Index

Aberration  151, 208, 283–284 Aberration

control  153, 205, 285, 405 controlled lens  405

Aberrometry  31 autorefraction  31 Harkmann-Shack  31 laser ray tracing  31 psychophysical  31

Tscherning aberroscope  31 Absolute contour map  25, 26f Acanthamoeba keratitis  50, 53, 141,

347–348

Accelerated stabilization design (ASD)  266, 266f

Accidents, decontamination  53 Acidosis, stromal  5

Acuity  181–182, 326, 376 Acute red eye  232, 246 Adhesion, lens  184–185, 327 Adrenalin  51

AEL (Axial edge lift) see Edge lift aesthesiometer  405

Aftercare  325–343

additional procedures  359–365 PMMA wearers, refitting  359–362

with gas-permeable lenses    360–361

physiological problems  359 problems with  360 procedures  360–361

fitting  360–361 problems  361

soft lenses  361–364 rigid gas-permeable  363

prescribing spectacles for contact lens wearers  362–364

rigid lens modification  364–365 ageing lenses see Ageing lenses complications  345–357

emergencies and infections see Emergencies and infections

grief cases (drop outs) see Grief cases limbus see Limbus

problems

visual see Visual problems wearing see Wearing problems

visit, first  325–329 clinical adjustments/

changes  328–329 discussion with patient

initial  325–326 further  329

fitting assessment, white light  326 fluorescein fitting assessment, Burton

lamp  327

slit lamp examination, lenses removed    327–328

slit lamp examination, lenses in situ    327

supplementary procedures, lenses in situ  327

supplementary tests, lenses removed    328

visual acuity and over-refraction  326 Ageing lenses  353–356

rigid gas-permeable  356 deposits  356 discoloration  356

surface and edge deterioration  356 soft  353–356

discoloration  355 fitting changes  355 protein film  353

refractive changes  355–356 rust spots  355

surface and edge deterioration  355 white spots  355

AIK (asymptomatic infiltrative keratitis)    347

Air bubbles, trapped see Dimpling Air optix individual lens  228–229

Aqua Multifocal lens  291 fitting method  229 material properties  229

parameters available  226t, 229, 229t related lenses  229

specification, typical  229

Albinism and children  371, 391 Alcian blue  19, 50

Alcohol, polyvinyl  307 Aldox  306

Alignment

curve  176, 179

and high/low riding lens  182–183 and lens behaviour  175–176

fitting  405 Alomide  51 Alternating vision  405

Amblyopic occlusion  371 Amethocaine  50 Ametropia

correction  66 refractive  60

Ammonias, quaternary  307 Anaesthetics

and children  368

and epithelium  50, 349b topical  50

Anatomy  1–4 conjunctiva  2–3 cornea  1–2

Bowman’s membrane  2 corneal sensitivity  2 Descemet’s membrane  2 endothelium  2 epithelium  1

stroma  2 eyelids  3 tear film  3–4

see also Physiology Aniridia  372 Anisometropia  61, 370 Anitimicrobial agents  50

Brolene (0.1% propamidine isethionate)    50

chloramphenicol  50 fucithalmic  50

Anoxia  4, 405

Anterior segment photography  31–33 contrast sensitivity (CS)  33

function (CSF)  33 visual acuity  33

image capture, advantages of   32–33 Apex lens  388

Aphakia  61, 386–389 rigid lenses  387–389

Apex  388

corneal lens fitting  387 corneo-scleral  388–389

Dyna intra-limbal  388–389 soft lenses  389

continuous wear  389 hydrogel  389 silicone hydrogel  389

Apical

alignment fitting  144 clearance  382, 405 lens  379

radius compared with keratometry  24f touch  405

Apoptosis, cell  6 Appendices

Vertex conversion table  397t–399t Dioptic-millimetre conversion

table  397t–399t Applications, and features, special lens see

Special lens applications and features

Aqueous deficiency  87–89 Aquila lens  154

Arcuate staining  225, 227, 231 Artificial tear supplements  87 Artificial tears, low viscosity  87

ASD (Accelerated stabilization design)  266, 266f

Asepticization see Pasteurization Aspheric lenses  207–209

advantages and disadvantages  151, 152f

back surface  207–209 definitions  128–129 designs  152–156

fully aspheric  152–153 Menicon Z-Alpha  153 Quasar  152–153

tear layer profile  153f mainly aspheric/part

asphere  155–156 Astrocon  155–156 MetrO2  156 Quantum  155

mainly aspheric/part sphere    154–155

Aquila  154 Asphericon  154–155

tear layer profile  155f Persecon E  154

fitting

considerations, general  158 fluorescein patterns compared with

spherical lenses  158

spherical cornea  158 toric cornea  158

fully aspheric  156

mainly aspheric/part sphere   

156–157

Aquila  156–157 Persecon E/92E  156

mainly spherical/part asphere  157–158

Astrocon HDS  157–158 Metro2 and maxim ultra  157 Quantum  157

principles  156–158 front surface  208

Soflens daily disposable  208–209 fitting technique  209 geometry  209

parameters available  209, 209t related lenses  209 specification, typical  209, 405

spun-cast  209–210 advantages of   209–210 disadvantages of   209–210 geometry  210, 210f

surface representations  129f tear layer profile  128f

unusual performance  210–211 too loose  210–211

too tight  210–211 Asphericon lens  154–155, 155f Association of British Dispensing

Opticians  40 Astigmatic lens  148 Astigmatism  64

corneal  65, 67–68, 258, 273–274 induced  182, 254, 258, 410 lenticular  269–270, 273

fitting  272

and orthokeratology  181–182 residual  67–68, 253–254, 258, 413 rigid pas-permeable lens fitting  148 toric lenses  254, 263–264, 267

Astrocon lenses  155–158 Asymptomatic infiltrative keratitis (AIK)   

347 Autoclave  405 Autokeratometers  23

see also Keratometers Autorefraction  31

Axial edge lift (AEL) see Edge lift Axial maps  27, 28f

Axial (sagittal) map  27, 28f

Back optic zone diameter (BOZD)  133–135, 176, 406

Back optic zone radius (BOZR)  132, 163, 176, 237, 406

Back peripheral radius (BPR)  406

Back peripheral radius (BPZR)  163

Back surface toric  406 see also design and fitting under Toric soft lenses

Back vertex power (BVP) and overrefraction  137–139, 138f

BAK (Benzalkonium chloride)  306

Band magnifier (measuring magnifier)  164 Bandage lens  193, 227, 231, 390,

394–395, 406 Base curve  406

Bausch & Lomb keratometer  21, 21f, 23b slit scan topography  25 Softlens  208–209

spun-cast lenses  209–210, 210f Benoxinate  50, 89

Benzalkonium chloride (BAK)  306 Bi-aspheric  406

lenses  129, 152, 291, 406 Bicurve  406

Bicurve corneal lens  124–126, 125f tear layer profile  125f

Bifocal lenses see fitting soft and lens designs under Presbyopia

Binding  406 Biocompatability  406

Biocompatible and biomimetic lenses  107 Biomimesis  107, 406

Bitoric lenses  256, 262, 406 avoiding need for  260, 260b fitting  259

Blending  406

Blinking  71 exercises  90–91

wearing problems  341 Blur test  280b Bowman’s membrane  2

BOZD (back optic zone diameter)  133–135, 176, 406

BOZR (back optic zone radius)  132, 163, 176, 237, 406

BPR (Back peripheral radius)  406 Break-up time (BUT/TBUT)  81–82, 406 Brolene (0.1% propamidine isethionate)   

