OCULUS Pentacam User manual

Interpretation Guide Pentacam®/ Pentacam®HR
INTERPRETATION GUIDE
3rd edition
Pentacam®
Pentacam® HR
OCULUS
WWW.OCULUS.DE
64/0915/EN/LA P/SD/004/EN
OCULUS Optikgeräte GmbH
Postfach •35549 Wetzlar •GERMANY
Tel. [phone] •Fax [phone]
E-Mail: [email protected] •www.oculus.de
• OCULUS USA, [email protected]
• OCULUS Asia, [email protected]
• OCULUS Czechia, [email protected]
• OCULUS Iberia, [email protected]
• OCULUS Poland, [email protected]
• OCULUS Slovakia, of[email protected]
• OCULUS Turkey, [e-mail]

Foreword
We thank you for the trust you have put in us by purchasing this OCULUS instrument. In
doing so you have chosen a modern, sophisticated product which was manufactured and
tested according to strict quality standards.
Our company has been doing business for over 120 years. Today OCULUS is a medium-
sized company focused entirely on developing and manufacturing advanced and innovative
instruments for examinations and surgery on the eye to help ophthalmologists, optometrists
and opticians in their routine work.
The Pentacam® is based on the Scheimpug principle, which generates precise and sharp
images of the anterior eye segment. This instrument takes extremely accurate measurements
and is easy to use.
If you have questions or desire further informations on this product, please turn to your
OCULUS representative or directly to OCULUS.
We will be glad to help you.
OCULUS Optikgeräte GmbH
OCULUS has been certified according to DIN EN ISO 13485 and therefore sets high quality
standards in the development, production, quality assurance and servicing of its entire
product range.
Note
OCULUS Optikgeräte GmbH wishes to emphasize that the user bears full responsibility
for the correctness of data measured, calculated or displayed using the Pentacam®. The
manufacturer will not accept claims based on erroneous data or misinterpretation. This
Interpretation Guide can no more than assist in the interpretation of examination data
generated by the Pentacam®.
In making a diagnosis physicians should not neglect to consider other medical information
which may be obtainable through other methods such as slit lamp examination or ultrasound
biomicroscopy, judiciously weighing the signicance of each.
This Interpretation Guide should be seen as a complement to the User Guide and Instruction
Manual. The current version of these documents and the Interpretation Guide are on every
Pentacam® Software USB drive and should be read by all users prior to use.

1
Table of contents
1 Introduction....................................................................................................................................................5
2 Description of the unit and general remarks..........................................................................................5
3 Differences between the various topography maps of Pentacam®.............................................6-11
3.1 Calculation of corneal power..........................................................................................................................6
3.2 Sagittal power map (also called axial power map)...................................................................................7
3.3 Refractive power map.......................................................................................................................................8
3.4 True Net Power....................................................................................................................................................9
3.5 Equivalent Keratometer Readings power map.........................................................................................10
3.6 Total Cornea Refractive Power map............................................................................................................11
4 Recommended settings and color maps, displays and values....................................................12-14
4.1 Recommended settings...................................................................................................................................12
4.2 Recommended color maps, displays and values......................................................................................13
4.2.1 Screening for corneal refractive surgery.......................................................................................13
4.2.2 Pre-op screening for iris fixated phakic IOL implantation.......................................................13
4.2.3 Glaucoma screening............................................................................................................................14
4.2.4 Cataract surgery and IOL calculation for virgin and post refractive corneas....................14
5 Differences between Placido and elevation-derived curvature maps
by Prof. Michael W. Belin....................................................................................................................15-19
5.1 Keratoconus in OD and OS?..........................................................................................................................15
5.2 Form fruste keratoconus?..............................................................................................................................18
6 Fast Screening Report as a first step in examining a patient and evaluating
one’s findings by Ina Conrad-Hengerer, MD.................................................................................20-27
6.1 Case 1: Unilateral high astigmatism with suspicion of bilateral keratoconus...............................20
6.2 Case 2: Fuchs’ dystrophy with DMEK cataract surgery – progress evaluation...............................23
6.3 Case 3: Corneal injury sustained from an eye drop bottle after cataract surgery.........................26
7 Refractive Power Distribution display by Ina Conrad-Hengerer, MD.......................................28-30
7.1 Visual acuity impairment during nighttime driving with distance spectacles –
nocturnal myopia?...........................................................................................................................................28
8 Corneal ectasia.....................................................................................................................................31-35
8.1 Case 1: Ectasia after radial keratotomy by Prof. Renato Ambrósio Jr .............................................31
8.2 Case 2: Ectasia after LASIK? by Prof. Michael W. Belin.........................................................................33
9 Glaucoma...............................................................................................................................................36-46
9.1 Case 1: General screening by Tobias H. Neuhann, MD..........................................................................36
9.2 Case 2: YAG laser iridectomy by Eduardo Viteri, MD.............................................................................37
9.3 Screening for narrow angles by Dilraj S. Grewal, MD...........................................................................39
9.3.1 Case 1.....................................................................................................................................................39
9.3.2 Case 2.....................................................................................................................................................42
9.4 Evaluating the anterior segment in phacomorphic glaucoma by Dilraj S. Grewal, MD..................45
Table of contents

