Recent Advances in Ophthalmology–14 HV Nema, Nitin Nema
Page numbers followed by ‘f ’ and ‘t’ indicate figures and tables, respectively.
Abbott Medical Optics 117
Aberrometry-guided devices 125, 132
continuous loop fixation 190
four-point fixation with haptic looping 191
insertion of suture 189
scleral fixation 190
technique, subsequent variations 189
two-point fixation 190
depth 8
ratio 8
Acetylcysteine 303
AcrySof IQ PanOptix IOL 117
Acute retinal necrosis syndrome 276
Adeno-associated viral vectors 297
Aflibercept 217, 227, 228
after ranibizumab intravitreal injections 2 226
treated cases 269
Age-related eye disease study 227
Age-related fibrillopathy 135
Age-related macular degeneration 53, 116, 211, 222, 226, 227
trials of treatment 224t, 226t, 227t
capsule tension segment 173, 174, 174f, 175
CT segment 176f
glaucoma valve 80, 80f, 84f
various models of 80t
segment, steps of scleral fixation of 182f
Air pump assisted technique 29f
Akreos lens 195
Aladdin HW3.0 95, 96f
Albinism 46
Alpostadil 228
American Academy of Ophthalmology 1
American Society of Cataract and Refractive Surgery 1, 108
Amniotic membrane application 304f
Anacetrapib evaluation effects of 215
Angioanalytics 242, 243f
use of 248f
Angioarchitecture of fistulous lesions 310
in retinal diseases 236
machine 310
AngioVue OCT angiography software 240, 240f
Aniridia 76f
with glaucoma 77
Anterior assisted levitation 165
Anterior chamber 135
depth 90, 112, 136
intraocular lens 167f
sudden deepening of 160f
Anterior lamellar keratoplasty, recent advances in 32
Anterior segment optical coherence tomography 5f, 150, 151f
Anterior vitrectomy 185
Antiangiogenic factor 264
Anti-infective agents 283
Anti-vascular endothelial growth factor drugs 214
Aphakia 91
eye blocked 87f
glaucoma 76
refraction 108
incision 119f, 120
keratotomies 123
Argon laser trabeculoplasty, treated eyes 67
Argos 97, 97f
Arrestin gene 291
access 311
and vein occlusions 53
dissections, causing 312
thrombosis 312
fistula 312
malformation 310, 317f, 319f
passage time 55
Artifact 241
corrected by software 242f
correction of motion 241
movements 242f
projection 242
white line 242f
intelligence-based formulae 103
pupil 50
Aspirin 280
Assisted levitation
anterior 169f
posterior 169f
Assort toric calculator 105
Astigmatic effect of surgical incision 126
correct preexisting 117
location of incision to reduce 118t
management in cataract surgery 123
minimize postoperative 117
Atherosclerotic disease, severe 310
Aurolab aqueous drainage implant 78, 79f, 83f
Autoimmune diseases 12
Autologous 303
limbal transplantation 306
Autosomal recessive 288
Baerveldt implant 78, 85
various models of 78t
Balanced salt solution 28
formula 130
toric calculator 106
True-K formula for IOL power calculation 109
universal 2 102
Baylor nomogram 130
Beiko and Steinert technique 202
Belin/Ambrósio enhanced ectasia 9, 10f
Bevacizumab 217, 222, 224, 227
eliminates the angiogenic threat 224
treated cases 269
Bimanual irrigation and aspiration 164
Binkhorst regression 97
Bioimaging biomarkers 268269
Biomechanical elasticity theory 11
Biometry 90, 112
Bioptics 123, 131
Blood-retinal barrier, outer 264
Blunt trauma 171
Branch retinal vein occlusion 211, 222, 246, 248
evaluation of efficacy and safety 222
Branched retinal artery occlusion 247
vascular network 255f
Brimonidine 228
Brown's syndrome 85
Bruch's membrane 239
Bubble, types of 25f
Burst mode power modulation 114f
Calcium channel blockers 64
Callisto 93f
Camellin-Calossi for postrefractive eyes 97
Candesartan 213
Cannula-based intrascleral tuck 203
Capillary dropout 239
nonperfusion 277
phase 315f
Capsular bag 172f
devices 174f
fibrosis 199f
IOL complex, late spontaneous dislocation of 199f
support, choice of 77f
Capsular hooks 172
with long blunt loop 173f
Capsular support device 179
for subluxated lenses 171
Capsular tension ring 141, 177
insertion steps 181f
assessment of 166f
careful assessment of 164
retractors 143
tension ring 173
different sizes of 175
insertion, technique of 180
tension segment 142
Capsulorhexis 140, 178
construction 127f
strategies for 179
Carcinoma-associated retinopathy 287
Cardiovascular risk in type 2 diabetes 213
Carotid artery
external 311, 313
internal 311
left internal 320f
right external 313
right internal 314, 315, 316, 317, 317f
Carotid-cavernous fistula 310, 320f
density 136
postvitrectomy 159f
surgery 90, 112, 121, 123, 156, 320
Cell division theory 68
anterior vitrectomy 164
corneal thickness 96
macular subfield thickness 216
permanent tarsorrhaphy 304
retinal vein occlusion 211, 221, 222, 246247, 249
serous chorioretinopathy 254
case of 256f
subfield thickness 217, 218, 268
subfoveal 262
vein occlusion study 222
Cerebral angiography 312f, 321
3D-digital subtraction angiography 315
advances in 315
case studies 317321
complications 312
contraindications 310
in neuro-ophthalmology 309
indications for 310
preprocedural workup 310
procedure 311
role of 309
used for 312
Cerebral arterial metameric syndrome 319f
Cerebral artery, left middle 321f
Champagne bubbles 70f
Chemical burns 76
Chikungunya retinitis 282
mimic herpetic 282
Choriocapillaries 241, 254
Chorioretinal lesions 283
Choroid 250f
Choroidal dystrophies choroideremia 288
Choroidal effusion 85
Choroidal neovascular membrane 226228, 254
complex, size of 254f
Choroidal neovascularization 226227, 239, 253, 283
type I, type II, type III 253
Choroideremia 293, 296
with stellate macula 294f
Cicatricial pemphigoid 76
Ciliary neurotrophic factor 228, 297
Ciliary processes 135
Ciliary sulcus 189
fixation 186
position of 197
sclerotomy 200
Cilioretinal artery 249f
Cionni ring 173, 174f, 175
Coaxial irrigation aspiration 164f
Collagen cross-linking 12
for management of 14f
Collateral formation 246
Color Doppler imaging 55
advantages 56
limitations 56
imaging machine 55f
Cone-rod dystrophy 292
chorioretinal scarring 283
glaucoma 45
stationary night blindness 287, 288, 290
Conjunctiva 88f, 302
mobility 80
limbal autografting 306
Conjunctival peritomy 200
Contact lenses 13
Continuous curvilinear capsulorhexis 140
Continuous mode power modulation 113f
Contrast-induced renal failure 312
Copaxone 228
Cornea for severe ocular burns 304f
asphericity 6
astigmatism 123
preoperative assessment 123
surgical methods for treating 126
calcification 45
edema 205
severe 24
endothelial cell 199
evaluation 135
hydrops, acute 32
incisions 127f
infection 12
irregularities 49
neovascularization 45
pachymetry 47
patch graft 82f
power 112
stroma in isotonic 12
thickness spatial profile 9
tomography measures global corneal astigmatism 124
topography 4f, 6, 7f, 16, 18f, 47
touch and decompensation 89
vascularization 305
aspiration 180
cleaving hydrodissection 179
material, removal of 140
Cosmetic keratopigmentation 45
case 45, 48f
Cultivated limbal epithelial transplantation 306
Cycloplegic agents 303
Cyclotorsion 124
Cylindrical correction of toric IOL 121
Cystitome depresses 178f
Cystoid macular edema 89, 156, 157f, 195, 205
development of 196
Cytomegalovirus 274, 275, 276, 279
intravitreal therapy 282
retinitis 274, 280, 281f
treatment 282
Debris, tube blocked 88f
Deep anterior lamellar keratoplasty 23
Deep capillary plexus 241
Deep inner retina OCT angiogram segmentation 241
Deep layer 249
Deeper en face angiograms 242
ophthalmic complications 283
related foveolitis 283
virus retinopathy 283
Deoxyribonucleic acid viruses 274
Descemet's membrane 35
endothelial keratoplasty 23
Descemet's stripping automated endothelial keratoplasty 23
Diabetes control and complications trial 213
Diabetes mellitus
control of 212
prevalence of 260
Diabetic macular edema 211, 213, 214, 215, 216, 220, 269, 269f, 270f
antivascular endothelial growth factor 214t
bilateral 218
bioimaging biomarkers in 268
lasers in 214t
patient compliance 219
SD-OCT-based morphological classification of 266
trials with corticosteroids in 216t
Diabetic maculopathy 214
Diabetic patient with moderate NPDR 245f
Diabetic retinopathy 211, 212, 213, 243, 260
candesartan trials 213
clinical research 214, 215, 216, 220, 221
occurrence/progression of 213t
study 220
study, early treatment for 214
systemic factors 213t
vitrectomy study 221
Diamond calibrated knife 41f
Diffuse corneal opacity 46
Diffuse slit lamp examination 137f
Diffuse subarachnoid hemorrhage 316f
Diffusion weighted imaging 321f
image-guided systems 126
subtraction angiography 310
Disability affected life years 17
Dislocated capsular bag-IOL complex 199f
corneoscleral graft 24
scleral patch graft 84f