50 Broleze  50–51 Buffer  305–308, 310t

Bulbar conjunctiva  70, 233, 337 fitting  200

assessment  326b, 327 red eye  346–347

Bullous keratopathy  394–395, 406

Burton lamp  34–35, 142–143, 407 fluorescein pattern observation  49, 119,

142, 142f

BUT (tear break-up time)  81–82 BVP (back vertex power) and over-

refraction  137–139, 138f

CAB see Cellulose acetate butyrate

CAEL (Constant edge lift) see under Edge lift Care systems

cleaning solutions see Cleaners compliance and product misuse  318 contact lens case  318

disinfection see Disinfection solutions see Solutions

Carrier (BS)  407

Case hygiene see Disinfection Cast moulding  407

CCLRU (Cornea and Contact Lens Research Unit)  42

Cell apoptosis  6

Cellulose acetate butyrate (CAB)  97–98, 100b, 307

Children and therapeutic lenses  367–373 therapeutic applications  368

additional  395, drug-release  395 bandage lenses  394–395

soft  394

general considerations  394 complex lenses see design under Complex

lens, children instrumentation  369 management  367–368

anaesthetics  368 of child  367 hypnosis  368

insertion and removal  367–368 insertion  367–368

removal  368 parental  367

non-therapeutic fitting  369–370 refractive applications  370–371

albinism  371

amblyopic occlusion  371 aniridia and iris coloboma  372 anisometropia  370

aphakia  371

applications  371–372 hypermetropia  370

limbal diameter RGP lenses  395 Marfan’s syndrome  372 microphthalmos  372

myopia  370 control  370

orthokeratology  370

silicone rubber lenses  393–394 advantages  393–394 disadvantages  394

see also Keratotomy Chloramphenicol  50 Chlorbutol  307

Chlorhexidine digluconate (CHX)  306 CIBA Dailies Aqua Comfort Plus

(CIBAVision) lens  92 Clayrimist  90

Cleaners  101b, 328 periodic  314

solutions  349–350, 349b sorbic acid  307

surfactants  307–308, 311, 313, 316 polyhexanide systems  310t polyquad systems  310t

wetting agents  308 see also Enzyme tablets Cleaning and rejuvenation,

professional  53–54 ‘CLEK’ standardized fitting set  382 Climbing, high altitude  303 Clinical

equivalents  407 grading  42–44

grading scales, published  42–44 CCLRU  42

Efron  43

Institute of Optometry  43–44 CLIPC (lens-induced papillary

conjunctivitis) see under Conjunctiva

Collagen lenses  107

Collection of lens see under Lens collection and patient instruction

College of Optometrists  40 Combination lenses  392–393, 407

multicurve soft scleral  386 ‘Piggy-back’  386, 392

rigid centre with soft periphery  392–393 Softperm  386t, 392–393

SynergEyes  393, 393t

Committee on the Safety of Medicines  41

Comparator  237 Complex lenses

colour vision enhancement  299–300 Chromagen  299–300

X-chrom  299 designs

children  375–396 corneal irregularity  391

rigid gas-permeable lenses  391 soft lenses  391

albinos  391

high myopia and hypermetropia  376 hydrogel lenses  376

rigid gas-permeable lenses  376 silicone hydrogel lenses  376

see also Complex lenses; Presbyopia, lenses for; Special lenses; Toric rigid lenses; Toric soft lenses

Compression moulding  407 Computers and toric rigid lenses  262 Concentric bifocals  284–285, 284f,

288–290 Conditioning

agents  316–317 solution  315–318, 407

Conflex/Conflex Air lens  124 Confocal microscope  33–34 Conjunctiva  2–3, 341

bulbar see Bulbar conjunctiva and children  368 conjunctivitis

giant papillary  74, 338, 409 lens-induced papillary  247, 250, 407

folds, parallel (LIPCOF)  76–77, 85, 85t mucin production  76

ocular examiation  19, 341 palpebral  2–4, 70, 141b–142b, 241,

339, 339b

papillary  20b, 70, 71b, 328, 337–339 scleral  382

staining  42–43, 71, 81 fluorescein  19, 83, 141b–142b

Conjunctival epithelial flaps  233 Conoid lens  123 , 379, 407

Considerations, preliminary see Preliminary considerations

Constant axial edge lift (CAEL) see under Edge lift

Consulting room procedures ancillary items  54

insertion and removal of lenses  54–56 rigid gas-permeable and PMMA  55

insertion  55 removal  55

soft  55–56

insertion  55–56, 56b removal  56, 56b

professional cleaning and rejuvenation  53–54

rigid lenses  53–54 soft lenses  54

solutions and drugs  48–51 topical anaesthetics  50 verification of lenses  54

see also Decontamination; Disinfection; Hygiene; Solutions

Contact angle  10–11, 407 Contact lens-induced papillary

conjunctivitis (CLIPC)  407 Contaminated lenses  351

Continuous wear see Extended wear Contour maps

absolute  26f relative  27f

Contrast sensitivity function (CS)  33 Contrast sensitivity and ‘quality of

vision’  69 Conventional lens  353, 407 Cornea

abrasions  349 anatatomy  1–2 astigmatism  67–68 corneal irregularity  391

soft lenses  391 corneal lens  407 corneal thinning  250 exhaustion  242, 407 grafts see keratoplasy hypoxia  2, 4–5, 16, 250 metabolism  4

moulding  254, 284, 407

sensitivity  6, 62, 359, 361, 377, 388 temperature  5

topographer see Topography warpage  29–30, 360

see also under Anatomy, Wearing problems

Cornea and Contact Lens Research Unit (CCLRU)  42

Corneo-scleral (mini-scleral) lens  382–384, 388–389, 411

Cosmetic and prosthetic lenses  296–300 Cosmetic wear  61–62

Crossed monovision  280b

CRT (corneal refractive therapy) see Orthokeratology

CS (Contrast sensitivity function)  33 Custom made lenses  228–229 , 271 Cyclosporine  91

