Corneal Tomography in Clinical Practice (Pentacam System): Basics and Clinical Interpretation Sinjab Mazen M
INDEX
ABCDEFGHIKLMNOPQRSTUVWZ
Page numbers followed by f refer to figure, and t refer to table
A
Aberrations
classification of 105
measurement of 105
root mean square measurement of 105f
third-order 118
Zernike description of 111t
Aberrometers 106
Aberrometry
ingoing
feedback 106
reflective 106
Ablation zone 195
Abnormal anterior difference map 197f
Accommodation 106
Achromatic axis 3
Airy pattern 107f
Alio-Shabayek
classification 181t
modification 180
Amsler-Krumeich
classification 180, 180t, 181
standards 181t
Angle 31
alpha 4
kappa 3, 24f, 222
estimation of 4f, 5f
lambda 4
Anisometropia 94, 94f
Anterior chamber depth 16, 222
Anterior corneal surface 32, 158f
elevation maps of 45f
radius of curvature of 5
Anterior elevation map 154f, 189, 191, 193, 195f, 198f, 199f
Anterior refractive power map 35f
Anterior sagittal curvature map 33, 17f
patterns of 39f
Anterior sagittal map 35f, 206
Anterior segment optical coherence tomographers-based tomography 12f
Anterior tangential map 189, 190f, 195f, 198f, 206
Apex position 17
Aqueous humor 30
Arcuate incision 220f
Aspheric lenses 169
Asphericity 127
patterns of 76
Astigmatic aberration 117
Astigmatic disparity 99, 99f, 146
management of 100
probabilities of 100t
types of 100
Astigmatic lower-order aberration 83, 117f
Astigmatism 83, 99, 101
axis of 16
classification of 83
compound 84
hypermetropic 84
myopic 84
hyperopic 4
mixed 4, 84
irregular 85
nonperiodic irregular 85
oblique 38, 39f, 53f, 85
origin of 83
periodic irregular 85, 85f
secondary 119
simple 84
tomographic 24, 26f, 99, 100, 101
treatment of 219
types of 83
Asymmetric bowtie
inferior steep 40f
superior steep 40f
B
Back vertex distance 95
Belin ABCD grading system 180
Belin ABCD keratoconus staging 182f, 182t, 183f
comparative display of 183f
Belin/Ambrósio display 178f, 196f, 197f
Belin/Ambrósio ectasia display 54, 56f, 58f, 189
abnormal 59f
false-negative 62f
false-positive 63f
normal 57f
Belin/Ambrósio enhanced ectasia 54, 54f
clinical application of 60
display, principle of 55f
Bell and Globus patterns, high-risk 165f
Bell pattern 64, 65f
Best-corrected visual acuity 88
Best-fit-sphere 19, 47, 48, 75
reference surface 49f, 50f, 51f, 54, 162f
Best-fit-Toric ellipsoid reference surface 50f, 163f
Bowman's layer 89
C
Capture, validating quality of 22
Cataract 99
incision, characteristics of 219
surgery 148, 218
Central corneal thickness 6, 30, 143, 180
Central flat island 88f
Central island 51, 51f, 87, 88f
Chamber volume 31
Clown face 43f
Color map appearance 16
Coma 118, 120f
Cone location and magnitude index 185
Contact lenses 143
use of 99
Conventional camera 11f
Cornea 6f, 9f, 21, 173, 177
abnormal 173t, 177
back, posterior surface 30
front, anterior surface 29
guttata 64, 219
irregular 61f
meridional power of 96f, 97f
normal high-astigmatic 209
normal low-astigmatic 210, 210f, 211f
oblate 76, 130f
parabolic 135f
positive-prolate 130f
volume 31
Corneal and ocular spherical aberration, range of 133f
Corneal apex power 185
Corneal asphericity 6, 75, 76, 127, 139
effect of 137, 139
principle of 75f
Corneal astigmatism 40f, 47f, 51f, 161, 220, 220f, 221f
total 25f
Corneal asymmetry 76, 77, 79
Corneal changes with age 109
Corneal crosslinking 64, 184, 218
Corneal curvature map, patterns of 37
Corneal dimensions 5
Corneal epithelium, effect of 6f