tissue for allogeneic limbal transplantation 306
Doppler optical coherence tomography 59
advantages 59
limitations 59
Doppler velocimetry 53
Drainage devices, current 77
Drug toxicity 295
Dry age-related macular degeneration 223, 252
Duke-Elder's classification 147
Dural arteriovenous fistula 310
Ectasia cases 7
Ectropion 305
Edema, resolution of 36
Efficacy versus effectiveness 211
Ellipsoid zone 263
Ellipsoid zone, classification of 263
Emphysema 34
En face OCT 247f
Enalapril 213
End-diastolic volume 55
Endocapsular placement 184
Endoilluminator-assisted descemet's membrane endothelial keratoplasty 24, 26f
Endophthalmitis 89, 156, 157f, 195, 197, 205
Endoscopy-assisted scleral-fixated IOL 191
Endothelial keratoplasty 23
recent advances in 23
Endovascular procedures 317
Enface optical coherence tomography 267, 268f
advantages of 267
Enface thickness maps 267
Entropion 305
Epinuclear plate 154
Episcleritis 277
Epithelial downgrowth 77
Epstein-Barr virus 274
Ethylenediaminetetraacetic acid 45
Excessive conjunctival scarring 76
External limiting membrane 263, 265f, 270
blood 196
needle-guided haptic insertion technique 203
Exuberant vascular proliferation 246
Eyelid malpositions 305
EyePro application 109
chronic rubbing of 9
undergoing penetrating keratoplasty 197
Eyestar 900 98, 99f
Famciclovir 279
Femto laser-assisted arcuate keratotomy 119f
Femtodelineation technique 152, 153f
Femtosecond laser 112, 128
Femtosecond laser-assisted
arcuate keratotomy 117, 118, 129f
cataract surgery 147, 149, 150
intrastromal keratopigmentation technique 43f, 44f
Fenofibrate 213
intervention 213
Fetal posterior cerebral artery 313f
Fibrinous membrane 87f
Fibronectin 131
Fibrovascular pannus formation 305
Finesse flex loop 203
Fish-tail technique 173
Flaccid bag taut 175f
Flap replacement surgery 16
Fluocinolone acetonide intravitreal implant 216t
Fluorescein angiography 244246, 248
Fluorescein staining of ocular surface 304f
Focal disruption 264f
Foci of retinal necrosis 275
Food and Drug Administration 60
Fornix based conjunctival flap sutured 84
Foscarnet 279
avascular zone 246
retinal inner layers 269
Fuchs’ dystrophy 45, 116
albipunctatus 291
evaluation 46
fluorescein angiography 249, 277
typical retinitis pigmentosa 289f
xerophthalmicus 292
Galilei G6 97f, 98
Ganciclovir 282
Ganglion cell
complex 61f
layer 241, 262
Gaussian optics assumes 104
Gene therapy 297
in pregnancy 68
primary 138
secondary 156
Glaucoma drainage devices 74, 75, 86f, 87f
choosing 81
indications of 76f
types of 74
Glaucomatous eyes 55
Global disruption 264f
intraocular lens 168f
intrascleral haptic fixation 200
IOL, sutureless 201f
Goldmann three-mirror goniolens 69
Gore-Tex suture 192f
Graft injected into anterior chamber 30f
Gyrate atrophy 293, 294f, 296
Haigis 101
Haigis-L formula 107
Handshake technique 200, 202f
double suture fixation to 190
eyelet 192f
looping method 190
tucked, tunnel 201f
Headache, sudden severe 317
Hemoglobin A1C 213
Henderson capsule tension ring 174f
Hepatitis B surface antigen 310
Herpes simplex viruses 274
Herpetic phase, acute 277
Herpetic retinitis 274
Herpetic retinopathies 275
features of 279t
Hill-RBF calculator 103
Hoffer-Savini LASIK IOL power tool 108
Hoffman elbow 85
Hoffman's pouch 194f
dissection of 194f
IOL consultant toric preoperative planner 106
Schema-9, types of eyes 103t
Homocystinuria 171
Host Descemetic scaffolding 31, 31f, 32f, 33f
Human immunodeficiency virus 274, 310
Hybrid lens 13f
Hydrodelineation 149f
Hydrodissection 140, 179
Hypertension in diabetes study 213
Hyphema 85
Hypotony 85
early postoperative 79
maculopathy 89
postoperative 204
Iluvien acetonide 228
Implants, functioning of 74
Indocyanine green 53
angiography 236
investigations with 223
Inferonasal quadrant 86f
Inferotemporal BRVO, case of
Inflammation, types of 274
necrotizing 274
non-necrotizing 274
Informed consent 310
Injectable suture device 190
Internal limiting membrane 239
Interventional radiology 309
gas 32
tube 81
Intracapsular cataract extraction 186
Intracorneal ring
segments 14
segments management of 15f
Intractable glaucoma shunts 74
complications 85
management of 74
placement of tube 85
preoperative evaluation 80
site of implantation 85
surgical procedure 81
use of antifibrotics 85
Intralamellar keratoplasty 16
Intraocular ab-externo suture fixation 190
Intraocular inflammation 282
Intraocular lens 184, 288
first implanted in 1949 90
fixation 143
implantation 95, 164
sutured scleral-fixated 168f
insertion 181
Master 500 93, 93f
Master 700 94, 95f
positioning 127f
power 186
calculation 130
classification 101
formulae 100
in eyes 107
recent advances in 90
secondary 23
selection 115, 143, 199
for scleral fixation 185
single piece 167f
three piece 167f
types of 185
Intraocular pressure 53, 67, 74, 199
lowering drugs 64
Intraoperative aberrometry 99, 108
floppy iris syndrome 115
sutureless haptic fixation, surgical technique of 199
tunnel 200
corneal dissectors 41f
keratopigmentation 42
instruments of 41f
tunnel 50
antiviral therapy 280
triamcinolone acetonide 214, 216, 222
vascular endothelial growth factor 253
Iridocorneal endothelial syndrome 46, 76
Iridodialysis 46
claw lens 143, 168f
coloboma 39, 46, 49
cysts, progressive 46
hooks 171, 172f
retractors 180f
Ischemic maculopathy 283
Ischemic retinopathies, cases of 242
Jacob technique 32
for primary pre-descemetic deep anterior lamellar keratoplasty 36f
Joseph valve 74
Keratitis 277
Keratoconus 5
Keratocyte density, loss of 11
Keratometry 93, 124
Keratopigmentation 4546
complications 49
contraindications to 47
device for superficial automated 40f
functional therapeutic 47f
indications 45
innovative surgical option for 39
instruments 40
pigment selection 40
practice of 39
surgical techniques 42
technologies 40
therapeutic functional 46
Keratoplasty 16
Keratoprosthesis, type-1 307f
Knot erosion 193
intraocular lens tilt 193
use of scleral flaps 193
use of scleral grooves 193
Koch nomogram 118
implants 79
valve 74
Kyriele's plaques 281
Ladas super formula 102
Lagophthalmos 305
Lamellar keratoplasty, recent advances in 23
Lamellar scleral flaps 189, 202f
dissection of 201f
Lamellar scleral graft 196f
Lampalizumab 228
Laser Doppler flowmetry 53, 58
advantages 58
limitations 58
Laser Doppler velocimetry 57
advantages 57
limitations 58
Laser in situ-keratomileusis 131
Laser photocoagulation 223
Laser speckle flowgraphy 54
Laser-assisted in situ keratomileusis 1, 112
Lasers in glaucoma, role of 67
Lens fragmentation 152
Lens touch 87f
Lenstar LS 900 94, 94f
Leukomatous corneas, management of 39
Lid margins 302
Limbal groove 199f
incision 190
Limbal relaxing incision 123, 117118, 125, 128
Limbal stem cell deficiency 302, 305f
Limbal transplants visible on ocular surface 306f
Lipid-modification 215
Lisinopril 213
Loading dosage 217
Lock-and-lead technique 203
Losartan 64, 213
Low-density lipoprotein 213
Lutein antioxidant supplementation trial 227
Lymphoma 276
MacTel stage 5 252f
Macular edema
assessment of implantable dexamethasone 216
due to retinal vein occlusion 222
Macular telangiectasia type 2 248
Macular thickness map 270f
Magnetic resonance imaging 49
Malyugin ring 140
Manual intrastromal keratopigmentation 42
Manual small incision cataract surgery 140
Marfan syndrome 171
Masket method 107
modified 108
Matrix metalloproteinase 11
Maximum intensity projection 316
McCarthy post refractive IOL calculator 109
Mean dye velocity 55
Melanoma-associated retinopathy 287
Melles technique of optical recognition 35f
Mesenchymal stem cells 297
Michelson interferometer 92
Microaneuryms and vascular beading 244f
Microaneurysms development of 243
Microbial contamination 195
Microcatheters, use of 203
Microincisional cataract surgery
advantages in difficult situations 115
in customization, role of 115
Microkeratome-assisted LASIK 132
Microkeratome intraocular pressure 132
Micronized mineral pigments 41
advantages of 41
Microrhexis forceps 158
Microsurgical technology 172
Microvascular abnormalities 246
Microvitreoretinal forceps, using 23-gauge 194f
Middle cerebral artery 313
Migraine 63
Minimal pre-descemetic stroma 35
Missed ectatic pathologies 16
Mitomycin-C 85
Mixed keratopigmentation 43
Miyake-Apple view 175f
Mizuo phenomenon 291, 292f
Molteno implant 77
various models of 77t
Morcher capsule tension ring 174f
Motility disturbances 85
Moxaverine 228
Multifocal intraocular lens 116, 116f
Multifocal IOLs 117
Myopia, high 8
Necrotizing retinopathies 274
clinical features 276
etiology 276
Neodymium:yttrium aluminum garnet laser 67