Data Protection Act  44 Decontamination

accidents  53

rigid gas-permeable and PMMA lenses    52–53

soft lenses  53

trial lenses  47, 51–53 Dellen (Fuch’s dimple)  337 Descemet’s membrane  2 Diabetes  62, 244 Diagnostic lens  51, 408 Dimpling  300, 408

and aftercare  181, 335–336 Dellen (Fuch’s dimple)  337

hydrogel/hydrogel silicone lenses  231, 246, 248

and keratoconus  376–377 rigid gas-permeable lenses  118,

180–181, 185 Disinfection  309–315, 408

case hygiene  314 chemical  309–315

multipurpose solutions  309–310 chlorine systems  312 hydrogen peroxide  310 polyhexanide systems  310t polyquad systems  310t

heat  312–313 microwave  312 saline  312, 312b

standards  308–309

ISO/FDIS 14729 performance requirements  308t

regimen test  309 Stand alone test  309

trial lenses  47

see also Enzyme tablets Disposable lenses  213–224, 408

advantages  214–215 aftercare  217–222

solutions, multipurpose  222 handling  217–222

as trial lenses  223–224 , 271–273, 342 disadvantages  215

fitting  217

frequent replacement  213–214

other uses for  223–224 practice management  222–223 types of   215–217, 216t

Silicone hydrogels see disposables under Silicone hydrogel

daily disposables  215–217, 218t monthly and two weekly  215–217,

216t

multifocal and bifocal  217, 221t toric  217, 219t–220t

Diving  303

Dk

and Dk/t (Fatt) and ISO units compared  7t

values compared to oxygen flux  9t see also permeability under Oxygen

Dominance, eye  279–280 ’Donut’ stain  335f

Dot matrix soft lens  306

Drop-outs (grief cases) see Grief cases Drops for eyes  310t, 317

Drugs  48–51 adrenalin  51 Lodoxamide  51

sodium bicarbonate  51 sodium cromoglycate  50–51 solutions and  48–51

systemic, side effects  353, 354t Dry Eyes  76–78

aqueous deficiency  76 contact lens signs  86–87

hydrogel lenses  86–87 rigid gas-permeable  86–87

Lacrytest  86

lens management  92–93 materials  92

hydrogel lenses may improve tolerance  91

lenses with internal wetting agent  91

rigid gas-permeable  92

thin low water content lenses  91 lid parallel conjunctival folds  84, 85t lipid deficiency  77

marginal  77–78 mucin content  76

ocular surface conditions  77 osmolarity measurement  85 protein assays  86

tear dilution test  86 tear ferning test  86 treatment  87–91

aqueous deficiency  87–89 artificial tear supplements  87

delivery of   90 artificial tears

high viscosity  88 low viscosity  87

Clayrimist  90 conjunctival folds  91 diet  91

EyeBag  89–90

lipid deficiency  89–91 mucin production  91 punctal plug  88–89 tear retention  88 therapeutic  91

cyclosporine  91 viscoelastics (thixotropic)  88

upper Lid Margin Staining  85 see also Tear film

Drysdale’s method of soft lens verification  238

Durasoft 3 lite tint lens see under Semiscleral lenses

Eccentricity  29, 31, 128, 140, 408 aspsheric  128, 151–152, 156, 158 orthokeratology and reverse

geometry  170, 172, 380, 388 rigid gas-permeable  158, 176, 179–180

Edge lift

axial (AEL)  116, 117f, 405

constant (CAEL)  116–117, 117t, 126, 282, 407

radial (REL)  117, 117f, 413 Efron grading scale  43 Elasticity of soft lenses  204

Elastomers (silicone rubber lenses)    107–108, 250

Elderly patients, suitability of   63 Elliptical ‘K’ (Persecon keratoconus)

lens  380

Emergencies and infections  345–351 broken/displaced lenses  350 causes of   351

contaminated lenses  351 corneal abrasions  349 courses of action  351–352 foreign bodies  349

grief cases (drop-outs)  351–352 avoiding  352

infections and inflammatory responses  345–348

contact lens acute red eye (CLARE)/ acute red eye

reaction  346–347 contact lens peripheral ulcer

(CLPU)  346 keratitis see Keratitis

lens ageing see Ageing lenses overwear syndrome (acute epithelial

necrosis/3 am syndrome)  348–349

solutions, problems with  349–350 systemic drugs, side effects of   353, 354t

Enhanced monovision  292 Endothelium  2, 4–5

endothelial polymegathism  250 , 341, 359, 412

lens complications grading scales  43 slit lamp observation  18, 19f specular microscope  33

Enzyme tablets  314 deposit removal  356 liquid  314, 317

non-disposable lens disinfectation  338 rigid gas-permeable lenses  317 solution problems  349–350

use of   310, 342

EOP (equivalent oxygen percentage)  8, 9f Epithelium  1

and anaesthetics  50, 349b anatomy  1–2, 1b, 76 damage to  349, 394

and diabetes  62, 244 keratomileusis, laser assisted

(LASEK)  410 and lens complications  43 microcysts  247–248 necrosis, acute (overwear

syndrome)  348–349 and orthokeratology  170

and oxygen  1, 4, 8–9, 250

and staining  19, 49–50, 53, 334–335 thinning  250

tissue fragility  5 Etafilcon A IV 1  97

European Standard materials classification (BS EN ISO 11539: 1999)  95

Examination techniques  142–143 Preliminary see Preliminary

considerations Expiry date  408 Extended wear  407–408

advantages of   245

rigid lenses  245 soft lenses  245 approaches to  243 continuous  243

flexible (daily plus)  243 up to 1 month  243

children using  392, 394 fitting

rigid gas-permeable lens  249 soft lens  245–246

long-term consequences of   250–251 corneal thinning  250

endothelial polymegathism  250 infection and inflammatory

response  250 metabolic activity  250 neovascularization  251 vascularization  250–251

other lenses  250 silicon elastomer  250

patient selection  244–245

indications and contraindications  244 physiological requirements  241–243

oxygen  241–242 effects of lack of   242

physical and chemical compatibility of materials  243

tears exchange and osmolarity  242–243

rigid gas-permeable lens problems  249–250

3 and 9 o’clock staining  249 breakage and loss  248–249 deposits  248

epithelial microcysts  248 infections  247, 249

inflammatory response and corneal infiltrates  247

lens adhesion (binding)  250 lens dehydration and corneal desiccation  246

lens-induced acute red eye  246 lens-induced papillary

conjunctivitis  247, 249 mucin balls  248

oedema  247, 249 vascularization  249

silicone hydrogel aftercare  232–233, 233b

soft lens vascularization  248 Eye

dominance  279–280

drops  310t, 317 dry see Dry eyes

examination, external see under Preliminary considerations

EyeBag  89–90 Eyelids  3, 264, 328

closed conditions during sleep  6 conjunctival folds, parallel  76–77, 85t lid-attachment  410

upper, margin staining  85

FDA see Food and Drugs Administration Features and applications, special lens see