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10 Screening for refractive surgery by Prof. Michael W. Belin................................................47-63
10.1 Screening parameters, 4 Maps Refractive display......................................................................47
10.1.1 Suggested installation settings...........................................................................................47
10.1.2 Proposed screening parameters...........................................................................................48
10.1.3 Strategy on how to go through the exams......................................................................49
10.2 Normal, astigmatic cornea................................................................................................................49
10.3 Astigmatism on the posterior cornea.............................................................................................52
10.4 Spherical cornea...................................................................................................................................53
10.5 Thin spherical cornea..........................................................................................................................54
10.6 Thin cornea............................................................................................................................................55
10.7 Borderline case of keratoconus........................................................................................................56
10.8 Displaced apex...................................................................................................................................... 57
10.9 Pellucid marginal degeneration.......................................................................................................58
10.10 Asymmetric keratoconus....................................................................................................................59
10.11 Keratoconus with false negative findings on curvature map..................................................61
10.12 Keratoconus greater in OD than OS................................................................................................62
10.13 Classic keratoconus.............................................................................................................................63
11 Corneal Thickness Spatial Profile by Prof. Renato Ambrósio Jr .......................................64-79
11.1 Screening for ectasia by Prof. Renato Ambrósio Jr, Marcela Q. Salomão, MD...................67
11.2 Case 1: Fuchs’ dystrophy by Prof. Renato Ambrósio Jr, Marcela Q. Salomão, MD............72
11.3 Case 2: Ocular hypertension by Prof. Renato Ambrósio Jr,
Marcela Q. Salomão, MD...................................................................................................................74
11.4 Case 3: Early Fuchs’ dystrophy with glaucoma by Prof. Renato Ambrósio Jr,
Marcela Q. Salomão, MD...................................................................................................................76
11.5 Screening parameters by Prof. Renato Ambrósio Jr ..................................................................79
12 Belin/Ambrósio Enhanced Ectasia Display.............................................................................80-102
12.1 Why elevation is displayed by Prof. Michael W. Belin...............................................................80
12.2 Simplifying preoperative keratoconus screening by Prof. Michael W. Belin,
Prof. Renato Ambrósio Jr, Andreas Steinmüller, MSc................................................................88
12.3 Interpretation of the Belin/Ambrósio Enhanced Ectasia Display............................................94
12.4 Pachymetry evaluation........................................................................................................................96
12.5 Ectasia susceptibility revealed by the Belin/Ambrósio Enhanced Ectasia Display.............96
12.6 Early ectasia with asymmetric keratoconus by Prof. Renato Ambrósio Jr,
Fernando Faria-Correia, MD, Allan Luz, MD...............................................................................100
13 Locating the cone by Prof. Michael W. Belin..............................................................................102
14 The corneal densitometry screen, Sorcha S. Ní Dhubhghaill, MB, PhD,
Jos J. Rozema, MSc, PhD.........................................................................................................103-107
14.1 Keratic precipitates............................................................................................................................104
14.2 Position and depth of INTACS® rings............................................................................................106
14.3 DSAEK with specks at the interface..............................................................................................107
15 Using Pentacam® technology to evaluate corneal scars, planning and documenting
surgery outcomes by Arun C. Gulani, MD, MS..................................................................108-116
15.1 Case 1: Corneal scar with RK incisions and cataract...............................................................112
15.2 Case 2: Keratoconus with congenital cataract, high myopia and high astigmatism.....115
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16 INTACS® implantation...............................................................................................................117-122
16.1 Case 1: by Prof. Michael W. Belin....................................................................................................117
16.2 Case 2: INTACS® after PRK by Alain-Nicolas Gilg, MD............................................................119
16.3 Case 3: INTACS® & crosslinking by Prof. Renato Ambrósio Jr,
Fernando Faria-Correia, MD, Allan Luz, MD................................................................................121
17 Holladay Report & Holladay EKR65 Detail Report by Jack T. Holladay, MD................123-136
17.1 Holladay Report....................................................................................................................................123
17.2 Holladay EKR65 Detail Report.........................................................................................................129
17.3 Case 1: Holladay Report & Holladay EKR65 Detail Report of a normal exam..................130
17.4 Case 2: Holladay Report & Holladay EKR65 Detail Report of a keratoconus exam.........133
17.5 Case 3: Holladay Report & Holladay EKR65 Detail Report of a post LASIK exam............135
18 Corneal tomographic analysis is essential before cataract surgery -
4 steps in screening candidates for premium IOLs by Prof. Naoyuki Maeda.............137-140
18.1 Corneal topography for selecting premium IOLs.......................................................................137
18.2 Step 1: Evaluation of corneal irregular astigmatism.................................................................140
18.3 Step 2: Detection of abnormal corneal shape............................................................................140
18.4 Step 3: Evaluation of corneal spherical aberration...................................................................140
18.5 Step 4: Evaluation of corneal cylinder..........................................................................................140
19 Dependency of effective phacoemulsification time on Pentacam® Nucleus Staging (PNS)
by Mehdi Shajari, MD, Wolfgang Mayer, MD, Prof. Thomas Kohnen............................141-142
19.1 Introduction..........................................................................................................................................141
19.2 Case 1: Low PNS and low EPT.........................................................................................................142
19.3 Case 2: High PNS and high EPT......................................................................................................142
20 Total corneal astigmatism for toric IOL by Giacomo Savini, MD...................................143-148
20.1 Case 1: Cylinder overcorrection from measurement of keratometric astigmatism
in an eye with WTRA..........................................................................................................................144
20.2 Case 2: Cylinder undercorrection from measurement of keratometric astigmatism
in an eye with ATRA...........................................................................................................................146
20.3 Case 3: Cylinder overcorrection from measurement of keratometric astigmatism.........147
21 Overview about IOL power calculation formulas for different eye types............................. 149
22 Phakic IOL implantation .........................................................................................................150-160
22.1 Manual pre-op simulation and post-op control by Eduardo Viteri, MD.............................150
22.1.1 Pre-operative evaluation...................................................................................................150
22.1.2 Post-operative evaluation.................................................................................................151
22.2 3D pIOL Simulation Software and Aging Prediction by Prof. Burkhard Dick,
Sabine Buchner, Optometrist............................................................................................................151
22.2.1 Myopic Artisan/Verisyse, 6/8.5 mm................................................................................151
22.2.2 Toric Artisan/Verisyse, 5/8.5 mm....................................................................................155
22.3 Patient selection criteria by Prof. Burkhard Dick,
Sabine Buchner, Optometrist............................................................................................................157
22.4 Case example of ectasia after LASIK, crosslinking and pIOL implantation
by Prof. Renato Ambrósio Jr, Fernando Faria-Correia, MD, Allan Luz, MD.........................159
Table of contents