age-related macular degeneration 211, 223
complex 243f
glaucoma 68, 76
case of 85
tuft 245f
Nerve fiber layer 239
Neural progenitor cells 297
Neuroprotective agent 297
Neuroprotector 228
Neuroretinal changes, signs of 262
Nidek claims 96
Nifedipine 64
Night blindness 297
Nitinol flex loop 203
Noncontrast computed tomography 316f
Nonfoldable polymethylmethacrylate 129
Nonproliferative diabetic retinopathy 243244
Nonsteroidal anti-inflammatory drug 71, 143
Normal tension glaucoma 55
Nuclear layer, inner 239, 241
Nuclear sclerosis, grade of 114
Nucleus drop 165, 169f
Nucleus management 170
Nuijts-Solomon bubble marker 125f
Nyctalopia 287
approach to patient of 296
classification and causes of 287
clinical features of specific disorders causing 288
etiology 287
pathophysiology 295
treatment 296
OA 2000 99, 99f
Occlusive vasculopathy 275
OCTA machines 237t
Ocular blood flow
assessment of 53
factors affect 62
pharmacological 64
physiologic 62
systemic disease 63
in glaucoma 53
techniques for measuring 54t
Ocular burns
acute 304f
classification of 303t
emergency 302
management of 302
practical approach 302
vision restoration after severe 305
examination 296
hypertension 64, 68
infections 45
check-up for dry eye 46
diseases 76
reconstruction 305
vascular dysregulation 63
Oguchi's disease 291, 292f
Ohta Y-fixation technique 202
ray-tracing methods 94
uses ray tracing optics 104
Olsen formula 104
Open angle glaucoma 68, 77
primary 68
secondary 68
artery, right 317
viscosurgical device 178
Ophthalmological assessment 46
atrophy 283
disk 61f, 281f
nerve head 53
blood flow of 64
Optical biometers 91, 92
advantages of 91
disadvantages of 91
Optical coherence tomography 199, 226, 236, 250, 289f
angiography 59, 236, 240f, 244, 246, 248250f, 254256
advantages 62
amplitude-based 238
complex signal-based 238
correlation 61
development timeline 60f
image processing 239
limitations 62
normal eyes 240
phase-based 237
principle of 236
quantification of 239
retinal disorders 243
in diabetic retinopathy 260
signal 241
Optical low coherence reflectometry 9192, 123
Optical microangiography 60
refractive analysis 100
quantification tool 242
Orbital region, right 317
Oregon Health and Science University 60
Ozurdex study 217
Pachymetry, preoperative 7
Panretinal photocoagulation 220, 222
Paraneoplastic retinopathy with carcinoma 294
Parenchymal abnormality 321f
Pars plana
clip 85
infusion cannula 200
phacoprosthesis 191
20-gauge vitrectomy 202f
vitrectomy 166f, 270
Partial coherence interferometry 9192, 112
Patent iridotomy 68
Peak systolic velocity 55
Pegaptanib sodium 227
Pellucid marginal degeneration 5
Penetrating keratoplasty 23
Pentacam AXL 97, 98f
Peribulbar block 81
Periocular skin 302
Peripapillary retina 281f
cornea 199f
corneal 128
relaxing incisions 117
iridectomy 29
retina 275, 281
zone 137
Periphlebitis 277
Perivascular retina 278
Persistent epithelial defects 305
Petrosal sinus, superior 320
Phaco probe 163
removal of 163f
Phacodonesis 137, 176
Phacoemulsification 138, 176, 177, 179, 184
in subluxated lenses 171
stage of 114
surgery, development of 112
technique 140
Phacooptics 105
Phakic intraocular lenses 45
Phosphodiesterase inhibitor 228
Photic phenomena 49
Photodynamic therapy 223, 226
Photorefractive keratectomy 8
Phthisis bulbi 46
Pial arteriovenous fistula 310
Pigment clumps 251f
Pigment epithelial detachment 253, 256
Pigment epithelium derived factor 264
Placido-disc measure 124
Plate erosion 85
Plexiform layer
inner 239, 241, 262
outer boundary of 239, 241
cells 68
stem cells 297
Pneumodescemetopexy 34
Polymerase chain reaction 276
Polymethyl methacrylate intraocular lens 192f
Polymethylmethacrylate rings 173
Polypoidal choroidal vasculopathy 223, 254
Post corneal refractive surgery 107
Postcerebral angiogram 321f
Posterior assisted levitation 165
Posterior capsular
defect 151f
rupture 156
anticipation of 158
early signs of 156
important clinical pearls 158
improperly managed 156
management 156
prevention of 158
recognition of 156, 158
stages 156
tear 162f
Posterior capsule rent 115
Posterior capsulorhexis 160f
Posterior chamber intraocular lens 199, 200
Posterior corneal astigmatism 124
Posterior fossa parenchyma 313f
Posterior polar cataract 147, 150, 159f
case of 152
classification of 147
phacoemulsification in 148
timing of surgery 148
Post-laser-assisted in situ keratomileusis ectasia 2f, 4f, 5f, 13
Post-LASIK ectasia
common clinical findings 2
epidemiology 1
grading system for 6t
histopathology 11
investigations 2
management 12
management of 1
pathogenesis 9
presenting features 2
prevention 16
risk factors for 5
Power modulation 113
burst mode 113
continuous mode 113
pulse mode 113
Precise capsulotomy, creation of 150
Pre-Descemet's endothelial keratoplasty 23, 24
air pump assisted 27, 29f
graft 31f, 33f
DALK for acute hydrops, modified tecnique 32
dissection for acute hydrops 35f
Pregnancy period 12
Premacular hyaloid growth factor reservoir 261
Premium intraocular lenses 123
Proliferative diabetic retinopathy 213, 219, 245f
clinical trials on 220t
Prophylactic laser 280
Pseudoaneurysm 312
Pseudodispersive viscoelastics 139
Pseudoexfoliation 68, 171
and cataract surgery 138
cataract: management 135
deposits on
intraocular lens 144f
pupil 137
endothelial deposits of 135
eyes 138
glaucoma 76
postoperative complications 143
preoperative evaluation 135
syndrome 135
Pseudonight blindness 287
Pseudophakia 91
eye 85
glaucoma 76
Pseudoplasticity phenomenon 178
Pulsatile ocular blood flow 54
Puncture site hematoma 312
Pupil optic zone markers 41f
Pupil size 136
constriction 150
margin 135
ruff 136
stretch with Kuglen hooks 139f
Radial keratotomy 112
Radial superior incision 44f
Radiation therapy for age-related macular degeneration 226
Randleman's ectasia
risk factor score system 6t
score 8, 17
Randomized controlled trial 221
Ranibizumab 220, 221, 222, 226, 227, 228
for choroidal neovascularization 222
for diabetic macular edema 215
for the treatment of macular edema 222
treated cases 269
Rapamycin 228
Rapid progression 275
Real-life situation 212
Refraction-based formulae 101
Refractive targeting 112
Refractory infantile glaucoma 77
Reftinal detachment 157f
Regression formulae 101
inhibitor 64
system study 213
Residual stromal bed 56
Retina, outer 252
angiomatous proliferation 253
arteriovenous malformation 318
artery occlusion 247
detachment 89, 156, 195, 205
mechanism of 278
secondary 276
hemorrhage, large areas of 275
implants 297
layer: inner 262f
disorganization of 261
outer, disruption of 263
macular degeneration, late-onset 294, 287
necrosis: acute 274, 275, 276, 279
active herpetic phase of 275f
surgical management of 280
necrosis: outer, progressive 274277, 279
diagnosis 278
treatment 279
nerve fiber layer 60, 262
defect 61f
loss, inferior 64f
layer thinning of 268
oximetry 53, 58
advantages 59
limitations 59
pigment epithelium 53, 239, 251f, 264f, 288
thickness 262
transvitreal oxygenation, improvement of 261
vascular disorders
message from clinical trials 211
real life situations management of 211
vasculitis 282
vein occlusion 211, 220, 246
vessel analyzer 53, 54, 58
advantages 58
limitations 58
Retinitis pigmentosa 287, 288
atypical form of 290, 291f
typical 289, 289f, 290f
Retinopathy of prematurity 211, 223, 224, 224t
Retrobulbar hemodynamics 64
Retrogeniculate damage 283
Rheological factors 63
Rhexis in weak zonules 178f
Rhodopsin gene 288
Rhodopsin kinase 291
Riboflavin solution 12
Riggs type 290
Rigid gas permeable 12
Rod photoreceptors 287, 288
Scanning laser ophthalmoscopic angiography 53, 54
advantages 55
limitations 55
Scarred limbal area 81
forceps 200
technique 200
Scheimpflug imaging 96
dual 98
Schlemm's canal 68
Schocket procedure 77
Schroeder classification 148
Schubert-Bornschein type 290
Sclera-corneal incision 128
Scleral fixation
devices 173
Gore-Tex suture for ab-externo four-point 194f
in small eyes 197
intraocular lens 184
implantation in children 196
modification in materials for 192
sutures, techniques of 188t
two-point ab-externo 192f
with Cionni ring, technique of 180
flaps 190
lens 13f
sutured IOLs, surgical techniques 187
Scleritis 277
Sclerocornea 46
Sclerotomies 200
Segmental retinal periarteritis 281
Selective laser trabeculoplasty 67, 69, 71, 72
advantages 68
complications 71
contraindications 68
disadvantages 68
indications 68
laser 70f
mechanism of action of 68
principle of 67
technique 69
Setons, glaucoma drainage devices 74
Shaded surface display 316
Shunts nonrestrictive 74