Special lens applications Fenestrated lens for optic measurement

(FLOM)  408 Fenestration  300, 408 Flare  60, 64, 69, 408

hydrogel  376

rigid gas-permeable  91, 121, 133, 171 soft  331, 386

Flexible wear  73, 243, 408 Flexure  98–99, 408

and lens power  194, 200, 204–205, 205b

rigid gas-permeable  148, 158, 331 toric  132–133, 255

FLOM (fenestrated lens for optic measurement)  408 Fluorescein patterns  141–150

Burton lamp  142–143 examination techniques  142–143

white light assessment  144 fitting  141–150

correct  144–145 alignment  144, 144f apically clear  145 flat  145–146

correction of   146 tear layer profile  145f

flatter than ‘K’  145

fluorescein assessment  144–145 steep  146–148

correction of   147 tear layer profile  147f

fluorescein use  141–142 instillation  141–142 ultraviolet inhibitors  142

Slit lamp  143

spherical/part asphere lenses  158 Fluorescein (sodium fluorescein

C20H10O5Na2)  48–49, 409

Fluorexon  49

Fluorosilicon acrylate  99–100, 409 materials  100t

Focimeter  164

Food and Drugs Administration (FDA)  41, 91, 313, 409

Foreign bodies  335, 335f, 349, 409 Fourier analysis  30

Frequent replacement  54, 213–214, 228, 247, 356b, 409

Front optic zone diameter (FOZD)  113– 114, 387

Front surface toric  409 Fuch’s dimple (Dellen)  337 Fucilthalmic  50

Gas-permeable lenses see Rigid gas-permeable

General Optical Council  39–40 Ghost vessels  232, 336, 409

Giant papillary conjunctivitis (GPC)  74, 338, 409

Grading scales see grading scales under Clinical

Grief cases (drop-outs)  351–352 avoiding  352

causes  351

Harkmann-Shack aberrometry  31 Hydration  409

Hydrogel  409

Hydrogel lenses, water content, clinical implications  102–103

high, advantages/disadvantages    103

low, advantages/disadvantages    102–103

Hydrogel and silicone hydrogel corneal diameter lenses  189–193

contraindications  189 fitting  189–192

appearance  190–191, 191f power  190

radius  189–190 total diameter  190 indications  189–192

Lunelle ES 70  192–193 fitting technique  192–193 lens geometry  192 material properties  192 parameters  192 , 192t typical specification  193

disposable lenses see Disposable lenses extended wear see Extended wear fitting

characteristics of correct  199

loose  200–202, 200f tight  200 summarized  201t, 202

considerations  187

aspheric lenses see Aspheric lenses design factors  188–189 dynamic assessment  188

‘push-up’ test  188

high minus (>−6.00 D) and medium to high plus (>+3.00 D)  203

lens flexibility and modulus of elasticity  204

lens power  203–204

low minus (<−2.00 D)  203–204 medium minus (−2.00 D to −6.00 D)

and low plus (<+3.00 D)  204 sagittal height and corneal

measurement  187

large corneas with steep radii  187 small corneas with flat radii  187

thin lenses  206–207 Zero 6 see Zero 6 lens

unusual lens performance visual  204–205

astigmatism  205 environmental factors  205 flexure and liquid lens

power  204–205

wavefront technology and ocular aberrations  205

semi-scleral lenses see Semi-scleral lenses soft lens, fitting and design  187–198 specification and verification  235–239

International Standards and tolerances  235

soft lens specification  235

material property tolerances  236t recommended tolerances  236t

soft lens verification  235–239 back optic zone radius  237

base curve comparator  237 keratometer  237 spherometers  237

wet cell instruments  237 deposits  239

edge form  238 power  237–238

air measurement  237–238 wet cell measurement  238

surface quality  238–239 thickness  238

Drysdale’s method  238 projection magnifiers  238

total diameter  237 comparators  237 power  237–238

projection magnifiers  237 water content and material  239

Hydrogen peroxide  53

Hydron Zero 6 and Z Plus lenses  206, 207t Hydrophilic  409

conditioning agents  316

lenses for children  385–386, 388 rigid gas-permeable lenses  100–101 silicone hydrogel lens  106

soft lens dehydration  105 Hydrophobic  409

Hygiene  47–48

disinfection of instruments, lenses and lens cases  47–48

hand washing between patients  47–48 solutions and drugs  48–51

see also Cleaners; Disinfection; Solutions; Staining agents

Hypercapnia  4–5, 250, 409 Hypermetropia  370 Hypnosis  368

Hypoxia  409

corneal  2, 4–6, 242, 250–251 lens-induced  250

Identification, complex lens  295–296 rigid gas-permeable  305–308

soft  295–296 Impression lens  409 In vitro  410

In vivo  410 Incidence  410

Induced astigmatism induced  182, 254, 258, 410

Infections  247, 249 avoiding  47–48

breakage and loss  248–249 deposits  248

epithelial microcysts  248

and inflammatory response  250 and corneal infiltrates  247

lens-induced papillary conjunctivitis  247, 249

mucin balls  248 neovascularization  251 oedema  247, 249

3 and 9 o’clock staining  249 vascularization  248–251 see also Emergencies

Infiltrates  410

cornea and limbus  70, 246–247

Acanthamoeba keratitis  141, 347–348 and red eye  346–347

stromal  346

Infiltrative keratitis (IK)  347–348 Inflammation  250

see also under Emergencies and infections; Infections

Institute of Optometry grading scale  43–44 Instrumentation  15–35

Burton lamp  34–35 and children  369

controls and focus  15–16 pachymeter  34

Placido disc  34 slit lamp  15–20

confocal microscope  33–34 focusing  16, 16f illumination methods  16–17

direct  16–17, 18f indirect  17, 17f retro-illumination  19f

routine recommended  17–20 specular reflection  19f

specular microscope  33–34 specialist  33–34 thermography  35

see also Anterior segment photography; Keratometers and autokeratometers; Topographers

Intermediate vision  69 International standard classification,

contact lens materials  95 cellulose acetate butyrate (CAB)  97–98 fluorosilicon acrylates  99–100, 100t hydrophilic rigid gas-permeable

lenses  100–101

ionic and non-ionic polymers  102 Polymethyl methacrylate  101 rigid gas-permeable lenses  97–101 rigid gas-permeable material