Corneal geometry 3, 5, 8
Corneal graft 148
after removal of 91f
before suture removal 90f
Corneal incisions 220f
Corneal irregularities 218
Corneal landmarks 30f
Corneal levels 106
Corneal opacities 99, 148
Corneal optics 3
Corneal parameters 29, 29f
Corneal pathologies 148
Corneal periphery 18f, 195
Corneal power 6
maps 32
measurement 32, 32t
Corneal refraction 81
Corneal scar 66f–69f
tomographic features of 89
Corneal shape 6, 75, 127
Corneal spherical aberration 127, 128
after hyperopic ablation 134f
after myopic ablation 133f
Corneal surgeries 148, 219
previous 99, 148
Corneal thickness 6, 32, 158f, 186
map 20f, 64f, 164f, 165f, 206
overlay for 22f
spatial profile 64, 66, 70f, 219
thinnest 6, 158, 186, 187f
Corneal tomography 94, 106, 171, 218
systematic interpretation of 141
Corneal topography 94
Corneal topometry 75
anterior 190, 191f, 195f, 199f
Corneal toricity 75
Corneal wavefront, fourier analysis of 123f, 124
Corneal zones 6
Corrected distance visual acuity 180
Crab claw 43f
Crystalline lens changes with age 109
Curvature
anterior radius of 187
color scale for 17f
map 16f, 17, 38, 75, 76, 144
anterior 144f
posterior radius of 187
radius of 5, 14
Cycloplegic refraction 94
D
Disciform pattern 64f, 191f
Discrete pattern 201, 202f
Display 55
Droplet pattern 65, 66f
Dry eye 92f, 149f, 150f
disease 146, 218
E
Ectasia 60, 173, 189, 194f
after laser vision correction 176f
Ectatic corneal diseases 31, 48, 54, 78f, 79f, 95, 110, 143, 173, 171, 173t, 180, 184, 185t, 189, 206, 218
diagnosis of 64
early 110
evaluation of 21
grading systems of 180
tomographic characteristics of 173
Efficient optical zone 91, 195
Elevation maps 17f, 19, 45, 45f, 46f, 50f, 53f, 75, 76, 79, 145, 158, 186, 207, 210
abnormal 49f, 50f
color scale of 45f
high-risk 162f, 163f
overlay for 19f
patterns of 49
principle of 45, 45f
Emmetropia 139
Enantiomorphism 152, 152f–156f
Epithelium, remodeling characteristic of 7f
Equivalent K-reading power map 35
Excess tear 151f
film 146
Eye, optical system of 3f
F
Focus, depth of 127, 132, 134f, 135f, 139f
Forme-Fruste keratoconus 173, 178f, 205
Four-composite
refractive map 67f, 93f, 98f, 147f, 156f
selective map 68, 194f, 198f, 200f
Fourier analysis 109, 123, 123f, 124, 126f
Fourth order aberrations 118
Foveola 3
Fuchs’ endothelial dystrophy 64, 219
G
Geometric tomography 75
Globus pattern 65, 66f
H
Height asymmetry, index of 185
Higher-order aberrations 48, 99, 105, 111, 114f, 117, 118f
Holladay report 22f, 24f, 205, 205f, 207, 208f, 210f–212f, 214, 214f, 215f
specific settings for 20
Horizontal displacement pattern 64, 65f
Horizontal white-to-white diameter 222
Hot spot pattern 144f, 200
Human eye, optical system of 3
Hybrid devices 13
Hyperopia 4, 139
Hyperprolate 128
cornea 128f, 131f, 135f
curvature pattern 77f, 78f
I
Incision
clock-hour extension of 221f
length 220f
location 220f
orientation 221f
planes 221f
shape 220f
Inferior meniscus pattern 201f
Inferior steep 40f
Intereye corneal asymmetry score 155t, 162, 167t
Internal aberration compensation 109
Intraocular lens 12, 205
selection 110
Intraocular pressure 31
Irregular astigmatism 85, 99, 223
evaluation of 90
objective evaluation of 94
subjective evaluation of 91
suspicion of 91
treatment of 219
types 112
K
Keratoconic cornea 183f
Keratoconic eye 145f
Keratoconus 98f, 123f, 143, 173, 174f, 179f, 185, 211, 212f
Alio-Shabayek classification of 181t