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23 Case reports from daily practice.............................................................................................161-172
23.1 Case 1: Cortical cataract by Tobias H. Neuhann, MD................................................................161
23.2 Case 2: Remove sutures after corneal transplant surgery?
by Tobias H. Neuhann, MD................................................................................................................162
23.3 Case 3: Keratoconus and cataract by Tobias H. Neuhann, MD...............................................163
23.4 Case 4: Corneal infiltrate by Prof. Renato Ambrósio Jr ...........................................................166
23.5 Case 5: Incisional edema, by Prof. Renato Ambrósio Jr ...........................................................168
23.6 Case 6: Corneal thinning after herpetic keratitis by Prof. Renato Ambrósio Jr ................169
23.7 Case 7: Epithelial ingrowth after keratomileusis in situ
by Prof. Renato Ambrósio Jr .............................................................................................................171
24 Scheimpflug and slit lamp images..........................................................................................173-178
24.1 Corneal dystrophy.................................................................................................................................173
24.2 Congenital anterior pyramid cataract............................................................................................174
24.3 Posterior capsular cataract.................................................................................................................175
24.4 Nuclear cataract....................................................................................................................................176
24.5 Posterior synechia.................................................................................................................................177
24.6 Pterygium................................................................................................................................................178
25 Orthokeratology, general screening by Alain-Nicolas Gilg, MD......................................179-181
26 Important studies and case reports.......................................................................................182-198
26.1 Refractive studies.................................................................................................................................182
26.2 Case reports............................................................................................................................................191
26.3 Cataract studies....................................................................................................................................191
26.4 Case reports...........................................................................................................................................196
26.5 Glaucoma studies.................................................................................................................................196
26.6 Case reports...........................................................................................................................................198
27 References.................................................................................................................................... 199-201
28 List of illustrations......................................................................................................................202-205
29 Tables directory.....................................................................................................................................207
30 List of abbreviations....................................................................................................................208-209
31 Authors and contact addresses................................................................................................210-211
Table of contents