Shunts nonvalved 74
Siderosis 295
Silicone oil-filled eyes 91
Silicone tube 77
Simple limbal epithelial transplantation 306
Singh's classification 148
Single-piece rigid polymethyl methacrylate lens 186
Sinskey hook 28
using 194f
Slit lamp
examination 137f
marking 125f
Slit scanning corneal topography 123
Small incision cataract surgery 140141
steps of 141
Small incision technique 189
Small posterior capsular tear 158
Small pupil 139
Spectral domain-optical coherence tomography 260, 261f, 262f, 264f, 265f, 266f
analysis in diabetic retinopathy 260
Spinal vascular malformations 310
Split-spectrum amplitude-decorrelation 249
angiography 60
Staar Toric IOL 119
Standard care vs corticosteroid for retinal vein occlusion 222
Static zonulopathy 141
Steroid induced 68
Steven-Johnson syndrome 76
Stromal lamellae 11
Sturge-Weber syndrome 77
Subconjunctival hemorrhage 282
Subluxated lens 142f
surgical procedure 176, 177
Suboptimal visual 130
Subretinal hemorrhages 253
Subtenon's anesthesia 81
Subtle retinal edema 281
Superficial and deep layers 251f
Superficial anterior lamellar keratoplasty 23, 42
technique 43f
Superficial capillary plexus 243, 244
Superficial keratopigmentation 42
Superficial manual keratopigmentation 42
Superficial vascular plexus 241
Superotemporal quadrant 85
Suprachoroidal hemorrhage 85, 195196
Surface ablation, advanced 8
Suture erosion 195
Suture knot erosion 196f
Suture-assisted sutureless technique 202
Sutured scleral fixation 184
intraocular lenses 165, 195, 197
Sutured vs sutureless scleral fixation 205
Sutureless intrascleral haptic fixated 197
developed technique of 197
Sutureless scleral fixation
intraoperative complications 204
postoperative complications of 204
Suture-related modification 192
Swept-source OCT 60, 92
Sylvian fissure, right 316
Systemic corticosteroids 280
Tandospirone 228
multifocal IOL 117
toric IOL 119
Telangiectasia 246
Telecentric keratometer 95
cyst 89
tissue growth 77
Tissue necrosis factor, administration of 303
Topcon's Aladdin HW3.0 95
calculators 106
intraocular lens 119, 129
calculators 105
implantation 120
stability of 130
Torn zonules 171
Torsional (OZil) 114
Trabecular meshwork 67, 135
Trabeculectomy 77
Trabeculoplasty lens 69f
Tracey technologies 126
Tractional retinal detachment 283
loss of consciousness 317
vitreous hemorrhage 205
iris 46
rendering 316
Transmission electron microscope 11
Transscleral fixation 186
in children 198t
cataract 158, 159f
glaucoma 68, 76
Triamcinolone, uses stain vitreous 165f
Trimetazidine 228
Tube exposure 88
Tube retraction 85
Tucked-in lamellar keratoplasty 16, 23
Tunica vasculosa lentis 147
Two-handed technique 201
Two-instrument iris stretch 139
amplitude scan, first performed in 1956 90
biomicroscopy examination 187
customization 114
United Kingdom Prospective Diabetes Study 213
Universal Serial Bus 93
Universiol calculator 105
Urrets-Zavalia syndrome 46, 49
Utrata forceps 158
Uveitic glaucoma 68, 76
Uveitis 85
Uyemura's syndrome 292
Valganciclovir 282
Valved implants 79
Varicella zoster virus 274
access 311
congestion 246
density 59
en face angiograms, percentage of 242
endothelial growth factor 220, 254, 264
lesion 310
sheathing 283
system visualization of 309
Vasospasm 63
Venous looping 246f
Vergence formulae 101
Verion planner 106
Vertebral artery 319f
right 318
Verteporfin in photodynamic therapy 226
Viral keratitis 16
Viscoelastic, injecting 163f
acuity 213
field 289f
Vitamin A deficiency 292, 293f
Vitrectomy 23
bimanual 161f
cutter 166f
for diabetic retinopathy-related vitreous haemorrhage 221t
technique 161
adhesion 261
interface analysis 260
traction 261, 261f
Vitreous hemorrhage 89, 195, 283
Wang-Koch modification for IOL formulae 105t
Warfarin 280
WaveTec Vision Systems 100
Waxy disk pallor 289f
Weak zonules 171
West Nile virus 282
retinopathy 282
Wet age-related macular degeneration 253
Yamane's technique 203
Zernike coefficient for spherical aberration 6
instability, signs of 138
weakness, adjunctive devices for 141
Zonulodialysis 171
Zonulopathy 171
Chapter Notes

Save Clear

Management of Post-LASIK EctasiaCHAPTER 1

Partha Biswas,
Sneha Batra
Laser-assisted in situ keratomileusis (LASIK) has become the gold standard for the treatment of refractive errors worldwide.1 Over time, the rate of complications has been seen to be extremely low.2 However, when these complications do occur, visual consequences can be substantial and patient dissatisfaction high, particularly because it is performed mainly as an elective cosmetic procedure, especially in young patients.
Post-LASIK ectasia (PLE) is defined as a region of abnormal steepening and increased curvature within a centrally flattened optical zone.3 There is associated biomechanical weakening of the cornea.4
Seiler documented the first case report of PLE in the year 1998,5 and it was thought at that time that an epidemic of iatrogenic keratectasia is looming over the world with increasing numbers of refractive procedures being performed worldwide without proper screening criteria in place. However, 20 years down the line, that fear has not been substantiated, and rate of PLE reported has remained low worldwide.6,7
Prevention and management of post-LASIK ectasia has remained a hot topic for debate, and following a famous trial in 2005 when a young man with PLE was awarded millions of dollars as compensation, a consensus group was formed by American Academy of Ophthalmology (AAO) and American Society of Cataract and Refractive Surgery (ASCRS), which enumerated the risk factors for eliminating high-risk candidates, and also certified that PLE may even occur in candidates without any known risk factor, and that it should not be considered negligence on part of the surgeon.8
The incidence of PLE has been reported as 0.01–0.66% in various studies.6,7 The mean duration from the initial laser procedure to detection is 15.3 months. A quarter of patients develop PLE within the first 3 months and at least half of them within 1 year of the laser procedure.9 The earliest case was reported within one week,10 while the latest was after 144 months.112
Post-LASIK ectasia was seen more frequently among males and in the younger age group, in patients with thin corneas and high refractive errors pre-operatively.9
Any case of post-LASIK myopic regression, particularly if accompanied by a change in corneal topography, should be regarded with suspicion. Such patients should be closely followed up for at least 6 months before a decision for an enhancement procedure is taken.
Common Clinical Findings
  • Progressively increasing refractive error (mainly myopia and irregular myopic astigmatism).
  • Progressively decreasing best corrected visual acuity (BCVA).
  • Stromal thinning (Fig. 1).
  • Anterior and posterior corneal steepening.
  • Vogt's striae (rarely).
Rare presentations in PLE include acute hydrops with perforated cornea,12 and a case of globe rupture secondary to trauma.13
  • Corneal topography (Figs. 2A to D).
  • Anterior segment optical coherence tomography (AS-OCT) showing ectatic changes (Fig. 3).
  • Ocular response analyzer (ORA) shows decreased ocular hysteresis.14
Randleman criteria for PLE is as follows:15
  • Inferior topographic steepening of more than or equal to 5 diopters (D).
  • Loss of more than or equal to 2 Snellen's lines of visual acuity.
  • Alteration in refractive error of 2 D (spherical or cylindrical).
zoom view
Fig. 1: Slit lamp photograph of a patient with post-laser-assisted in situ keratomileusis ectasia showing stromal thinning, ectasia, and scarring.
zoom view
Figs. 2A and B:
Padmanabhan et al. in their study suggested the following criteria as indicators of development of post-LASIK ectasia:16
  • Increasing myopic refractive error with decrease in BCVA.
  • An increase in magnitude of the highest anterior and posterior topographic elevation.4
zoom view
Figs. 2A to D: Corneal topography of a patient with post- laser-assisted in situ keratomileusis ectasia. (A and B) Refractive quad map of right and left eyes showing ectatic changes; (C and D) Belin/Ambrósio enhanced ectasia display of the same patient showing ectatic changes.
zoom view
Fig. 3: Anterior segment optical coherence tomography of a patient with post-laser-assisted in situ keratomileusis ectasia showing thinning and ectatic changes.
  • A shift of the location of the steepest point on the anterior cornea and that of the highest elevation of the posterior cornea towards the center of cornea.