Amsler-Krumeich classification of 180t
classification of 180, 181t
pellucid-like 173, 175f, 213f, 214f
peripheral 10
posterior 177, 179f
progression 187f
Keratoglobus 173, 176f
Keratometric dioptric power 95
Keratometry 8, 87
Keratoplasty, penetrating 87
Keratotomy, astigmatic 148, 221
K-readings after corneal crosslinking, changes of 188f
L
Lamellar ablation 87
Lamellar keratoplasty 89
Large angle
kappa 24f, 99, 63f, 146, 156f
lambda 146
Laser vision correction 64, 88, 99, 148, 173, 219
Lazy S-shape pattern 72f
Left eye
corneal shape of 5f
four-composite refractive map of 156f
Lens
subluxation 99
thickness 31
Lenticular astigmatism 99
Light-emitting diodes 10
Limbal relaxing incisions 148, 221
Limbal zone 6
Lower-order aberrations 105, 115
Low-risk elevation maps 162f, 163f
Low-risk irregular curvature map 168
M
Macro-irregular pattern 87
Maps 206
Maximum K-reading 184, 187f
Mean anterior keratometry 167
Mean posterior keratometry 167
Mercedes-Benz image 119f
Meridians 5
Micro-irregular pattern 87
Mild peripheral extrapolation 19f
Minimum radius position front 17
Modulation transfer function 107, 109f
principle of 108f
Myopia 139
N
Negative prolate 128
corneal shape 128f
Negative spherical aberration 131f
Neural adaptation 135
range 169
Nodular point 3
Nonoptimum spectacle-corrected distance visual acuity 91
Nontoxic spherical aberration 138f
Normal cornea 6f, 182f
Fourier analysis of 126f
Normal elevation maps 49f, 50f
O
Objective corneal
dioptric power 95
refraction 95
Objective dioptric power, meridional power of 96f–98f
Objective spherocylindric dioptric power 95
Oblate curvature pattern 77f
Oblate elevation pattern 78f
Oblique curvature asymmetry 78f
Ocular pathologies 106
Ocular spherical aberration 128, 135
Ocular surface disease 10, 12, 218
Ocular surgeries, previous 106
Optical axis 3, 38
Optical coherence tomographers 8
Optical transfer function 108
Optical zones 190f, 195f
P
Pachy apex 30
Pachymetric data 54, 55
Pachymetric progression index 67, 70f
Pachymetry 17f
map 64, 69f, 167f, 195f, 201, 211
low-risk relative 167f
relative 160, 189, 191, 191f, 193, 199f, 207, 209, 213
profiles 160, 165f
thinnest 167
Para ectasia 173, 177f, 178f
Parabola 127
Paracentral zone 6
Parameters 46
Pellucid marginal degeneration 10, 64, 173, 175f, 214f, 215f
Peripheral corneal scar 92f
Peripheral scars 10
Peripheral zone 6
Photokeratoscopy 8
Pinhole test 91
Piston 116f
Placido cone 9
Placido disk 8f
Placido mires, reflection of 9f
Point spread function 107
Postastigmatic ablation pattern 198f, 199f
Postcorneal-graft pattern 199, 200f, 201f
Posterior corneal surface 32
radius of curvature of 5
Posterior elevation map 21f, 50f, 89, 154f
Posterior tangential curvature map 33
Posthyperopic ablation pattern 194f–197f
Posthyperopic astigmatic ablation pattern 199f
Posthyperopic laser ablations 7f
Postkeratoplasty 206
Postkeratorefractive surgeries 206
Postmydriatic test 94
Postmyopic ablation pattern 190f, 191f, 198f
Postoperative corneal
flattening 223
steepening 222
Power distribution display 98f
Practical subjective
optical coherence tomographers selection 169, 170
scoring system 30, 157, 157t, 178
Premium lenses 169
Previous corneal refractive surgeries, diagnosis of 64
Progression, parameters of 184
Pterygium, bilateral 93f
Pupil 3
center 30
coordinates 146
intereye symmetric coordinates of 24f
size 222
Pupillary axis 3
Pupillary levels 106
Purkinje images 3
Pyramid display 113f