5
1 Introduction
This guide is intended to assist Pentacam®/Pentacam® HR (referred to here as Pentacam®) users in
interpreting the results and screens of the Pentacam®. We may not have covered everything which
might be of interest, and we therefore ask anyone using the Pentacam® for their help in improving
this guide step by step. Please forward us any cases or observations of particular interest, and we
will be happy to incorporate them in this guide.
This guide cannot, of course, replace the knowledge and experiences that only come from long
years of medical studies and professional practice, but it will be of help in cases of doubt as well
as to beginners. At the same time, since medical findings may also depend on the practitioner’s
personal experience and perceptions, the individual patient’s history or the particular combination
of instruments used, it is quite possible for results obtained by other means to differ from those
shown in this guide yet be nonetheless valid.
2 Description of the unit and general
remarks
The OCULUS Pentacam® is a rotating Scheimpflug camera. The rotational measuring procedure
generates Scheimpflug images in three dimensions, with the dot matrix fine-meshed in the centre
due to the rotation. It takes a maximum of 2 seconds to generate a complete image of the anterior
eye segment. Any eye movement is detected by a second camera and corrected for in the process.
The Pentacam® calculates a 3D model of the anterior eye segment from as many as 25.000
(HR: 138.000) distinct elevation points.
The topography and pachymetry of the entire anterior and posterior surface of the cornea from
limbus to limbus are calculated and depicted. The analysis of the anterior eye segment includes a
calculation of the chamber angle, chamber volume and chamber height and a manual measuring
function that can be applied to any location in the anterior chamber of the eye. Images of the
anterior and posterior surface of the cornea, the iris and the anterior and posterior surface of
the lens are generated in a moveable virtual eye. The densitometry of the lens and cornea is
automatically quantified.
The Scheimpflug images taken during the examination are digitalized in the main unit, and all
image data are transferred to the PC.
When the examination is finished, the PC calculates a 3D virtual model of the anterior eye segment,
from which all additional information is derived.
1 Introduction
2 Description of the unit
and general remarks