Paragon HDS  95–97 Paflufocon B III 3  95–97

rigid lenses  161–162

silicon acrylates (siloxanes)  98–99, 98t soft lens

Acuvue 2  97, 101–105 advantages  104

dehydration characteristics  104–105 disadvantages  104

Etafilcon A IV 1  97

thickness, clinical implications of   104 Iris coloboma  372

ISO/FDIS 14729 performance requirements for solutions  308t

Isotonic solution  312, 410

Javal–Schiötz keratometer  21 mires  21f

Keratitis

Acanthamoebic  50, 53, 347–348 infiltrative  347

microbial (suppurative)  345–346 viral  348

Keratoconus  376–386 rigid gas-permeable lenses

‘CLEK’ standardized fitting set  382 designs

acuity  380–381 apical clearance  379 aspheric periphery  380

corneo-scleral  382–384 Elliptical ‘K’ (Persecon

keratoconus)  380

offset and aspheric lenses  379–380 profile design  382

Quasar K  380 Rose K  381 Rose K2  381

So2Clear  382–383 spherical

corneal periphery, to fit  379 to give three-point touch   

378–379

to give two-point touch  377–378 fitting  383–384

central  383 peripheral curve  383

fluorescein instillation  384 insertion  383

ordering  384–385 removal  383

silicone hydrogel lenses  376 total diameter  383

soft lenses  385–386 conical  385 hybrid  385–386

piggy-back systems  386 scleral  386

SoftPerm  386, 386t spherical  385 Synergeyes KC  386

Keratometers and autokeratometers  20–23 Autokeratometers  23

corneal topographers  23–31

analysis (oculus keratograph)  25–31 maps see Maps

topographical shapes  28 apical radius compared with

keratometry  24f Placido based  24–25 Scheimpflug based  25 slit scan  25

keratometer (ophthalmometer) types  20–21

extending the range  23 fixed doubling  21

Javal–Schiötz mires  21f focusing  22 measurement taking  22 topographical  23 variable doubling  21

Bausch & Lomb mires  21f rigid lens verification  163

soft lens verification  237 Keratomileusis, laser assisted epithelial

(LASEK)  410 Keratopathy, bullous  394–395, 406 keratoplasty  390

rigid lenses  390–391 reverse geometry  390

Rose K post graft keratoconus  390 soft lenses  390

Keratotomy, radial and photo-refractive  391–392

rigid lenses  392 soft lenses  392

Lacrytest  86 Lactoplate test  85

LARS mnemonic  268, 270f

LASEK (Keratomileusis, laser assisted epithelial)  410

Laser ray tracing  31 LASIK (laser assisted in situ

keratomileusis)  410

Lateral decentration  183, 183f Legislation see Data Protection Act Lens, ageing see Ageing lenses

Lens collection and patient instruction    319–324

advice, general  322–324 initial  322–324

collection  319 assessment

fitting  319 vision  319

insertion of lenses  319 insertion and removal  319–321

rigid  320 soft  320–321

insertion  320–321 removal  321

lens care  323 precautions  323–324 unusual symptoms  323 wearing schedules  322

Lens specification and replication  39–40 types

advantages of hydrogel  63–64

rigid gas-permeable  65 silicone hydrogel  64

disadvantages of hydrogel  64

rigid gas-permeable  65 silicone hydrogel  64–65

patient’s suitability for

rigid gas-permeable  73–74 new patients  73–74 refits/previous failures  74

soft  72–73

new patients  72–73 refits/previous failures  73

polymethyl methacrylate (PMMA)    65

verification  54

Lens types see in particular Aspheric; Complex; Disposable; Ageing lenses; Rigid; Silicone hydrogels; Soft; Toric

Lid parallel conjunctival folds (LIPCOF)  85, 85t

Lids see Eyelids Limbus  332, 336–337

staining  333, 336–337

LIPCOF (Lid parallel conjunctival folds)  85, 85t

Lipid deficiency  77

deposits  65, 233, 313–314, 356 keratopathy  251

layer  3

tear content  3 tear film

analysis  82–83, 84t dehydration  71 and dry eyes  78, 81

plug see Mucin ball

Lissamine green see under Staining agents Lodoxamide  51

Long-term wear see Extended wear

Management see Aftercare; Care systems; under Children and therapeutic lenses; Collection and patient instruction; Consulting room; Grief cases

Manufacture  12–13 regulation  12 rigid lenses  12

polishing  12 soft lenses  12–13 toric lenses  13

rigid gas-permeable lenses  13 soft  13

Maps

axial  27, 28f contour  25

absolute  26, 26f relative  26, 27f

difference maps  29–30, 182f–184f elevation  29

power profile  164–165 sagittal see axial above tangential  27–28, 28f

Marfan’s syndrome  372 Materials, physical properties  6–11

international classification see International standard classification

oxygen

equivalent percentage  8 oxygen flux  8–9

compared with differences in critical Dk values  9t

percentage profile  9f permeability  6–7

Dk and Dk/t for traditional (Fatt) and ISO units  7t

transmissibility  7 boundary effect  8 edge effect  8 surface effects  7–8

water

content and uptake  10, 102 balance ratio  10, 10t wettability  10–11, 11f, 11t

sessile drop method  11f

Measuring magnifier (band magnifier)  164 Medennium smart plug  89

Medical Device Directive  41–42, 410 Medicines, Committee on the Safety of   41 Meibomian gland  3, 20, 83

disease  76

dysfunction  3b, 63, 78, 410 treatment of   89

patency of   70, 83 Menicon Z-Alpha lens  153 MetrO2 lenses  156–157 Microbial keratitis  232 Microcysts  314, 410

epithelial  247–248 extended wear  232

and oedema  249–250, 328 Micron  410 Microphthalmos  372 Microscopes

confocal  33–34

specular microscope  33–34 Microwave disinfection  312

Mini-scleral (corneo-scleral) lens  382–384, 388–389, 411

Mire images  22

Bausch & Lomb  19f, 21f circular  23, 23b

and fitting  199

and fixed doubling  21 Javal-Schiötz  21f keratometer  200, 201t, 202 separations  20–21, 21b superimposed  22, 22f variable doubling  21

Zeiss  22f

Monocular patients  69, 69b Monovision  279–280, 279b, 291, 411

advantages/disadvantages  278–279 crossed  280b

enhanced  280b fitting for  279–280

eye dominance  279–280 inadvertant wearers  278

partial  280 success rate  293

Mountaineering  303 Mucin

abnormality  78

balls  107, 231, 248, 336, 411 confused with dry spots  230 content  76

deficiency  50, 76 production  91 and tear film  75

wearing problems  336 Multicurve  411

lens  126, 127f Multipurpose solution  411 Myopia  70

control  370

high myopia and hypermetropia  367

Near vision  68–69

Neovascularization  43, 70, 248, 251, 341, 411

Neutralization  411

NIBUT (non-invasive tear break-up time)  81

Nissel aspheric lens  124

Non-invasive tear break-up time (NIBUT)    81, 411

Occupational wear  61–62 Ocular refraction  66, 254

Oculus keratograph see analysis under Topography

Oedema  247

wearing problems  332

Omniflex lens see under Semi-scleral lenses One-piece hard bifocals  286–287, 286t ophthalmometer see Keratometers and

