Lens and Cataract, Section 11
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CONTENTS
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General Introduction xiii
Objectives for BCSC Section 11 1
Introduction to Section 11 3
I. Anatomy 5
Normal crystalline lens 5
Capsule 7
Zonular fibers 8
Lens epithelium 8
Nucleus and cortex 9
II. Biochemistry 10
Molecular biology 10
Membrane structural proteins and cytoskeletal proteins 11
Increase of water-insoluble proteins with age 11
Decrease in lens protein concentration with age 12
Evolution and the molecular biology of crystallins 12
Carbohydrate metabolism 12
Oxidative damage and protective mechanisms 15
III. Physiology 17
Maintenance of lens water and cation balance 17
Lens epithelium: site of active transport 17
Pump-leak theory 17
Accommodation 19
IV. Embryology «* 21
Normal development 21
Lens plate 21
Lens pit 21
Lens vesicle 21
Primary lens fibers and the embryonic nucleus 21
Secondary lens fibers 24
Lens sutures and the fetal nucleus 24
Tunica vasculosa lentis 24
Zonules of Zinn 25
Congenital anomalies and abnormalities 26
Congenital aphakia 26
Lenticonus and lentiglobus 26
Lens coloboma 27
Mittendorf's dot 27
Epicapsular star 28
Peters anomaly 28
Microspherophakia 28
Aniridia 30
Congenital and infantile cataract 30
Morphologic classification of congenital and infantile cataracts 32
Developmental defects 37
Ectopia lentis 37
Marfan syndrome 37
Homocystinuria 38
Hyperlysinemia 38
Sulfite oxidase deficiency 39
Ectopia lentis et pupillae 39
Persistent fetal vasculature 39
V. Pathology 40
Aging changes 40
Nuclear cataracts 40
Cortical cataracts 42
Posterior subcapsular cataracts 43
Drug-induced lens changes 49
Corticosteroids -49
Phenothiazines 49
Miotics 49
Amiodarone 50
Trauma 50
Contusion 50
Perforating and penetrating injury 52
Radiation-induced cataracts 52
Chemical injuries 54
Intralenticular foreign bodies 54
Metallosis 54
Electrical injury 55
Metabolic cataract 55
Diabetes mellitus 55
Galactosemia 57
Hypocalcemia (tetanic cataract) 58
Wilson disease (hepatolenticular degeneration) 58
Myotonic dystrophy 58
Nutritional disease 4 . . 59
Cataract associated with uveitis 59
Exfoliation syndrome 60
True exfoliation 60
Exfoliation syndrome (pseudoexfoliation) 60
Cataract and skin diseases 61
Atopic dermatitis 61
Lens-induced uveitis 62
Phacoantigenic uveitis (phacoanaphylactic uveitis) 62
Lens-induced glaucoma 62
Phacolytic glaucoma 62
Lens-particle glaucoma 63
Phacomorphic glaucoma 63
Glaukomflecken 63
Ischemia 64
Cataracts associated with degenerative ocular disorders 64
VI. Epidemiology of Cataracts 66
VII. Evaluation and Management of Cataracts in Adults 69
Clinical history: signs and symptoms 69
Decreased visual acuity 69
Glare 69
Contrast sensitivity 70
Myopic shift 70
Monocular diplopia 70
Medical management 70
Low-vision aids for cataract 71
Indications for surgery 71
Preoperative evaluation 72
General health of the patient 72
Pertinent ocular history 72
Social history 72
Planning postoperative care 73
External examination 73
Motility 73
Pupils 73
Slit-lamp examination 74
Conjunctiva 74
Cornea 74
Anterior chamber 74
Iris 75
Crystalline lens 75
Limitations of slit-lamp examination 75
Fundus evaluation 75
Ophthalmoscopy 75
Optic nerve w 76
Fundus evaluation with opaque media 76
Measurements of visual function 76
Visual acuity testing 76
Brightness acuity 76
Contrast sensitivity 77
Visual field testing 77
Special tests 77
Potential acuity estimation 77
Tests of macular function 78
Preoperative measurements 78
Refraction 79
Biometry 79
Corneal pachymetry 79
Specular microscopy 79
Patient preparation and informed consent 80
Historical development of cataract surgery 81
Couching 81
Early extracapsular extraction procedures 83
Early intracapsular extraction procedures 84
Modern extracapsular'techniques . 84
Anesthesia for cataract surgery 85
Historical considerations 85