6
3 Differences between the various
topography maps of Pentacam®
3.1 Calculation of corneal power
Corneal Placido topographers measure geometrical corneal slope values. These values are converted
into curvature values e.g. values of axial (sagittal) curvature or instantaneous (tangential) curvature
which are initially given in mm. The Pentacam® measures geometrical height (elevation) values,
which are likewise converted into values of axial (sagittal) or instantaneous (tangential) curvature
and given in mm. These geometrical radius (mm) values are commonly converted it into refractive
power values, which are given in diopters (D). This is normally done according the simple formula of
D = (1.3375-1)*(1000)/Rmm.
A. The refractive effect
A sphere (sph) has the same radius of curvature at every point of its surface; however, due to
the phenomenon of spherical aberration (SA) its refractive power is not the same everywhere. If
the effect of SA is not taken into account, a corneal sphere with a radius of, say, 7.5 mm may be
considered to have the same refractive power of 45 D at every point of its surface (assuming the
keratometer calibration index of 1.3375, see below). Due to SA, however, the refractive power in the
periphery is actually higher. The Pentacam® refractive maps, as they are called, are calculated on the
basis of “Snell’s law” of refraction using precision ray tracing, thereby taking this effect into account.
B. Inclusion of anterior/posterior surface
By convention most keratometers use the refractive index of 1.3375 when calculating the dioptric
power of the anterior radius; in doing so they assume the cornea to have a single refracting
surface. However, it has been known for quite some time that this keratometric index is not the
best approximation to the rather physiological power of the cornea. Due to the contribution of
the posterior surface and the more rather refractive index of the cornea (n cornea = 1.376), the
True Net Power of the cornea, calculated using thick lens models or high-precision ray tracing,
is lower than the value reported by standard keratometry. The deviation between True Net Power
and corneal power as determined by standard keratometry (Sim K’s) becomes even greater when
dealing with corneas after excimer laser ablation (LASIK, LASEK and PRK) of the anterior surface.
After refractive corneal surgery it is no longer possible to calculate corneal refractive power based
only on the anterior surface, as the ratio between the anterior and posterior radius of the cornea
has changed considerably. When the calcultio of the total corneal astigmatism comes into focus the
effect of the posterior corneal surface cannot be disregarded anymore. Depending to the orientation
of the anterior and posterior corneal kertometry the total corneal astigmatism can be over or
underestimated and the axis of the total corneal astigmatism is influenced [1].
3 Differences between the various topography maps of Pentacam®

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C. The refractive index
For historical reasons, most Placido topographers and keratometers use the refractive index of 1.3375
for calculating corneal refractive power. However, this refractive index is actually incorrect even for
the untreated eye (n ≈1.332). It assumes the ratio between the anterior and posterior curvature of
the cornea to be constant. Many intraocular lens (IOL) power calculation formulas use the incorrect
‘K-reading’, necessitating empirical correction to obtain the correct IOL power even in normal cases.
Care should also be taken when using ‘K-readings’ from post-LASIK corneas or based on True Net
Power or ray tracing, as the resultant D readings will be out of range for the applied IOL calculation
formulas unless they are corrected for or converted into equivalent keratometer readings (EKR). Some
modern formulas are able to deal with the rather measured curvatures of the front and back surface
of the cornea, however.
D. Location of the principal planes
Calculation of corneal power by ray tracing involves sending parallel light through the cornea.
It must take into account that each light beam is refracted according to the refractive index
(1.376/1.336), the slope of the surfaces, and the exact location of refraction. This is necessary
because the principal planes of the anterior and posterior surface differ slightly from one another due
tocorneal thickness. The Pentacam® is able to measure the anterior as well as the posterior surface of
the cornea. This allows further corrections to be made. The Pentacam® provides a number of different
maps for predicting corneal power.
3.2 Sagittal power map (also called axial power map)
This is the common Placido style map with corneal power calculated using a refractive index of
1.3375 and the simple formula D = (1.3375-1)*(1000)/Rmm. It shows power values (Figure 1) similar
to those of other Placido topographers.
3 Differences between the various topography maps of Pentacam®
Figure 1: Sagittal power map of a sphere, r= 8 mm