Q
Quality specification 22, 145
Quick slope 71f
Q-value and corneal asphericity 128
R
Rabinowitz method 41f
Radial keratotomy 148
Reference surface 45
parameters of 47f
Reflective aberrometry 106
Reflex, irregular 91
Refractive effect 32
Refractive errors 117
Refractive index 5, 30, 32
Refractive power map 33
Refractive surgery
candidate, right eye of 152f
laser-based 162, 168t
Regular astigmatism 83, 84f, 124, 125f
treatment of 219
Retina 3
Retinal level 107
Retinoscopy 91
Right eye
corneal geometry of 5f
four-composite refractive map of 156f
superior view of 3f
Rigid gas permeable 91
contact lenses 143
Root mean square 88, 105f, 106
S
Sagittal curvature map 42, 161f
Sagittal map 209–211
Scheimpflug camera 11f
principle of 10f
Scheimpflug image 99f
Scheimpflug-based technology, principle of 11f
Scleral incisions 220f
Secondary astigmatism 119
higher-order aberration 122f
Segmental elevation asymmetry 80f
Sight, principle line of 3
Sim-K measurement 8f
Skewed radial axis index 42, 161f, 221
high-risk 160f
Slit-scanning technology, principle of 10f
Soft contact lens 93f, 143, 144f
Spatial thickness profile 145
Spheric lenses 169
Spherical aberration 32, 35f, 121f, 128, 129f, 131f, 132, 132f, 134f, 136f, 139f
classification of 136f
positive 130f
range of 132f
types of 129f
Spherical component 124, 124f
Spherical cornea 76, 130f
depth of focus in 134f
Spherical curvature pattern 77f
Spherical elevation pattern 77f
S-shape pattern 71f
Standard deviation 49
Steep and flat semimeridians, significant segmentation of 38f
Sturm interval 84f
Subjective refraction, prediction of 109
Surface ablation 87
T
Tangential map 209–211
Tear film disturbance 99, 146
Tetrafoil 119, 122f
Thickness map 74f, 145, 155
abnormal relative 74f
overlay 19
Thin cornea, normal 174f
Tolerable spherical aberration 137f
Tomographers
elevation-based 10, 13
optical coherence tomographers-based 11
types of 11
Tomography 8, 11, 12t
elevation-based 12
optical coherence tomographers-based 12
skillful interpretation of 157
Tongue-like extension pattern 80f
Topographers 8, 13
Topography 8, 11, 12, 12t
Topometric display 160f
Topometric indices 185
Topometry display 159f
Total corneal refractive
power 25f, 95, 99
map 37, 37f
principle 37f
Toxic spherical aberration 138f
Transitional zone 191, 195
Trefoil 118, 119f
True corneal astigmatism 219
True net power map 34
True refractive index 32
U
Uncorrected distance visual acuity 143
V
Vertex keratoscope normal 3
Vertical asymmetry, index of 185
Vertical displacement pattern 64, 65f
Videokeratoscope 3, 37, 38
Videokeratoscopy, computerized 9
Visual acuity and manifest refraction 186
Visual axis 3, 38
Visual function and spherical aberration 132
Vortex pattern 44f
W
Wavefront analysis 94
and measurements, basics of 105
principles of 105
Wavefront principle 105f
Wavefront science 103
Wavefront technology, clinical application of 109
Z
Zernike analysis 111, 168f
Zernike coefficient 109, 111, 112
Zernike polynomials 111, 112, 115
display, standard setting of 113f
Zernike pyramid 106
×
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CORNEAL TOMOGRAPHY IN CLINICAL PRACTICE (PENTACAM SYSTEM): Basics and Clinical Interpretation
NOTIFICATION
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CORNEAL TOMOGRAPHY IN CLINICAL PRACTICE (PENTACAM SYSTEM): Basics and Clinical Interpretation
Fourth Edition