autokeratometers Optic zone diameter  411

Opticians, Association of Dispensing  40 Opticrom  50–51

Optometrists, College of   40 Orthokeratology  169–186, 411

current approach  170–172 advantages of   171–172 disadvantages of   171

historical  169–170

reverse geometry lenses  172–178, 172f clinical appearance  178–179

fluorescein pattern  178, 179f fitting  178–179

empirical  177–178 routine  180–185 aftercare  181

difference map, bull’s eye topographical plot  182f

subsequent  185 overnight wear  180–181 problem solving  181–185

acuity, poor  181–182 central corneal staining  185 central islands  184 dimpling  197

high riding lens  182 lateral decentration  183 ,  

183f

lens adhesion  184–185 low riding lens  183 retainer lenses  185 smiley faces  184

under (slow) reponders  182 fitting four and five curve  175–177

alignment curve  176 periphery  176

total diameter  176 BOZD  176

BOZR  176 power  176

fitting three curve  172–175 BOZD  174

peripheral curve  174

second curve (tear reservoir)  174 specification  174–175

total diameter  174 four curve  173f

topography mapping, corneal  179–180 Osmolarity, tear  5, 78, 87

exchange  242–243 hypnotic shift in  6 measurement  85 Out-of-hours cover  40

Overnight vision correction (OVC)  169 Overnight wear  180–181 Over-refraction  411

aftercare  181, 330

and back vertex power  137–139, 138b spurious  355–356

toric lenses  260–261, 268, 272–274 and visual acuity  326

Overseas prescriptions  301 Overwear syndrome  348–349, 411 Oxygen

consumption  4

corneal requirements  241–242 and epithelium  4, 8–9 insufficient  242

permeability (Dk)  6–7, 7t, 412 fluorosilicon acrylates  99 hydrophillic RPGs  101

silicone hydrogels  105, 227, 232, 314 physical properties see under Materials transmisability (Dk/t)  412

Pachymeter (pachometer)  34, 412 Paflufocon B III 3  95–97

material classification  96t oxygen permeability  96t

Palebral conjunctiva see under Conjunctiva Papillary conjunctivitis see under

Conjunctiva Partial monovision  280 Pasteurization  312, 412 Patient

access to records  39

dry eyes questionnaire  72 elderly, suitability of   63

instruction see under Lens collection and patient instruction

see also Children and therapeutic lenses Peripheral curves see under Rigid lens

selection and fitting Peripheral radius (BPZR)  163 Permeability see under Oxygen Persecon

E lens  154

Elliptical ’K’ (keratoconus) lens  380 Perspex see Polymethyl methacrylate Phenol red thread test  80 Phenylmercuric nitrate  307 Photography see Anterior segment

photography Photo-refractive keratectomy (PRK)   

391–392, 412 Physiology  4–6

cell apoptosis  6

closed eyelid conditions during sleep  6 corneal

metabolism  4 sensitivity  6 temperature  5

oxygen consumption  4 stromal acidosis  5 tear osmolarity  5 tissue fragility  5

‘Piggy-back’combination lens  386, 392

Pinguecula  97, 337, 341 Placido

based topography  24–25

disc  25, 34, 82–83, 201t, 327, 412 PLTF (Pre-lens tear film)  78, 83 PMMA (polymethyl methacrylate) see

Polymethyl methacrylate Polishing  12, 316, 316b

medium/tape  364 modification  364–365 see also Repolishing

Polyhexanide  306, 310t, 312, 316–317 Polymegathism see under Endothelium Polymers, ionic and non-ionic  237 Polymethyl methacrylate (PMMA)  101,

412

lens first designed  123 Polyquats  305–306 Polyvinyl alcohol  307 Potassium chloride  307 Power, lens  237–238

flexure and  194, 200, 204–205 Power profile mapping  164–165 Preformed lens  412

Pre-lens tear film (PLTF)  78, 83 Preliminary considerations and examination  59–74

contact lenses or spectacles?  60–63 advantages  60 contraindications  61–62 disadvantages  60

indications  61 see also lens types

discussion  59

eye examination, external  69–72 bulbar conjunctiva  70

cornea and limbus  70 lids  70

near vision  68–69

visual considerations  66–69 ametropia correction  66, 67f astigmatism, corneal and

residual  67–68

Spherical cornea with astigmatic refraction  68

spherical cornea with spherical refraction  68

toric cornea with astigmatic refraction  68

toric cornea with spherical refraction  68

blinking  71

contrast sensitivity and ‘quality of vision’  69

intermediate vision  69 monocular patients  69 ocular refraction  66 patient

questionnaire on dry eyes  72 suitability for lens types  72–74

Pre-ocular tear film (POTF)  80, 83 Presbylite lens  287, 287f Presbyopia

fitting rigid multifocals and bifocals  282–288

alternating types  285–288 concentric bifocals  288 one-piece hard bifocal  286–287,

286t, 287f Presbylite  287

solid segmented bifocals  285–286, 286f

simultaneous types  282–285 aspheric  282

back surface  282–283 back surface  282–283 back surface  285

concentric bifocals  284–285, 284f

front surface  285 high eccentricity

designs  282–283

low eccentricity designs  283 material implications  284 multifocal  284

rigid gas-permeable diffractive bifocals  285

S-form technology  283–284 simultaneous types  282–285

fitting soft bifocals  282–288 alternating types  291–293, 292f

enhanced monovision  292 simultaneous types  288–291 aspheric bifocals  290–291

back surface aspheric  290 front surface aspheric  290–291 mulit-aspheric  291

concentric bifocals (spherical)  288–290

centre distance  289–290, 290f centre near  289

lens designs for  280–282 alternating designs (translating

bifocals)  281–282, 281f

alternating designs (translating bifocals)  281–282, successful fitting, factors for  281–282, 282f

simultaneous (non-translating bifocalsor

multifocals)  280–281 successful fitting, factors for  280 centre distance lenses  281

centre near lenses  281 monovision  278–280

advantages  278–279 disadvantages  279 fitting for  279–280

eye dominance  279–280 partial  280

patient selection  277–278 existing lens wearers  278

contraindications  278 indications  278

new  277–278 contraindications  277–278 indications  277

Prescriptions  233 overseas  301 Preservatives  412

Aldox  306

benzalkonium chloride (BAK)  306 Chlorbutol  307

chlorhexidine digluconate  306 phenylmercuric nitrate  307 polyquats  305–306 quaternary ammonias  307 sorbic acid  307

Thiomersal  306 water-soluble cationics  306

Prevalence (of a disease)  412 Prism ballast  413

opaque painted/printed  299 rigid  113, 166

bi/multifocal alternating  287–288, 287b

stabilization  264–267, 269–270 toric soft  13, 209, 219t

PRK (photo-refractive keratectomy)  391– 392, rigid lenses  392

Problems see Visual problems; Wearing problems

Procedures see additional under Aftercare; Care systems; Consulting room; Hygiene