8
3.3 Refractive power map
This map (Figure 3) uses only values from the anterior surface, but it also takes effect “A” (see above)
into account. It calculates corneal power according to Snell’s law of refraction assuming a refractive
index of 1.3375 to convert curvature into refractive power (Figure 2). This is a map that other
Placido topographers also may show because it only considers the anterior surface.
Figure 2: Snell´s law of refraction
Figure 3: Refractive power map of a sphere, r = 8 mm
3 Differences between the various topography maps of Pentacam®

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3.4 True Net Power
This map (Figure 4) shows the optical power of the cornea based on two different refractive indices,
one for the anterior (corneal tissue: 1.376) and one for the posterior surface (aqueous humour:
1.336), as well as the sagittal curvature of each. These results are aggregated. The True Net Power
map thus takes effects “A” and "B" into account. The underlying equation is:
Figure 4: True Net Power map calculated by two spheric surfaces of
anterior r = 8 mm and posterior r = 6.58 mm
3 Differences between the various topography maps of Pentacam®
TrueNet Power = 1,376 -1 1,336 -1,376
*1000 + *1000
rant_surface rpost_surface

10
The study to validate the method was conducted using the Holladay 2 formula. Here it was deter-
mined that after LASIK the best correlation with the traditional method, with a mean prediction
error of -0.06 D ± 0.56 D, is obtained using a mean zonal EKR for the 4.5 mm zone. For post-RK
patients, the mean prediction error is –0.04 D ± 0.94 D [2].
3.5 Equivalent Keratometer Readings power map
This map (Figure 5) was designed to take into account the refractive effects of both the anterior
and the posterior surface. Another requirement was that it should output power values which
in normal cases (no Lasik) would be comparable with simulated K (SimK) values, which are
usually derived from sagittal curvature map. Its output is therefore also referred to as Equivalent
Keratometer Readings (EKR). It calculates power according to Snell’s law using the refractive
indices of corneal tissue and aqueous humour and aggregating the values for anterior and posterior
power. Then the output is shifted such that for a normal eye (posterior corneal radius 82% of
anterior corneal radius) its values (EKR) are identical to those of SimK readings from a sagittal map.
In other words, the EKR map is corrected by adding the error that would be created by a refractive
index of 1.3375 in a sagittal map. In this way it provides equivalent K-values (EKR) that can be
used in IOL formulas that correct for n=1.3375. The EKR map thus takes into account effects "A",
"B" and "C".
Figure 5: EKR power map calculated by twospheric surfaces of
anterior r = 8 mm and posterior r = 6.58 mm
3 Differences between the various topography maps of Pentacam®

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3.6 Total Cornea Refractive Power map
This map (Figure 7) uses ray tracing to calculate the refractive power of the cornea. It takes into
account how parallel light beams are refracted according to the relevant refractive indices (1.376
and 1.336), the exact location of refraction and the slope of the surfaces. The location of refraction
is a determinant of surface slope, since the anterior and posterior surfaces have slightly differing
principal planes due to corneal thickness. In this way the map takes effects "A", "B", "C" and
"D" into account. Its results are more realistic than any other, but they will deviate from normal
(sagittal) SimK values so they cannot be used in conventional IOL formulas.
Figure 6: Calculation of power according to Snell´s law taking the different refractive
indices and the different principal planes of the anterior and posterior corneal
surfaces into account
Figure 7: Total Corneal Refractive Power map calculated by two spheric surfaces
of anterior r = 8 mm and posterior r = 6.58 mm and pachimetry
3 Differences between the various topography maps of Pentacam®