Mazen M Sinjab MD MSc ABOphth PhD FRCOphth (Hons) CertLRS (London) Professor of Ophthalmology, Damascus University, Syria Visiting Professor, Hassan II University, Casablanca, Morocco Consultant Ophthalmic Surgeon Phaco-Refractive Surgeon Dr Mazen Sinjab Eye Clinic, Dubai, UAE Al Zahra Eye Center, Damascus, Syria
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Corneal Tomography in Clinical Practice (Pentacam System): Basics and Clinical Interpretation
First Edition: 2009
Second Edition: 2012
Third Edition: 2019
Fourth Edition: 2021
9781787791619
Printed at
My dear Father Mohamad (may God rest his soul),
who implanted in my soul the love of excellence
I will mention his name with my name all my life
My Mother Almasah (may God rest her soul),
who implanted in my heart the love of the poor and helping others
My Wife Ruba (may God save her),
For the unwavering support that was critical for all my success
Mazen Mohamad Sinjab
Man is born and has been granted “The Life”
To live is an only one chance that cannot be repeated
We have been created without our choice,
and we are going to die without our choice as well,
but to make our life is our choice
Success does not need to be created, it just needs to be made
Making success needs five tools, sincerity, honest, humility, persistence and patience
But, to deliver success to others, an additional tool is essential; it is loving others
“Make your success and deliver it to others; life is very short”
Mazen Mohamad Sinjab
Preface to the Fourth Edition
Since launching the 3rd edition, new concepts and applications of corneal tomography have risen. That made it necessary to write the 4th edition to stay up-to-date and allow the readers to catch up with the latest technology.
Why this edition? Because it helps better understanding of concepts and adds new applications of topography, tomography, and aberrometry in refractive surgery, cataract surgery, and keratoconus management.
This edition has two new chapters. It is divided into seven sections and 26 chapters, discussing in detail the basics and principles, guidelines of screening and validating the data, maps and profiles, wavefront analysis, factors of false findings, ectatic corneal diseases, and much more.
As always committed to simplifying the information and consolidating the concepts in a systematic step-by-step method, I keep on creating new methods to present the best for my readers.
Mazen M Sinjab
Preface to the First Edition
Taking the right decision in laser refractive surgery depends to a great extent on good reading of corneal topography and its clinical interpretation. This is very important for having the aimed results and avoiding postoperative complications.
The data in this book were obtained and gathered from the user manual of the Pentacam, international conferences, refractive journals, personal contacts with many refractive professors and of course self-experience.
The strategy in compiling this little book is combining excellence in pictorial quality with a concise but ordered text.
I have aimed the book at all those who need some initial assistance in reading and clinical interpretation of corneal topography. As the ophthalmology editor, I take full responsibility for any error and look forward to being further educated.
Mazen M Sinjab
Acknowledgments
I would like to acknowledge my wife Ruba and my daughter Reem for the kind assistance in designing the cover of this book.
