Arq. Bras. Oftalmol.
Arquivos Brasileiros de Oftalmologia
Arq. Bras.
Oftalmol.
0004-2749
1678-2925
Objetivo:
Avaliar a concordância entre as medidas de elevação e curvatura das superfícies
anterior e posterior da córnea obtidos pelos analisadores de Scheimpflug Galilei e
Pentacam.
Método:
Estudo de teste diagnóstico, prospectivo, não-intervencional realizado no
Departamento de Oftalmologia do Centro Médico da Universidade Americana de
Beirute. Sessenta olhos de 60 pacientes consecutivos. As medições foram feitas
usando dois analisadores Scheimpflug diferentes (Galilei e Pentacam). A esfera de
melhor ajuste foi fixada em 8 mm para ambos equipamentos. Paquimetria (CCT),
elevação anterior (AE) e elevação posterior (PE), e curvatura foram avaliados.
Coeficientes de correlação de Pearson, comparação das médias, e gráficos de
Bland-Altman foram utilizados para avaliar a correlação.
Resultados:
A média de CCT (no ápice da córnea) foi 533 ± 35 µm usando o Galilei e 532 ± 37 µm
usando o Pentacam (p=0,980). As médias centrais de AE foram de 1,25 ± 3,95 µm e
2,29 ± e 5,28 µm com o Galilei e Pentacam, respectivamente (p=0,964). As médias de
centrais de PE foram 4,19 ± 8,18 µm e 5,42 ± 14,05 µm com a Galilei e Pentacam,
respectivamente (p=0,956).
Conclusões:
Os analisadores de Scheimpflug avaliados correlacionam bem em termos de
paquimetria, elevação e curvatura.
INTRODUCTION
Corneal laser surgery is currently the most widely used surgical method for correcting
refractive errors. Measurement of the corneal curvature, thickness, and elevation are
important for the preoperative assessment of patients requiring refractive surgery and
for the diagnosis of corneal ectasias like keratoconus and pellucid marginal
degeneration. Historically, a simple Placido-based corneal topography was considered the
norm for screening the cornea for topographic anomalies. Currently, Scheimpflug and
Placido systems are being used to provide information on the anterior and posterior
corneal surfaces. Currently, 2 such systems are widely used: the Galilei Dual
Scheimpflug Analyzer (Ziemer, SIS, Port, Switzerland) and the Pentacam (OCULUS
Optikgeräte GmbH, Germany) single Scheimpflug analyzer.
The present study aims to evaluate the agreement in measurements obtained by these 2
systems. Previous studies have evaluated the agreement between Scheimpflug devices;
however, different best-fit sphere (BFS) diameters were used in both
devices(1) or only
elevation data were compared between the Dual Scheimpflug Analyzer and a Scanning
Slit-beam imaging system(2). Comparisons using different BFS would alter the elevation data
obtained by the single Scheimpflug system (compared with the dual Scheimpflug system)
because the reference is flatter. Now that the pre-set BFS diameter in the single
Scheimpflug system is universally set to 8.0 mm, we attempted a comparison with equal
BFS diameters in both systems. Our aim was not to demonstrate the superiority of one
system over the other, but to discuss the similarities between both systems.
METHODS
This prospective, noninterventional, diagnostic study comprised 60 eyes of normal
candidates for refractive surgery. Patients who had undergone previous ocular surgeries,
those with any systemic disease (including diabetes mellitus, connective tissue disease,
hypertension, and collagen vascular diseases), and/or those who had worn rigid contact
lenses in the past 6 months were excluded. Soft contact lens wearers were asked to
discontinue wearing their contact lenses for at least 14 days prior to
measurements(3). The
study received the approval of the Institutional Review Board of the American University
of Beirut and complied with the Health Insurance Portability and Accountability Act
(HIPAA) recommendations. Informed consent was obtained from all patients. All subjects
underwent corneal topography using the Galilei (dual Scheimpflug system) followed by
corneal topography using the Pentacam (single Scheimpflug system) by the same trained
ophthalmic technician who was blinded to the study protocol.
Pentacam (single Scheimpflug system)
The Pentacam system uses a single rotating Scheimpflug camera (180º) and a
monochromatic slit-light source [blue light-emitting diode (LED) at 475 nm] that
rotate together around the optical axis of the eye to calculate a 3-dimensional (3D)
model of the anterior segment. The 3D, high-resolution, cornea-scanning mode obtains
50 images of the eye in 1 second. Overall, 138,000 true elevation points were
recorded.
Galilei (dual Scheimpflug system)
The Galilei Dual Scheimpflug Analyzer uses two rotating Scheimpflug cameras
integrated with a Placido topographer. The light source is also monochromatic (blue
LED at 475 nm). The 122,000 data points are analyzed per scan. The system used
Scheimpflug images of all anterior segment structures (cornea, iris, pupil, anterior
chamber, and lens) to evaluate and analyze the corneal shape and thickness, pupil
size, and anterior chamber parameters (size, volume, and angle). The presence of two
Scheimpflug camera devices that obtain images of the same part of the eye
simultaneously decreases movement artifacts and increases image accuracy by
superimposing the two images. The presence of the Placido improves the accuracy of
calculation of the anterior corneal curvature.