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4 Recommended settings and color maps, displays and values
4 Recommended settings and color maps,
displays and values
Physicians who are starting to work with the Pentacam® often turn to us with questions on settings
such as step width on the color scale, or which maps and values to consider before doing LASIK, PRK,
RK or phakic IOL (pIOL) implantation or in keratoconus examinations etc.
In the following chapter we present our recommendations on the more frequently addressed issues.
Hopefully they will also cover most of your questions or even provide new insights as you work
through them. They are no more than recommendations and not necessarily intended to discourage
you from using other maps and settings that you may have found to work best for you.
4.1 Recommended settings
When working through the following chapters it is advisable to consistently use the same settings so
as to be able to reproduce the values given.
 In the elevation maps, use a sphere fitted in float (BFS) and set the calculation diameter to
manual and use 8 mm or 9 mm
 In the scan menu, select “25 images per scan” and “auto release”
 Keratometer presentation: R flat/R steep, unitdiopter (D)
 Corneal form factor asphericity Q:
Q < 0: Untreated cornea, normal case
Q > 1: Treated cornea LASIK/PRK/RK etc
 Color scale: American style
 Step width:
Normal (10 μm) for pachymetry maps
Normal (1 D) for topography maps
Rel. (2.5 μm) Minimum for elevation maps
 Use the 9 mm loupe function to obtain maps comparable with those of Placido based
topographers

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4 Recommended settings and color maps, displays and values
4.2 Recommended color maps, displays and values
4.2.1 Screening for corneal refractive surgery
We recommend using the following maps and analysis displays:
 Fast Screening Report to check whether the displayed parameters are within normal limits
 4 Maps Refractive to check the pachymetry, topography and elevation maps of both corneal
surfaces
 Belin/Ambrósio Enhanced Ectasia Display to check whether there deviations from normal limits
which can be a sign of early ectatic changesor keratoconus
 Zernike Analysis to see whether the LOA or HOA are withon normal limits
 Important values: R flat and R steep, asti and axis, Q-value, QS, pachymetry at thinnest spot and
pupil centers, distance between the corneal apex and thinnest spot. In the elevation maps please
use the parameters recommended in chapter 10.1.2
4.2.2 Pre-op screening for iris fixated phakic IOL implantation
We recommend using the following maps and analysis displays:
 The 3D pIOL Simulation Software and Aging Prediction prior to iris fixated pIOL implantation
(available in the Pentacam® HR only). Calculate the required pIOL power using the implanted
calculator. Use the database to find a pIOL that best matches the patient’s subjective refraction.
Its fit in the anterior chamber is simulated in 3D and the minimum clearances are displayed. The
aging simulation allows a simulation of the pIOL position in up to 30 years. Double-check your
calculations and evaluations with the manufacturer of the respective pIOL
 For all further pIOL e.g. Intraocular Contact Lens (ICL): Scheimpflug images to obtain information
on the dimensions of the anterior chamber, the iris curve and the densitometry of the cornea and
crystal lens. The view of the anterior chamber angle (ACA) shows whether there is an open or
closed angle
 Evaluate the horizontal corneal diameter (HWTW). It is displayed automatically if the new iris
camera optic is built in. If not it can be measured manually in the Scheimpflug image at the 180°
position (horizontal)
 Important values: R flat and R steep, asti and axis, HWTW, Q-value, QS, anterior chamber depth
(ACD) pachymetry in the thinnest spot and in the pupil center