Abbreviations AB
Asymmetric bowtie
AB/IS
Asymmetric bowtie inferior steep
AB/Srax
Asymmetric bowtie with skewed radial axis index
AB/SS
Asymmetric bowtie superior steep
AC
Anterior chamber
ACA
Anterior chamber angle
ACD
Anterior chamber depth
ACV
Anterior chamber volume
AK
Astigmatic keratotomy
AS-OCT
Anterior segment-optical coherence tomography
ATR
Against-the-rule
AZ
Ablation zone
BAD
Belin/Ambrósio Ectasia Display
BFS
Best fit sphere
BFTE
Best-fit-toric ellipsoid
BVD
Back vertex distance
CAD
Central ablation depth
CCT
Central corneal thickness
CDVA
Corrected distance visual acuity
CI
Confidence interval
CL
Contact lens
CLE
Clear lens extraction
CLVC
Customized laser vision correction
CP
Corneal periphery
CR
Cycloplegic refraction
CTSP
Corneal thickness spatial profile
CXL
Corneal crosslinking
D
Diopter
DED
Dry eye disease
DOF
Depth of focus
EBMD
Epithelial basement membrane dystrophy
ECDs
Ectatic corneal diseases
EDOF
Extended depth of focus
EKR
Equivalent K-reading
ELP
Effective lens position
EME
Entities misdiagnosed as ectasia
EOZ
Efficient optical zone
EP
Entrance pupil
Epi-LASIK
Epipolis laser in situ keratomileusis
Femto-LASIK
Femtosecond laser in situ keratomileusis
FFKC
Forme fruste keratoconus
FT
Flap thickness
HOAs
Higher-order aberrations
HSTS
Horizontal sulcus-to-sulcus
HWTW
Horizontal white-to-white
I
Inferior
ICRs
Intracorneal rings
IOL
Intraocular lens
IS
Inferior steep
K1
Flat K-reading
K2
Steep K-reading
KC
Keratoconus
KCS
Keratoconus suspect
KG
Keratoglobus
Km
Mean K-reading
Kmax
Maximum K-reading
Kref
Reference K-reading
LASEK
Laser subepithelial keratomileusis
LASIK
Laser in situ keratomileusis
LKP
Lamellar keratoplasty
LOAs
Lower-order aberrations
LOS
Line of sight
LRIs
Limbal relaxing incisions
LVC
Laser vision correction
MA
Manifest astigmatism
MTF
Modulation transfer function
NAR
Neural adaptation range
OA
Optical axis
OD
Right eye
ODP
Objective spherocylindric dioptric power
ODP-t
Translated objective spherocylindric dioptric power
OS
Left eye
OSD
Ocular surface disease
OTF
Optical transfer function
OZ
Optical zone
PA
Pupillary axis
PHT
Pin hole test
PIOL
Phakic intraocular lens
PKP
Penetrating keratoplasty
PLK
Pellucid-like keratoconus
PMD
Pellucid marginal degeneration
PMT
Postmydriatic test
PPI
Pachymetric progression index
PRK
Photorefractive keratectomy
PS3
The Practical Subjective Scoring System
PSF
Point spread function
PSIS
The Practical Subjective IOL Selection
PTA
Percent of tissue altered
PTF
Phase transfer function
PTI
Percentage thickness increase
PVA
Potential visual acuity
Qs
Quality specifications
RGP
Rigid gas permeable
RI
Refractive index
RK
Radial keratotomy
RLE
Refractive lens exchange
RMS
Root mean square
RS
Reference surface
S
Superior
SA
Spherical aberration
SB
Symmetric bowtie
SB/SRAX
Symmetric bowtie with skewed radial axis index
SBK
Sub-Bowman keratomileusis
SD
Standard deviation
SE
Spherical equivalent
SIA
Surgically induced astigmatism
Sim K
Simulated keratometry
SMILE
Small incision lenticule extraction
SR
Strehl ratio
SRAX
Skewed radial axis index
SS
Superior steep
TA
Tomographic astigmatism
TCRP
Total corneal refractive power
TCT
Thinnest corneal thickness
TL
Thinnest location
TNP
True net power
TR
Total refraction
TransPRK
Transepithelial photorefractive keratectomy
TZ
Treated zone
UDVA
Uncorrected distance visual acuity
VA
Visual axis
VK
Vertex keratoscope
WFG
Wavefront-guided
WFO
Wavefront-optimized
WTR
With-the-rule
ZC
Zernike coefficient