology 298

4.5.2 Molecularly Imprinted Contact Lenses 299

4.5.3 Hydrogels 301

4.5.4 Supercritical Fluid-Assisted Preparation 302

4.6 Special Drugs 303

4.6.1 Timolol 303

4.6.2 Dexamethasone 308

4.6.3 Ketotifen Fumarate 312

4.6.4 Ciprofloxacin 315

4.6.5 Ofloxacin 318

4.6.6 Polymyxin B and Vancomycin 321

4.6.7 Epinastine 323

4.6.8 Lactoferrin 323

4.6.9 Bimatoprost 324

4.6.10 Dipicolylamine 325

4.6.11 Gatifloxacin 326

4.6.12 Hydroxypropyl Methylcellulose 328

4.6.13 Dorzolamide 328

4.6.14 Ethoxzolamide 329

4.6.15 Hyaluronic Acid 331

4.6.16 Lifitegrast 335

4.6.17 Diclofenac Sodium 336

4.6.18 Moxifloxacin 339

4.6.19 Norfloxacin 340

4.6.20 Sparfloxacin 341

4.6.21 Latanoprost 342

4.6.22 Loteprednol 343

4.6.23 Release of Multiple Therapeutics 344

References 347

5 Medical Problems 363

5.1 Eye Diseases 363

5.2 Corneal Edema 363

5.2.1 PMMA Lenses 365

5.2.2 Thickness Changes 365

5.2.3 Corneal Swelling 366

5.2.4 Acanthamoeba Keratitis 367

5.3 Presbyopia and Myopia Control 368

5.4 Toxic Soft Lenses 369

5.4.1 Allergic and Toxic Reactions 370

5.5 Disinfection Agents 374

5.5.1 Polymeric Biguanide and Vinylimidazole 375

5.5.2 Saccharides 376

5.5.3 Amphipathic Peptides 381

5.5.4 Antibacterial Properties 384

5.6 Silicone Hydrogels 385

5.7 Limbal Stem Cell Deficiency 385

5.8 Computer Vision Syndrome 387

5.8.1 Tests and Analysis 388

5.8.2 Pathophysiology 388

5.8.3 Problems for Radiologists 389

5.9 Dry Eye Problems 390

5.9.1 Ions in Tears 390

5.9.2 Treatment Methods 392

5.9.3 Comparative Study of the Reasons for Dry Eyes 394

5.10 Orthokeratology 395

5.10.1 Myopia 398

References 401

Index 413

Acronyms 413

Chemicals 416

General Index 429