  • A reversal of the corneal asphericity towards greater prolateness.
  • An increase in negative spherical aberration and coma.
They also devised a grading system for the management of PLE (Table 1).
In their historic study,9 Randleman et al. described the major etiological factors for PLE, and also devised the ectasia risk score system (ERSS) to identify the high-risk candidates before the laser procedure (Table 2).
Preoperative Topographic Pattern
In the overall subgroup analysis in the Randleman study, abnormal topography pattern was found to be the most significant factor. More than 40% of ectasia cases had grossly abnormal changes such as keratoconus and pellucid marginal degeneration (PMD).9 These are now considered to be absolute contraindications to LASIK with medicolegal implications (Fig. 4).
The following corneal topography patterns were considered:
  • Normal or symmetrical
  • Suspicious:
    • Asymmetric bow-tie:
      • Asymmetric steepening less than 1 D
      • No skewing of radial axis (SRA)
    • Inferior steep axis or SRA:
      • Significant SRA ± inferior steepening
      • More than or equal to 1 D of inferior steepening locally, but overall inferior-superior asymmetry (I-S) value less than 1.4.
  • Abnormal: Keratoconus, PMD, or forme fruste keratoconus with an I-S value of more than or equal to 1.4.
Residual Stromal Bed
Patients with PLE have been shown to have significantly lower residual stromal bed (RSB) thickness than controls.6
Table 1   Padmanabhan et al. grading system for post-LASIK ectasia.16
+1 to –1
– 1.1 to –5
– 5.1 to –10
<0 to ≥–0.5
<–0.5 to ≥–1
<0 to ≥–1
<–1 to ≥–2
(CDVA: corrected distance visual acuity; HPE: highest posterior elevation; Q: corneal asphericity; SE: spherical equivalence; Z°4: Zernike coefficient for spherical aberration)
Table 2   Randleman's ectasia risk factor score system (ERSS).9
Corneal topography
Forme fruste keratoconus
Inferior steepening/skewed radial axis
Asymmetric bowtie
Normal/symmetric bowtie
Residual stromal bed (µ)
Age (years)
Preoperative pachymetry (µ)
Preoperative refractive error (D)
>–12 to –14
>–10 to –12
>–8 to –10
– 8 or less
It has been studied that posterior stroma is biomechanically weaker as compared to the anterior stroma, due to the differential distribution of keratocytes. Hence, corneal tensile strength is seen to decrease after LASIK.
In the Randleman ectasia score, all RSB thickness values less than 300 µ were considered increasingly significant in 20 µ intervals. Moreover, it has been documented that up to 33% of eyes with attempted RSB thickness of 250 µ could end up having actual RSB thickness less than 200 µ. The variability of flap thickness has been seen to occur with both mechanical microkeratomes and femtosecond lasers. Hence, it is now said that intraoperative measurement of RSB thickness is critical. It was seen in a survey among members of the International Society of Refractive Surgery or AAO in 2004, that only 31% refractive surgeons routinely measure flap or RSB thickness during surgery.17
It is seen that ectasia due to low RSB thickness usually occurs in the central corneal region while inferotemporal ectasia is usually seen in missed cases of forme fruste keratoconus or PMD.187
zoom view
Fig. 4: Corneal topography showing ectatic changes suggestive of keratoconus—absolute contraindication for refractive surgery.
Why 250μ of RSB was Considered the Magical Cut-Off Number?
Andreasson et al.19 found the elastic modulus of the keratoconic cornea to be 1.6–2.5 (average 2.1) times less than that of a normal cornea. Using these data, Seiler et al.5 postulated that reduction in the load-bearing portion of a normal cornea from 525 µ to 250 µ (a factor of 2.1) might simulate the elasticity of a cornea with keratoconus and predispose to development of ectasia. This value coincides with Barraquer's early recommendation that a RSB thickness of at least 250 µ be maintained to prevent corneal ectasia after keratomileusis.20
When ectasia cases with and without topographic abnormalities were compared, age was the only other significantly different factor. Patients without abnormal topographies were significantly younger than patients with defined topographic abnormalities. In the Randleman study, patients younger than 30 years were seen to be at risk; however, no recommendation was made on the basis of age.
Preoperative Pachymetry
The refractive error, preoperative pachymetry and RSB are interdependent factors. In the ectasia score, corneas with less than 510 µ were considered to be at risk.8
High Myopia
In the Randleman study, patients with more than 8 D myopia were considered to be at risk. Pallikaris et al. had shown in their review that no subjects with a correction of less than –8 D or RSB more than 325 µ experienced ectasia.7 However, Amoils et al.21 showed that even low to moderate myopia between –4 D and –7 D could lead to PLE in the presence of other risk factors.
Condon et al.22 also showed that high myopia is not a risk factor provided other parameters are within normal limits. It may be that higher refractive error is mainly responsible for a lower RSB, which is the actual culprit for PLE.
Randleman's ectasia risk score was formulated using the above 5 parameters. It was shown to have 91% sensitivity and 96% specificity, and till date, it is used as the most reliable score to identify high-risk patients prone to develop PLE.
However, these risk factors are not absolute, and even after screening out high-risk patients based on this score, there is still a substantial percentage of patients developing PLE without seemingly being at risk. This has led to a number of other risk factors being postulated by other researchers such as:
  • Percent tissue altered (PTA): It is a novel metric devised by Santhiago et al.23,24 which predicts high-risk patients irrespective of their topographic patterns. It is calculated as:
     PTA = (FT + AD)/CCT, where FT: flap thickness; AD: ablation depth; CCT: central corneal thickness.
They showed that in a patient with normal corneal topography, PTA more than or equal to 40 was the most prevalent risk factor (97%), followed by age less than 30 years (63%), RSB less than or equal to 300 µ (57%) and Randleman ectasia score more than or equal to 3 (43%).
Compared to RSB or CCT values, PTA provides a more individualized measure of biomechanical alteration because it considers the relationship between total thickness, tissue altered through ablation and flap creation, and ultimate RSB thickness. PTA was shown to have higher prevalence, higher odds ratio, and higher predictive capabilities for ectasia risk than moderate to high ectasia risk score system values.
  • Ablation ratio: Brenner et al.25 devised a new metric, ablation ratio, which is calculated as:
    Ablation ratio = Ablation depth/Pachymetry
    It was shown to have the strongest correlation with post-LASIK ectasia spherical equivalence.
  • Ablation depth: The depth of ablation and increased intraocular pressure (IOP) were shown to be significant risk factors for post-LASIK ectasia in white rabbits.26 Tatar et al.27 also showed that deep ablation more than 75 µ is the most important risk factor for the development of PLE.
  • Choice of procedure: About 4% cases of PLE have occurred after photorefractive keratectomy (PRK), whereas 96% cases occur after LASIK.9 Dawson et al.28 reported that PRK, sub-Bowman's keratomileusis (SBK) and advanced surface ablation (ASA) cause lesser reduction in the biomechanical strength of the cornea.9
  • Multiple enhancements: Multiple ablations are also thought to be an associated factor.29 However, it is difficult to say whether it is a true risk factor or the progressive myopia in these cases was actually due to missed cases of early PLE.
  • Thicker flaps: Thicker flap weakens the biomechanically crucial obliquely-oriented anterior stromal layer predisposing to PLE.30
  • Chronic rubbing of eyes: It could be a contributory factor.31
  • Pregnancy: It may induce certain hormonal changes such as production of the hormone relaxin which can induce or exaggerate pre-existing PLE.32
  • Other risk factors: These include candidates with family history of keratoconus and male sex.
Belin/Ambrósio Enhanced Ectasia Display (BAD)33
Brazilian ophthalmologist Renato Ambrósio and Arizona's Michael Belin developed a new software incorporated in the Pentacam® machine, which uses imaging of both the anterior and posterior corneal surfaces, and uses elevation-based tomographic data, combined with pachymetric analysis to generate a more accurate screening criteria for refractive surgery. While the first set of images displays the elevation of the anterior and posterior surfaces of the cornea compared to the best fit sphere (BFS) over a central 8 mm zone, the second set of images (the enhanced elevation map) eliminates the ectatic portion of the cornea from the computation, which helps to accentuate the effect of ectasia even in minimal amount.
The lower two maps (subtraction maps) show a color coding (red/yellow/green) to differentiate between normal and ectatic corneas. The corneal thickness spatial profile (CTSP) and percentage thickness increase (PTI) graphs depict the progressive thinning of the cornea from the periphery to the thinnest point, and the percentage of increase from the thinnest point out to the periphery respectively. Ultimately, a D value (Belin-Ambrósio deviation value) is calculated, which is indicated in yellow (suspicious) when it is more than or equal to 1.6 standard deviation (SD) from the mean (Fig. 5A), and in red (abnormal) when it is more than or equal to 2.6 SD from the mean (Fig. 5B).
However, despite screening protocols with all the known risk factors in place, some patients still develop ectasia with no identifiable cause. It is now thought that an individual's intrinsic tensile strength of the cornea probably is the most crucial factor for the development of ectasia.3437
Post-LASIK ectasia can be said to occur when the tensile strength of an individual's cornea is lowered below a certain threshold which is essential to maintain the shape of the cornea. This can occur in the following three ways:38
  1. The cornea undergoing laser refractive procedure does not show any topographic changes, but is intrinsically weaker and prone to develop ectatic changes in the future.10
    zoom view
    Figs. 5A and B: Belin/Ambrósio-enhanced ectasia display map. (A) Belin “suspicious” with D value in yellow range; (B) Ectatic changes with D value in red range.