Profile matching  413

Projection magnifier  164, 237–238 Propamidine isethionate (Brolene)  50 Prosthetic tinted lenses  296–300, 297f Protein

assays  86

deposits/film  331–333, 338, 356 and disinfection  51

mucin  50

removal  307–308, 311–317 tear  2–3, 86, 102

Pseudomonas aeruginosa  141b–142b, 345–346, 347b

Psychophysical aberrometry  31 Ptosis  339

Punctal plug  88–89

Quantum lenses  155, 157–158 Quasar lens  152–153, 153f, 380 Quaternary ammonias  307

Questionnaire on dry eyes, patient’s  72, 79

Radial edge lift (REL) see under Edge lift Radial keratotomy (RK)  382, 391–392,

413 Radiuscope  163, 165, 413

Drysdale’s method  238 Record keeping  37–45

clinical grading  42–44 complaints  39

legal implications  37–42 Data Protection Act  44 informed consent  37–42

Medical Device Directive  41–42 out-of-hours cover  40

product liability  41 record cards  42

computerization and Data Protection Act  44

patients access to  39 responsibilities to patients  40 specification and replication  39–40 telephone conversations  39

yellow card reports  41 Refraction see Over-refraction Regimen test  309

REL (Radial edge lift) see under Edge lift Relative contour map  25, 27f Repolishing  53–54, 330, 338, 364 see also

Polishing

Residual astigmatism see under Astigmatism Reverse geometry lenses  129, 413 see also under Orthokeratology

Reversible corneal therapy (RcT) see Orthokeratology

Rigid gas-permeable lenses (RGPs)  413 Rigid lens design  111–122

development  123–130 current

aspheric see Aspheric lenses bicurve, tricurve and

multicurve  124–126,   125f

constant axial edge lift  126 multicurve  126, 127f reverse geometry lenses  129 tricurve  126, 126f–127f

early  123–124 aspheric  124

Conflex/Conflex Air  124 Nissel  124

principles, forces controlling  111–116 capillary attraction  113

centre of gravity  111–112, 112f edge clearance concept  118–119 edge lift concept  116–119

axial (AEL) and radial (REL)  117f CAEL values, average  117t

edge shape  115–116, 116f frictional forces  112 interpalpebral lenses  121

advantages  121 disadvantages  121

lid attachment lenses  120–121 advantages  120–121 disadvantages  121

peripheral curve contributions band width method  118 step-by-step method  118

specific gravity  113, 113t tear layer thickness  119, 119f

thickness and lenticulation  113–114, 114f–115f, 114t

refractive index of materials  115 Rigid lens selection and fitting  131–140

astigmatic  148

back optic zone diameter (BOZD)  133–135

back optic zone radius (BOZR)  132 back vertex power (BVP) and overrefraction  137–139, 138f fluorescein patterns see Fluorescein

patterns peripheral  148–149

lens position  150t

loose  148–149 tight  148–149 peripheral curves  135

tear layer profile/BOZD  134f average periphery  136f loose periphery  137f tight periphery  136f

satisfactory  131–132 topographers, lens design by

corneal  139–140 total diameter (TD)  133

Rigid lens specification and verification  161–167

back and front vertex power (BVP and FVP)  164–165

centre and edge thickness (tc and te)  165

thickness gauge  165 Rigid lens specification and

verification  161–167

designs individual  162 proprietary  162

International Standards  161–162 terms  161–162

types and fittings  162 tolerances  166, 166t verification  162–166

back and front vertex power (BVP and FVP)  164–165

centre and edge thickness (tc and te)  165

edge form  165 focimeter  164

power profile mapping  164–165 radiuscope  165

back optic zone radius (BOZR)  163 Keratometer  163

radiuscope  163 toposcope  163

material  165

peripheral radius (BPZR)  163 surface quality  165

total diameter and zone diameters  164 measuring magnifier  164 projection magnifier  164

V gauge  164

Rinsing see under Saline solution

RK (Radial keratotomy)  382, 391–392, 413

Rose bengal see under Staining agents Rose K lenses  381

Safety of Medicines, Committee on  41 Sagital (axial) map  27, 28f

Sailing and aquatic sports  302–303 Saline solution  48, 48b, 237, 323,  

383

and buffers  305, 311 disinfection  53, 312, 312b eye wash  49, 53

power profile mapping  164–165

rinses and solutions  49, 214–215, 309, 312, 314, 318, 328, 335–336, 389

and solution problems  350b

and staining agents  71–72, 83–85, 141–142, 141b–142b

Schirmer test  80–81 Scleral conjunctiva  382 Scleral lens  413

SEAC (Spongiform Encephalopathy Advisory Committee)  51

Semi-scleral lenses  193–198, 413 contraindications  193 examples

Durasoft 3 lite tint  196–197 fitting method  197

lens geometry  197 material properties  196

parameters available  197, 197t related lenses  197 specification, typical  197

Omniflex  197–198 fitting method  197 material properties  197

parameters available  197,   198t

related lenses  198 fitting  193–196

appearance and lens movement  194, 195f–196f

clinical equivalents  195

loose fitting improvement  196 power  194

radius  193–194

tight fitting improvement  196 total diameter  194

indications  193–196 SF (shape factor)  29 Shooting, competition  303

Silicon acrylates (siloxanes)  98–99, 98t, 413

Silicone hydrogel lenses  105–107 advantages  106–107

aftercare  230–233 arcuate staining  231 dryness  231

mucin balls  231

papillary conjunctivitis  231 complex  229

custom made  228–229 disadvantages  106–107 dispensing  230

handling  230

lens disinfection  230 wearing schedule  230

as disposables

custom made  228–229, Air optix individual see Air optix individual lens

daily

advantages  227 disadvantages  227

fitting  227–228 power  228 radius  227–228 total diameter  228

monthly and fortnightly  226t extended wear  232–233

acute red eye  232

conjunctival epithelial flaps  233 deposits  233

microbial keratitis  232 microcysts  232

papillary conjunctivitis  232 prescription  233 vascularization  232

see also Emergencies and infections Silicone lenses  107–108

advantages of   108 disadvantages of   108

rubber lenses (elastomers)  107–108, 250

see also Silicone hydrogel lenses Siloxane (silicon acrylate)  98–99, 98t,  

413

Simultaneous vision  363, 414 CN lenses  291

Skiing  303

Slit lamp see under Instrumentation Smiley faces  184

Soaking solution  414 Sodium bicarbonate  51 Sodium cromoglycate  50–51 Sodium hypochlorite  53b Soflens  208–210, 209t, 210f

Soft lenses see in particular Toric soft and under Hydrogel and silicone hydrogels