14
4.2.3 Glaucoma screening
We recommend using the following maps and analysis displays:
 Fast Screening Report to check whether the displayed parameters are within normal limits
 General Overview display to view the chamber angle in the Scheimpflug images and corneal
thickness. While clicking to the button “Enter IOP” the tonometrically measured IOP can be
entered manually or the respective IOP change can be viewed. The displayed IOP is based on
pre-programmed IOP corrections tables. For more details refer to the Pentacam® User Guide
 Important values: ACD, ACV, ACA, Q-value, QS, pachymetry, IOP-correction
4.2.4 Cataract surgery and IOL calculation for virgin and post refractive corneas
We recommend using the following maps and analysis displays
 Fast Screening Report to check whether the displayed parameters are within normal limits
 Cataract Pre-OP Display that offers a comprehensive overview. Prof. Maeda recommended the
4 following steps to select the IOL:
1. Evaluation of corneal irregularities
2. Corneal shape assessment
3. Evaluations of corneal spherical aberrations
4. Evaluations of the corneal astigmatism
(An article was published in „The Highlights of Ophthalmology“ Assessment of Corneal Optical
Quality for Premium IOLs with Pentacam®“ Highlights of Ophthalmology • Vol. 39, Nº 4, 2011)
 Zernike Analysis to determine the amount HOA and LOA
 ACD, manual horizontal white-to-white (HWTW) for keratometry readings from virgin eyes
 Scheimpflug images to obtain information on the dimensions of the anterior chamber and the
condition of the crystalline lens. Lens density can be quantified in a single location, a line, an area
or a volume, as desired. The grading PNS can be used for optimizing Phaco settings (doi:10.1016/j.
jcrs.2009.08.032) and for the effective phaco time (http://dx.doi.org/10.1016/j.ajo.2013.09.017)
 The Holladay Report and the Holladay EKR65 Detail Report for a comprehensive overview of the
cornea. This includes the topographic as well as the pachymetry map and the anterior and
posterior elevation maps. For more information refer to chapter 17
 The BESSt formula, developed from Edmondo Borrasio, MD. This requires Rm anterior,
Rm posterior, CCT and ACD doi:10.1016/j.jcrs.2006.08.037
 Okulix or Phaco Optics, which are IOL power calculation software based on the ray tracing
principle. More information can be found under: www.phacoptics.com; www.okulix.de
 Important values: Keratometry, asti and axis, Q-value, QS, ACD, pachymetry in the thinnest spot
and in the pupil center
4 Recommended settings and color maps, displays and values

15
5 Differences between Placido and
elevation-derived curvature maps
by Prof. Michael W. Belin
5.1 Keratoconus in OD and OS?
The case shown below explains the difference between suspicious and significant elevation maps
and numbers. The topographic map (Figure 8) shows the left and right eye but gives no unequivocal
statement if it is a keratoconus or not.
The right eye seems to be fine. The left eye is a little steeper. The Pentacam® 4 Maps Selectable
answers clearly the question.
Figure 8: Placido based topography of OD and OS allowing no conclusion regarding
keratoconus
5 Differences between Placido and
elevation-derived curvature maps

16
The right eye (Figure 9) has a regular corneal thickness, but the elevation maps of the anterior and
posterior surface indicates this cornea as a suspicious cornea. Both sides show an inferior position
of the cone with suspicious elevations.
suspicious elevation
Figure 9: 4 Maps Selectable showing keratoconus-suspicious elevations in OD
5 Differences between Placido and
elevation-derived curvature maps

17
The left eye (Figure 10) indicates an inferior steepening, but a smooth anterior elevation map.
The reason for the thinning in the pachymetry map is the posterior elevation map, where there
are significant elevations of more than 30 μm. Note that the position of the thinning in the
pachymetry map and the highest spot on the elevation map are exactly at the same position.
This is an excellent example to document that topography or anterior elevation only does not
indicate keratoconus.
Figure 10: 4 Maps Selectable showing significant elevation in OS
significant elevation
5 Differences between Placido and
elevation-derived curvature maps

18
5.2 Form fruste keratoconus?
A 47-year-old female presented for a second opinion. She had previously been told she was not a
candidate for refractive surgery and that she had “form fruste” keratoconus.
Her exam had revealed a BSCVA 20/20+ OD, and the slit lamp and external examination findings had
been WNL. However, Placido topography showed the following (Figure 11):
Pentacam® anterior segment analysis revealed normal pachymetry (normal distribution & central
thickness > 650 μm).
The anterior and posterior elevation revealed a slightly decentered apex. This had led to a “false
positive” inferior steepening on the curvature map. Custom LASIK was performed without incident
(Figure 12, Figure 13).
Note:
This case illustrates the limitations of curvature analysis in trying to analyze a shape abnormality.
Curvature is a reference-based measurement and in this case, inaccurately reflects shape
information. Elevation data are independent of axis or orientation and does not have the false
positive rates as curvature maps commonly do.
Figure 11: Placido based topography of OD and OS
5 Differences between Placido and
elevation-derived curvature maps