  2. The cornea undergoing laser shows subtle topographic changes, but seems to be stable clinically, and is weakened further by the laser procedure.
  3. The cornea undergoing laser was biomechanically normal preoperatively, but an excessive amount of tissue loss weakens it beyond its threshold.
11The chief alteration predisposing to PLE is seen in the anterior corneal biomechanics which precipitates thinning and compression of collagen fibrils, resulting in loss of global structural integrity.6
Randleman et al.39 described in detail the histopathological and ultrastructural changes in corneas affected by PLE. Specimens of cornea with PLE which underwent penetrating keratoplasty (PKP) were observed for histopathological changes under light microscopy, and the following features were observed:
  • Corneal epithelial hypoplasia.
  • Breaks in the Bowman's membrane, typically smaller than that seen in keratoconus.
  • Adequate thickness of the flap.
  • Adequate thickness of the hypocellular primitive stromal scar.
  • Reduced thickness of the RSB.
  • Large interlamellar clefts in the ectatic region of the RSB.
The specimens were also evaluated in 2.5% glutaraldehyde under transmission electron microscope (TEM), where the following changes were noted:
  • Reduced thickness of the stromal lamellae.
  • Reduced number of lamellae in the stroma.
  • Loss of keratocyte density.40
  • Reduced thickness of the collagen fibrils.41
  • Presence of aggregated microfibrils in the Bowman's membrane and stroma.
  • Degeneration of the proteoglycans within the collagen fibrils, which lead to degeneration of the fibrils themselves, causing disorganization of the lamellae.41
  • Wavy and distorted stromal collagen bundles, especially in the posterior corneal region.42
Immunohistochemistry and Other Novel Investigations
  • Increase in proteinases such as matrix metalloproteinase (MMP) 10 and 3 suggesting ongoing epithelial basement membrane lysis and remodeling.43
  • Alpha 1-proteinase inhibitor (α1-PI) and Sp1 expression are unchanged.44
  • In vivo confocal microscopy shows increased corneal dendritic cell density.
  • Tear cytokine analysis shows altered cytokines as in dry eye suggesting a possible inflammatory role in PLE.45
  • Significant elevation of MMP 9 and decrease in tissue inhibitor of MMP (TIMP) 1 in tear samples.46
Biomechanical Elasticity Theory14
The biomechanical theory postulates that interlamellar and interfibrillar slippage occurs postoperatively in those areas of the residual stroma which 12are subjected to maximum stress. This chronic phenomenon is termed as “interfiber fracture”.
Guirao, in his study, used the spherical thin-shell model to demonstrate that tissue removal from an intact cornea causes anterior shifting of the posterior corneal surface with an increase in its dioptric power.47
As mentioned earlier, the posterior cornea is biomechanically weaker as compared to the anterior stroma. The creation of an anterior flap disturbs this distribution as this vital part of the stroma no longer contributes to the biomechanical integrity of the cornea.23
Contact Lenses
Contact lenses can be used in the earlier stages of PLE. Rigid gas permeable (RGP) lenses are the most commonly used lenses. They are very similar to those used in keratoconus patients, and lenses are custom made for every patient.48
Rose K lenses have been specially developed for ectatic corneas, and are now one of the most commonly used lenses worldwide (Fig. 6A). Scleral lenses have also been used in PLE patients, especially for those with irregular corneas (Fig. 6B).49 They can be either semi-scleral (16–18 mm diameter), or full scleral lenses (18–22 mm diameter). Hybrid lenses with central RGP like features, and peripheral soft lens-like configuration, have also been developed, which have replaced piggyback lenses now (Fig. 6C). PROSE (prosthetic replacement of ocular surface ecosystem) lenses have also been tried successfully (Fig. 6D).50
Collagen Cross-Linking (CXL)
Collagen cross-linking is considered to be the gold standard treatment for progressive corneal ectasia, but it is associated with slow and painful recovery periods.4
The indications for CXL in case of PLE are as follows:
  • Increase in Kmax more than 1 D in 1 year.
  • Decrease in BCVA.
  • Requirement for altered contact lens fitting more than biannually.
The contraindications to CXL are as follows:
  • Thinnest pachymetry less than 400 µ.
  • Corneal infection.
  • Autoimmune diseases.
  • Pregnancy or lactation period.
The CXL protocol followed usually is the Dresden protocol51 which includes:
  • Removing the corneal epithelium over 8 mm under topical anesthesia.
  • Soaking the corneal stroma in isotonic 0.1% riboflavin solution every 3 minutes for 30 minutes.
  • Application of ultraviolet A light at 3 mW/cm2 irradiance and 5.4 J/cm2 dose for half an hour (Fig. 7).13
zoom view
Figs. 6A to D: Contact lenses used in the management of post-laser-assisted in situ keratomileusis ectasia. (A) Rose K lens; (B) Scleral lens; (C) Hybrid lens; (D) PROSE lens.
zoom view
Fig. 7: Collagen cross-linking for management of post-laser-assisted in situ keratomileusis ectasia.
  • Application of bandage contact lens for 3 days for rapid re-epithelialization.
  • Antibiotic and steroid eye drops are given postoperatively.
Collagen cross-linking has shown long-term stability without significant side effects, and over time, it improves BCVA, decreases cylindrical power and Kmax values, and halts progression of topographic indices and higher order aberrations.6,52,53 Confocal microscopy performed 1 year after CXL showed good results with no substantial alteration in the endothelial cell count.54
However, compared to keratoconus eyes, the gain in BCVA is slow and usually not seen until 12 months after the procedure.55 This is because cross-linking results in strengthening mainly of the anterior part of stroma, which is already compromised due to the creation of flap in a LASIK patient.56
Various modifications of CXL to the original protocol have been tried to increase the efficacy in PLE patients:
  • Epithelium on CXL.4
  • Under flap CXL (ufCXL): early onset mild cases of PLE treated by lifting the LASIK flap and irradiating with 18 mW/cm2 UV light.57
  • Athens protocol: Consecutive sequential topography-guided partial transepithelial PRK and CXL.58,59
  • Combined PTK-PRK-CXL (Cretan protocol plus) has also been successfully used to stop the progress of PLE.60
Intracorneal Ring Segments (ICRS)
Various ICRS such as Intacs, Ferrara rings and Kera rings have been used successfully in the management of PLE (Figs. 8A to C).6163 These implants flatten the central portion of the cornea thereby reducing myopia. Its efficacy has been found to be directly proportional to the thickness of the segment, and inversely proportional to its diameter. The progression of PLE is often halted and a corneal transplant may no longer be required. The advantages are that it is reversible and tissue saving in nature.15
zoom view
Figs. 8A to C: Intracorneal ring segments used in the management of post-laser-assisted in situ keratomileusis ectasia. (A) Intacs; (B) Ferrara rings; (C) Kera rings.
The indications of ICRS are:
  • Patients with loss of more than or equal to 2 Snellen's lines of BCVA.
  • Grade 4 PLE.
Contraindications to ICRS implantation are:
  • Any previous ocular surgery.
  • Vernal keratoconjunctivitis.16
  • Viral keratitis.
  • Pregnancy/lactation period.
The complications seen with ICRS are:62
  • Intraoperative: Segment decentration, insufficient depth of channel, superficial dissection with perforation of Bowman's membrane
  • Postoperative: Extrusion of implant, neovascularization, infective keratitis, segment migration, melting of cornea
For PLE, implantation of a single segment in the ectatic portion is more effective in reducing the refractive error than implanting two segments.64
Combination of ICRS and CXL has been tried successfully for vision improvement as well as stabilization of ectasia.65
A new variety of ICRS known has Intacs SK (severe keratoconus) has been used in advanced cases of PLE with good results.66
Corneal transplant is used as a last resort in cases with intolerance to RGP lenses, and unacceptable BCVA, usually having contraindication to CXL or ICRS. PKP is the most commonly performed transplant of choice in ectasia patients. The visual prognosis in PLE cases is excellent, with graft survival rates reported to be 97% at 5 years and 92% at 10 years.8 Its complications include graft rejection, induced astigmatism, cataract, increased IOP, endophthalmitis, and retinal detachment.
Deep anterior lamellar keratoplasty (DALK) has recently been advocated for the surgical management of PLE.67 It has been performed in PLE cases using both Melles’ manual technique and Anwar's big-bubble technique.68,69 It effectively restores corneal regularity and improves BCVA. However, high-residual ametropia is often a common finding.
Newer surgical techniques, which have been tried for PLE, include:
  • Intralamellar keratoplasty (ILK): Schanzlin et al. demonstrated this technique in cases of severe PLE with sagging cones; a donor stromal lenticule is inserted into a stromal pocket of the recipient.70
  • Tuck-in lamellar keratoplasty: Similar to ILK; Jiang et al. used a donor lenticule obtained from patients undergoing SMILE (small incision lenticule extraction) procedure for this technique.62
  • Flap replacement surgery: Titiyal et al. described this novel procedure in which the LASIK flap is dissected and excised. A donor lenticule with Descemet's membrane and endothelium removed is taken, and tucked into an intrastromal pocket created in the recipient bed, and sutured.71
As described above, multiple etiological factors have been described for the development of PLE; however, PLE still often develops in patients who do not have any of these criteria. A review of the published literature incriminates three main culprits, which must be avoided:
  • Missed ectatic pathologies: These can be prevented by meticulous screening using corneal topography, especially the Belin/Ambrósio display 17on Pentacam® which can predict corneas prone to develop ectasia in the future (Figs. 9A and 9B).