SoftPerm lens  386, 386t, 392–393 Solutions  48–51

anitimicrobial see Anitimicrobial agents buffers  305–308, 310t

cleaning see Cleaners

performance requirements for, ISO,FDIS saline (0.9% sodium chloride BP)  48 soaking  414

staining agents see Staining agents topical anaesthetics  50

amethocaine  50 Benoxinate  50

water  48 sterile  48 tap  48

wetting see Wetting agents Sorbic acid  307

Special lens features and applications  295–303

cosmetic and prosthetic  296–300 fenestration  300

problems with  300 uses of   300

identification  295–296 rigid gas-permeable  295 soft  295–296

overseas prescriptions  301 specific applications  302–303

sport  301–303 advantages  301

climbing, high altitude  303 disadvantages  301

diving  303

shooting, competition  303 skiing  303

swimming  302–303 types  302

rigid gas-permeable  302 scleral  302

soft  302 stability  302

tinted  296–300 dot matrix  299 enhanced colour

discrimination  299–300 Chromagen  299–300 X-chrom  299

opaque painted and printed  299 PMMA  297

rigid gas-permeable  296 soft  297–299, 297f

UV inhibitors  299

Spectacle blur  300, 329, 332, 414 Specular microscope  33–34 Spherometer  237

Spin casting  414

Spongiform Encephalopathy Advisory Committee (SEAC)  51

Sport  61 advantages/disadvantages  301 specific applications  302–303 stability

rigid gas-permeable lenses  302 scleral lenses  302

soft lenses  302

see also under Special lemses Spun-cast lenses  209–210

advantages  209–210 disadvantages  209–210 geometry  210, 210f

unusual performance  210–211 too loose  210–211

too tight  210–211 Stabilization  414

see also under Prism ballast; Toric soft Staining

arcuate  225, 227, 231, 414 wearing problems see under Wearing

problems Staining agents  48–50

alcian blue  50

fluorescein, high molecular weight  49 fluorescein sodium BP  48–49, 71,

83–84

lissamine green  49–50, 71–72, 84, 410 rose bengal  49, 71, 84–85, 413

Stand alone test  309 Sterilization  414

Striae  328, 332, 341, 354t, 414 Stroma  346

neovascularization  248, 251 oedema  242, 247, 332, 359 and oxygen  2

stromal acidosis  5 tear osmolarity  5 thinning  250

Suppurative keratitis  345–346 Surfactant  307–308, 311, 313, 414

polyhexanide systems  310t polyquad systems  310t

Swimming and diving  302–303

by calculation  257–259 spherical fitting set  257 toric fitting set  256–257

bitorics  259 compromise back surface

torics  259–260 computers in  262

front surface torics  260–261 method 1:  260–261 method 2:  261

toric peripheries  261–262 patient selection  254–255

contrindications  255 indications  254–255 stabilization methods  256

prism ballast  256 truncation  256

Toric soft lenses  263–275 designs  268–270

back surface torics  269–270 front surface torics  269

fitting  271–273

custom made lenses  271 disposable and stock torics  271 examples

back surface disposable toric  274–275

back surface disposable toric  274–275

front surface stock toric    273–275

front surface toric, full parameter range  273–274

routine  271–273 patient selection  263 indications  263

contraindications  263 stabilization  264–268

influences on lens behaviour  264 methods  264–267

accelerated (ASD)  266, 266f dynamic  265–266

lens rotation assessment  267–268 lens markings  267, 267f

lens orientation and rotation  268, 269t, 270f

prism ballast advantages  265 disadvantages  265

prism ballast  264–265 thin zones  265, 265f advantages  265

thin zones  265 disadvantages  265

toric back surface  267 truncation  266–267 advantages  266

disadvantages  266–267 Total diameter (TD)  133, 174, 176

PMMA  361

silicone hydrogel  207, 228 soft lenses  189–192

semi-scleral  312, 316–317 and zone diameters  164

Transition  415

Translation  415 Transmissibility see under Oxygen Trial lens  51, 415

decontamination and disinfection  47, 51–53

disposable  223–224 , 271–273, 342 in instruments  23

Tricurve lens  126, 415 constant axial edge lift  126f tear layer profile  127f

Truncation  415 Tscherning aberroscope  31 Types

patient’s suitability for rigid gas-permeable

new patients  73–74 refits/previous failures  74

rigid gas-permeable  73–74 silicone hydrogel  73

Upper Lid Margin Staining (ULMS)  85

V gauge  164

Vascularization  232, 248–251, 415 Veterinary lens  395

Viral keratitis  348 Viscoelastics (thixotropic)  88 Viscosity agents  307

Vision alternating  405

monovision see Monovision overnight correction (OVC)  169 simultaneous  291, 363, 414

Visual acuity (VA)  33 Visual problems  329–331

general factors  329–331 distance vision  330 adaptive  330 non-adaptive  330

intermediate vision  331 near vision  330

rigid gas-permeable lenses  331 soft lenses  331

see also Wearing problems Vividrin  50–51

Warpage, corneal  29–30, 360 Water  48

content  415

content and uptake see under Materials sterile  48

tap  48 uptake  415

see also Wettability

Wavefront technology and ocular aberrations  205

Wearing problems  331–341 blinking  341

bulbar conjunctiva  337 injection  337

cornea

air bubbles (dimpling)  335–336 foreign body  335, 335f, 409 mucin balls  336

oedema  332 staining  332–336

3 and 9 o’clock  333–334, 333f arcuate  332–333, 332f central  334, 334f

irregular  335

punctate (corneal stippling)    334–335, 334f

diffuse  334f ’donut’  335f inferior  334f

environmental/general factors  340 general factors  331

lens adhesion  339–340 lids  337–339

lens-induced papillary conjunctivitis  337–339

limbus  336–337 blood vessels  336

Dellen (Fuch’s dimple)  337 limbal opacification  337 pinguecula  337

staining  336–337

miscellaneous  339 other factors  342

assessing lens condition  342 reassessing lens refraction and fitting   

342 solutions, use of   342

ptosis  339

yearly intervals or longer  341–342 ocular examination  341–342

conjunctiva  341 lids  342 over-refraction  342 tears  342

Websites, useful  401–404 dry eye  404

general interest  403 investigative techniques  404 journals  401–402 ophthalmology  404 professional  403

teaching resources  402–403 technology  403–404

Weicon ce lens  207–208 fitting technique  208 geometry  207–208

parameters available  208, 208t related lenses  208 specification, typical  208

Wettability  76, 92, 415 Wetting agents  92

Wetting solution  306, 315, 415 White light assessment see under Fluorescein patterns

Xerogel  415

Yellow card reports  41

‘Z’ factor see radial under Edge lift Zeiss (Oberkochen) mires  22f Zernicke analysis  30–31

Zero 6 lens  206–207

fitting technique  206–207 geometry  206

material properties  206 parameters available  206, 207t related lenses  207 specification, typical  207