General anesthesia 86
Local anesthesia 86
Topical anesthesia 87
Preoperative and intraoperative preparation 89
Theory of wound construction for cataract surgery 90
Single-plane incisions 91
Multiplane (scleral tunnel) incisions 91
Clear corneal incisions 93
Modification of preexisting astigmatism 94
Types of cataract surgery: intracapsular cataract extraction 96
Advantages 96
Disadvantages 96
Indications 97
Contraindications 97
Instrumentation 97
Patient preparation : 98
Procedure 98
Postoperative course 100
Types of cataract surgery: extracapsular cataract extraction
with nucleus expression 100
Indications 100
Contraindications 101
Instrumentation 101
Procedure 102
Postoperative course 104
Types of cataract surgery: phacoemulsification 104
Making the transition 104
Patient selection 105
Instrumentation 105
Procedure 112
Clear lens extraction 137
Pars plana lensectomy 137
Indications 137
Contraindications . 137
Instrumentation 137
Procedure 137
Primary intraocular lens implantation in adults 138
Historical perspective 138
Design considerations 140
Posterior chamber lOLs 142
Multifocal lenses 144
Phakic lOLs 144
IOL power determination 145
Instrumentation 149
Procedure 150
Contraindications 152
Intraocular lens implantation in children 153
Indications 153
Contraindications 154
Procedure 154
Postoperative course 154
Viscoelastics 154
Physical properties 155
Desired properties of viscoelastics 156
Viscoelastic substances 156
Outcomes of cataract surgery 157
X. Complications of Cataract Surgery 160
Shallow or flat anterior chamber 160
Intraoperative 160
Postoperative 1.62
Corneal edema 163
Stromal and epithelial edema 163
Brown-McLean syndrome 163
Vitreocorneal adherence and persistent corneal edema 164
Corneal complications of phacoemulsification 164
Detachment of Descemet's membrane 164
Toxic solutions 164
Hemorrhage 165
Retrobulbar hemorrhage 165
Suprachoroidal hemorrhage or effusion 166
Expulsive choroidal hemorrhage 166
Delayed choroidal hemorrhage 167
Hyphema 167
Retinal light toxicity 167
Elevated intraocular pressure 168
Cystoid macular edema 168
Retinal detachment 170
Endophthalmitis 171
Diagnosis 171
Treatment 172
Chronic uveitis 173
Capsular rupture 173
Corneal melting with ocular surface disease 174
Wound leak or filtering bleb 175
Iridodialysis 175
Cyclodialysis 175
Ciliary block glaucoma (malignant glaucoma) 175
Retained lens material 176
Vitreous disruption or incarceration in wound 177
Induced astigmatism 177
Pupillary capture 178
Epithelial downgrowth 178
Capsular opacification and contraction 179
Posterior capsule opacification 179.
Anterior capsule fibrosis and phimosis 180
Nd:YAG capsulotomy 181
Complications of IOL implantation 184
Decentration and dislocation 184
Uveitis-glaucoma-hyphema (UGH) syndrome 185
Corneal edema and pseudophakic bullous keratopathy 185
Wrong power IOL 186
X. Cataract Surgery in Special Situations 187
Cataract in children '187
Surgical planning 187
Surgical technique 188
Complications 188
Prognosis 188
Correction of aphakia 189
Anticipated poor wound healing 190
Psychosocial considerations 191
Claustrophobia 191
Dementia or other mental disabilities 191
Inability to communicate with the patient 191
Systemic conditions 191
Anticoagulation therapy or bleeding diathesis 191
Arthritis 192
Chronic obstructive pulmonary disease (COPD) 193
Diabetes mellitus 193
Obesity 194
Ocular conditions 195
External eye disease 195
Corneal conditions 196
Developmental abnormalities 199
Increased risk of expulsive hemorrhage 202
Glaucoma 204
High refractive error 210
Hypotony 211
Uveitis 212
Retinal disease 212
Trauma 213
Visualization 214
Inflammation 214
Retained foreign matter 214
Damage to other ocular tissues 214
Zonular dehiscence with lens subluxation or dislocation 215
Lens implantation 216
Basic Texts 217
Related Academy Materials 219
Credit Reporting Form 223
Study Questions 225
Answers 234
Index 239