  • Multiple enhancements: Ectatic disorders must be ruled out before retreatment is considered.
  • Thinned RSB: RSB must be routinely measured intraoperatively since thickness of flap has been known to vary considerably even in the hands of a single surgeon.
Screening protocols must be in place in every institute where LASIK is done, and it may be individualized based on the surgeon's experience. The Randleman's ectasia score is most commonly used; however, it has been criticized as not being able to detect high-risk patients among those having normal topography.72 Various other scoring systems have been developed;73 however, it is essential to develop a customized screening protocol based on the laser machine being used.
Some authors have reported combined procedures which may help to prevent the development of PLE:
  • Combined LASIK and CXL (LASIK Xtra): CXL serves as a prophylaxis against refractive regression and to prevent the development of PLE in high-risk patients. No associated decrease in visual acuity is seen. Refractive and keratometric outcomes have been shown to be comparable to or better than LASIK alone. No case of PLE has been reported in these patients.7478
The following laser refractive procedures have been shown to have lesser risk of development of PLE as compared to LASIK:
  • Femto-LASIK is more consistent and has more predictable flap size and depth of ablation, and it also causes limited reduction of corneal biomechanical integrity.35
  • SMILE is thought to preserve the anterior stromal collagen which has a bigger role in the maintenance of corneal integrity.79
  • Photorefractive keratectomy, ASA, and SBK cause lesser reduction in corneal tensile strength compared to LASIK.28
Post-LASIK ectasia has not emerged as the epidemic as was predicted by the critics in the early years of refractive surgery. However, even a single case can be problematic considering its medicolegal implications and the number of disability affected life years (DALYs) involved. Hence, every refractive surgeon must be aware of this important complication, and the screening protocols which have been developed for its prevention. It is also equally important to be able to detect its presence early, and provide appropriate management, since early treatment has been shown to have promising visual rehabilitative results. However, despite all screening protocols, ectasia has been seen to develop even in subjects with seemingly no risk factor. Hence, the Joint Consensus Committee of 2005 had recommended that PLE be considered a known risk factor of laser refractive procedures, which may develop despite the strictest screening protocols.18
zoom view
Figs. 9A and B: Corneal topography of a high-risk patient screened out for laser-assisted in situ keratomileusis. (A) Four maps refractive showing no obvious abnormality apart from high steep K (47.9 D); (B) Belin/Ambrósio display showing suspicious changes in anterior float, predictive of possible future ectasia development.
19The patient should be made aware of this entity before the procedure, and a meticulous follow-up of high-risk patients is essential.
  1. Kamiya K, Igarashi A, Hayashi K, et al. A multicenter retrospective survey of refractive surgery in 78,248 eyes. J Refract Surg. 2017;33(9):598–602.
  1. Karabela Y, Muftuoglu O, Gulkilik IG, et al. Intraoperative and early postoperative flap-related complications of laser in situ keratomileusis using two types of Moria microkeratomes. Int Ophthalmol. 2014;34(5):1107–14.
  1. Vinciguerra P, Camesasca F, Albè E, et al. Corneal collagen cross-linking for ectasia after excimer laser refractive surgery: 1-year results. J Refract Surg. 2010;26(7):486–97.
  1. Moscovici BK, Campos M. Intrastromal crosslinking in post-LASIK ectasia. Arq Bras Oftalmol. 2014;77(3):191–2.
  1. Seiler T, Koufala K, Richter G. Iatrogenic keratectasia after laser in situ keratomileusis. J Refract Surg. 1998;14(3):312–7.
  1. Tong JY, Viswanathan D, Hodge C, et al. Corneal collagen crosslinking for post-LASIK ectasia: an Australian study. Asia Pac J Ophthalmol. 2017;6(3):228–32.
  1. Pallikaris IG, Kymionis GD, Astyrakakis NI. Corneal ectasia induced by laser in situ keratomileusis. J Cataract Refract Surg. 2001;27(11):1796–802.
  1. Binder PS, Lindstrom RL, Stulting RD, et al. Keratoconus and corneal ectasia after LASIK. J Cataract Refract Surg. 2005;31(11):2035–8.
  1. Randleman JB, Woodward M, Lynn MJ, et al. Risk assessment for ectasia after corneal refractive surgery. Ophthalmology. 2008;115(1):37–50.
  1. Rao SN, Epstein RJ. Early onset keratectasia following laser in situ keratomileusis: case report and literature review. J Refract Surg. 2002;18(2):177–84.
  1. Said A, Hamade IH, Tabbara KF. Late onset corneal ectasia after LASIK surgery. Saudi J Ophthalmol. 2011;25(3):225–30.
  1. Gupta C, Tanaka TS, Elner VM, et al. Acute hydrops with corneal perforation in post-LASIK ectasia. Cornea. 2015;34(1):99–100.
  1. Cheung AY, Heidemann DG. Globe rupture of a post-LASIK keratectasia eye from blunt trauma. Cornea. 2016;35(12):1662–4.
  1. Condon PI. 2005 ESCRS Ridley Medal Lecture: will keratectasia be a major complication for LASIK in the long term? J Cataract Refract Surg. 2006;32(12):2124–32.
  1. Randleman JB, Russell B, Ward MA, et al. Risk factors and prognosis for corneal ectasia after LASIK. Ophthalmology. 2003;110(2):267–75.
  1. Padmanabhan P, Reddi SR, Sivakumar PD. Topographic, tomographic, and aberrometric characteristics of post-LASIK ectasia. Optom Vis Sci. 2016;93(11):1364–70.
  1. Duffey RJ, Leaming D. US trends in refractive surgery: 2004 ISRS/AAO survey. J Refract Surg. 2005;21(6):742–8.
  1. Kerautret J, Colin J, Touboul D, et al. Biomechanical characteristics of the ectatic cornea. J Cataract Refract Surg. 2008;34(3):510–3.
  1. Andreassen TT, Simonsen AH, Oxlund H. Biomechanical properties of keratoconus and normal corneas. Exp Eye Res. 1980;31(4):435–41.
  1. Barraquer JI. Queratomileusis y Queratofakia. Bogota: Instituto Barraquer de America. 1980;405–6.
  1. Amoils SP, Deist MB, Gous P, et al. Iatrogenic keratectasia after laser in situ keratomileusis for less than −4 to −7 diopters of myopia. J Cataract Refract Surg. 2000;26(7):967–77.20
  1. Condon PI, O'Keefe M, Binder PS. Long-term results of laser in situ keratomileusis for high myopia: risk for ectasia. J Cataract Refract Surg. 2007;33(4):583–90.
  1. Santhiago M, Smadja D, Gomes B, et al. Association between the percent tissue altered and post-laser in situ keratomileusis ectasia in eyes with normal preoperative topography. Am J Ophthalmol. 2014;158(1):87–95.
  1. Santhiago M, Smadja D, Wilson S, et al. Role of percent tissue altered on ectasia after LASIK in eyes with suspicious topography. J Refract Surg. 2015;31(4):258–65.
  1. Brenner LF, Alió JL, Vega-Estrada A, et al. Clinical grading of post-LASIK ectasia related to visual limitation and predictive factors for vision loss. J Cataract Refract Surg. 2012;38(10):1817–26.
  1. Huang X, He X, Tan X. [Research of corneal ectasia following laser in situ keratomileusis in rabbits]. Yan Ke Xue Bao. 2002;18(2):119–22.
  1. Tatar MG, Kantarci FA, Yildirim A, et al. Risk factors in post-LASIK corneal ectasia. J Ophthalmol. 2014;2014:204191.
  1. Dawson DG, Grossniklaus HE, McCarey BE, et al. Biomechanical and wound healing characteristics of corneas after excimer laser keratorefractive surgery: is there a difference between advanced surface ablation and sub-Bowman's keratomileusis? J Refract Surg. 2008;24(1):S90–6.
  1. Randleman JB. Post-laser in-situ keratomileusis ectasia: current understanding and future directions. Curr Opin Ophthalmol. 2006;17(4):406–12.
  1. Giri P, Azar DT. Risk profiles of ectasia after keratorefractive surgery. Curr Opin Ophthalmol. 2017;28(4):337–42.
  1. Padmanabhan P, Aiswaryah R, Abinaya PV. Post-LASIK keratectasia triggered by eye rubbing and treated with topography-guided ablation and collagen cross-linking—a case report. Cornea. 2012;31(5):575–80.
  1. Padmanabhan P, Radhakrishnan A, Natarajan R. Pregnancy-triggered iatrogenic (post-laser in situ keratomileusis) corneal ectasia—a case report. Cornea. 2010;29(5):569–72.
  1. Belin M, Ambrόsio R. The Belin/Ambrósio enhanced extasia display. [online] Available from
  1. Binder PS. Analysis of ectasia after laser in situ keratomileusis: risk factors. J Cataract Refract Surg. 2007;33(9):1530–8.
  1. Vahdati A, Seven I, Mysore N, et al. Computational biomechanical analysis of asymmetric ectasia risk in unilateral post-LASIK ectasia. J Refract Surg. 2016;32(12):811–20.
  1. Harissi-Dagher M, Frimmel SA, Melki S. High myopia as a risk factor for post-LASIK ectasia: a case report. Digit J Ophthalmol. 2009;15(1):9–13.
  1. Binder PS. Ectasia after laser in situ keratomileusis. J Cataract Refract Surg. 2003;29(12):2419–29.
  1. Santhiago MR, Giacomin NT, Smadja D, et al. Ectasia risk factors in refractive surgery. Clinical Ophthalmology. 2016;10:713–20.
  1. Dawson DG, Randleman JB, Grossniklaus HE, et al. Corneal ectasia after excimer laser keratorefractive surgery: histopathology, ultrastructure, and pathophysiology. Ophthalmology. 2008;115(12):2181–91.
  1. Ali Javadi M, Kanavi MR, Mahdavi M, et al. Comparison of keratocyte density between keratoconus, post-laser in situ keratomileusis keratectasia, and uncomplicated post-laser in situ keratomileusis cases. A confocal scan study. Cornea. 2009;28(7):774–9.21
  1. Akhtar S, Alkatan H, Kirat O, et al. Ultrastructural and three-dimensional study of post-LASIK ectasia cornea. Microsc Res Tech. 2014;77(1):91–8.
  1. Liu Y, Konstantopoulos A, Riau AK, et al. Repeatability and reproducibility of corneal biometric measurements using the visante omni and a rabbit experimental model of post-surgical corneal ectasia. Transl Vis Sci Technol. 2015;4(2):16.
  1. Maguen E, Maguen B, Regev L, et al. Immunohistochemical evaluation of two corneal buttons with post-LASIK keratectasia. Cornea. 2007;26(8):983–91.
  1. Meghpara B, Nakamura H, Macsai M, et al. Keratectasia after laser in situ keratomileusis: a histopathologic and immunohistochemical study. Arch Ophthalmol. 2008;126(12):1655–63.
  1. Pahuja NK, Shetty R, Deshmukh R, et al. In vivo confocal microscopy and tear cytokine analysis in post-LASIK ectasia. Br J Ophthalmol. 2017;101(12):1604–10.
  1. Elmohamady MN, Abdelghaffar W, Salem TI. Tear martix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 in post-LASIK ectasia. Int Ophthalmol. 2018.
  1. Guirao A. Theoretical elastic response of the cornea to refractive surgery: risk factors for keratectasia. J Refract Surg. 2005;21(2):176–85.
  1. Hiatt JA, Wachler BS, Grant C. Reversal of laser in situ keratomileusis induced ectasia with intraocular pressure reduction. J Cataract Refract Surg. 2005;31(8):1652–5.
  1. Kramer EG, Boshnick EL. Scleral lenses in the treatment of post-LASIK ectasia and superficial neovascularization of intrastromal corneal ring segments. Cont Lens Anterior Eye. 2015;38(4):298–303.
  1. Mahadevan R, Jagadeesh D, Rajan R, et al. Unique hard scleral lens post-LASIK ectasia fitting. Optom Vis Sci. 2014;91(4 Suppl 1):S30–3.
  1. Wollensak G, Spoerl E, Seiler T. Riboflavin/ultraviolet-a-induced collagen crosslinking for the treatment of keratoconus. Amer J Ophthalmol. 2003;135(5):620–7.
  1. Greenstein SA, Fry KL, Hersh PS. Corneal topography indices after corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results. J Cataract Refract Surg. 2011;37(7):1282–90.
  1. Poli M, Cornut PL, Balmitgere T, et al. Prospective study of corneal collagen cross-linking efficacy and tolerance in the treatment of keratoconus and corneal ectasia: 3-year results. Cornea. 2013;32(5):583–90.
  1. Kymionis GD, Diakonis VF, Kalyvianaki M, et al. One-year follow-up of corneal confocal microscopy after corneal cross-linking in patients with post laser in situ keratomileusis ectasia and keratoconus. Am J Ophthalmol. 2009;147(5):774–8.
  1. Hersh PS, Greenstein SA, Fry KL. Corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results. J Cataract Refract Surg. 2011;37(1):149–60.
  1. Wan Q, Wang D, Ye H, et al. A review and meta-analysis of corneal cross-linking for post-laser vision correction ectasia. J Curr Ophthalmol. 2017;29(3):145–53.
  1. Wallerstein A, Adiguzel E, Gauvin M, et al. Under-flap stromal bed CXL for early post-LASIK ectasia: a novel treatment technique. Clin Ophthalmol. 2017;11:1–8.
  1. Kanellopoulos AJ, Binder PS. Management of corneal ectasia after LASIK with combined, same-day, topography-guided partial transepithelial PRK and collagen cross-linking: the Athens protocol. J Refract Surg. 2011;27(5):323–31.
  1. Tamayo GE, Castell C, Vargas P, et al. High-resolution wavefront-guided surface ablation with corneal cross-linking in ectatic corneas: a pilot study. Clin Ophthalmol. 2017;11:1777–83.
  1. Zhu W, Han Y, Cui C, et al. Corneal collagen crosslinking combined with phototherapeutic keratectomy and photorefractive keratectomy for corneal ectasia after laser in situ keratomileusis. Ophthalmic Res. 2018;59(3):135–41.22
  1. Carrasquillo KG, Rand J, Talamo JH. Intacs for keratoconus and post-LASIK ectasia: mechanical versus femtosecond laser-assisted channel creation. Cornea. 2007;26(8):956–62.
  1. Jiang Y, Li Y, Yang S, et al. Tuck-in Lamellar keratoplasty with a lenticule obtained by small incision lenticule extraction for treatment of Post-LASIK ectasia. Sci Rep. 2017;7(1):17806.
  1. Tunc Z, Helvacioglu F, Sencan S. Evaluation of intrastromal corneal ring segments for treatment of post-LASIK ectasia patients with a mechanical implantation technique. Indian J Ophthalmol. 2011;59(6):437–43.
  1. Hashemi H, Gholaminejad A, Amanzadeh K, et al. Single-segment and double-segment Intacs for post-LASIK ectasia. Acta Med Iran. 2014;52(9):681–6.
  1. Yildirim A, Uslu H, Kara N, et al. Same-day intrastromal corneal ring segment and collagen cross-linking for ectasia after laser in situ keratomileusis: long-term results. Amer J Ophthalmol. 2014;157(5):1070–6.
  1. Kymionis GD, Bouzoukis DI, Portaliou DM, et al. New INTACS SK implantation in patients with post-laser in situ keratomileusis corneal ectasia. Cornea. 2010;29(2):214–6.
  1. McAllum PJ, Segev F, Herzig S, et al. Deep anterior lamellar keratoplasty for post-LASIK ectasia. Cornea. 2007;26(4):507–11.
  1. Salouti R, Nowroozzadeh MH, Makateb P, et al. Deep anterior lamellar keratoplasty for keratectasia after laser in situ keratomileusis. J Cataract Refract Surg. 2014;40(12):2011–8.
  1. Javadi MA, Feizi S. Deep anterior lamellar keratoplasty using the big-bubble technique for keratectasia after laser in situ keratomileusis. J Cataract Refract Surg. 2010;36(7):1156–60.
  1. Tan BU, Purcell TL, Torres LF, et al. New surgical approaches to the management of keratoconus and post-LASIK ectasia. Trans Am Ophthalmol Soc. 2006;104:212–20.
  1. Titiyal JS, Agarwal T, Jhanji V, et al. Flap replacement surgery for management of post-LASIK ectasia. Br J Ophthalmol. 2010;94(12):1690–2.
  1. Binder PS, Trattler WB. Evaluation of a risk factor scoring system for corneal ectasia after LASIK in eyes with normal topography. J Refract Surg. 2010;26(4):241–50.
  1. Miraftab M, Fotouhi A, Hashemi H, et al. A modified risk assessment scoring system for post laser in situ keratomileusis ectasia in topographically normal patients. J Ophthalmic Vis Res. 2014;9(4):434–8.
  1. Tomita M, Yoshida Y, Yamamoto Y, et al. In vivo confocal laser microscopy of morphologic changes after simultaneous LASIK and accelerated collagen crosslinking for myopia: one-year results. J Cataract Refract Surg. 2014;40(6):981–90.
  1. Nguyen MK, Chuck RS. Corneal collagen cross-linking in the stabilization of PRK, LASIK, thermal keratoplasty, and orthokeratology. Curr Opin Ophthalmol. 2013;24(4):291–5.
  1. Aslanides IM, Mukherjee AN. Adjuvant corneal crosslinking to prevent hyperopic LASIK regression. Clin Ophthalmol. 2013;7:637–41.
  1. Kanellopoulos AJ, Asimellis G. Epithelial remodeling after femtosecond laser-assisted high myopic LASIK: comparison of stand-alone with LASIK combined with prophylactic high-fluence cross-linking. Cornea. 2014;33(5):463–9.
  1. Kymionis GD, Grentzelos MA, Portaliou DM, et al. Corneal collagen cross-linking (CXL) combined with refractive procedures for the treatment of corneal ectatic disorders: CXL plus. J Refract Surg. 2014;30(8):566–76.
  1. Moshirfar M, Albarracin JC, Desautels JD, et al. Ectasia following small-incision lenticule extraction (SMILE): a review of the literature. Clin Ophthalmol. 2017:11:1683-8.