Measurement technique
Measurements were obtained in a semi-lit room. To standardize the tear film meniscus
and account for tear film abnormalities that may influence Placido measurements, a
drop of carboxymethyl cellulose artificial tears was instilled in the fornix of each
eye, and measurements were obtained 3 min later to ensure that the tear film meniscus
was back to its normal thickness(4). Both eyes were measured. Measurements were obtained using
an 8.0-mm diameter BFS, which was fitted in float. Central elevations and
maximum/minimum elevations in the central 8 mm of the cornea were recorded with both
the dual and single Scheimpflug systems. Pachymetry measurements were internally
calculated by the individual machines by subtracting the anterior and posterior
corneal elevations. In patients with a normal topography, only one eye was considered
for analysis (60 eyes of 60 patients). Data from the right eyes of the first, third,
and fifth 10 patients and data from the left eyes of the second, fourth, and sixth 10
patients were used for further analysis.
Intraclass correlation coefficients (ICCs)
For each system and for a defined subset of apparently healthy eyes, measurements
were obtained 3 times and the data were averaged. One eye of each subject was
selected. Ten right eyes were selected from the first 10 subjects and 10 left eyes
were chosen from the second 10 subjects. The internal repeatability of each machine
was analyzed by calculating the ICC, which was defined as the ratio of the
between-subjects variance to the sum of the pooled within-subject variance and
between-subjects variance. The ICC, which approached 1.0 when there was no variance
between repeated measurements, was automatically calculated using PASW Statistics
software (SPSS version 18.0, SPSS Inc. Chicago, IL, USA). The ICCs ranged from 0 to 1
and were commonly classified as follows: ICC <0.75, poor agreement; 0.75-<0.90,
moderate agreement; and >0.90, high agreement(5).
Statistical analysis
Statistical analysis was performed using the Statistical Program for Social Sciences
v18.0 (SPSS v18.0, SPSS Inc. Chicago, IL, USA). A paired t-test was
used to compare the instruments in each elevation parameter. Mean algebraic and mean
absolute differences were calculated. Results are expressed as means ± standard
deviations. In addition, Pearson's correlation coefficients (PCCs) were calculated to
assess the correlation between the anatomical parameters measured by each imaging
technique. All tests were 2-tailed. A p-value of <0.05 was
considered statistically significant. Bland-Altman plots were used to assess the
interchangeability (agreement) of the 2 imaging systems for measuring elevation
parameters. These plots show the differences between the methods plotted against the
mean of the methods. They provided a graphical method to assess the presence of an
agreement between the 2 clinical techniques.
RESULTS
Patient characteristics
Sixty eyes of 60 subjects (25 males, 35 females) were included in the study. The mean
age of the participants was 27.0 ± 4.1 years. All eyes had a normal topography, with
no evidence of curvature abnormalities.
Machine characteristics
Each measurement was obtained 3 times, and only the findings with the highest quality
(as determined by the machine) were included for analysis. The ICC was calculated for
each machine on the basis of 3 measurements. The ICC for the dual Scheimpflug system
was as follows: 0.999 for pachymetry (CCT), 0.998 for SimK, 0.998 for anterior BFS,
and 0.993 for posterior BFS. The ICC for the single Scheimpflug system was as
follows: 0.994 for CCT, 0.986 for SimK, 0.996 for anterior BFS, and 0.991 for
posterior BFS.
Pachymetry
Pachymetry measurements are summarized in table
1. The mean difference between the dual Scheimpflug and single Scheimpflug
systems in central pachymetry measurements was 0.7 ± 8.2 µm. The mean absolute
difference between the two machines in central pachymetry measurements was 6.7 ± 4.6
µm. Figure 1 shows a Bland-Altman plot of
central pachymetry. The dual Scheimpflug system exhibited a trend for displaying
values larger than those displayed by the single Scheimpflug system for corneal
thicknesses below 550 µm. It also exhibited a tendency to display smaller
measurements at higher mean central pachymetry measurements. The PCC for central
corneal thickness was 0.977.
Table 1
Correlation of pachymetry measurements between the dual Scheimpflug system
(Galilei) and the single Scheimpflug system (Pentacam)
(µm)
Galilei (µm)
Pentacam (µm)
Pearson's correlation coefficient
Central pachymetry
535 ± 35
534 ± 37
0.977
Thinnest point
531 ± 37
528 ± 43
0.982
Superior 2 mm
574 ± 33
590 ± 33
0.864
Inferior 2 mm
568 ± 38
559 ± 43
0.949
Nasal 2 mm
578 ± 32
579 ± 34
0.897
Temporal 2 mm
549 ± 33
553 ± 34
0.904
Superior 3 mm
612 ± 35
649 ± 37
0.889
Inferior 3 mm
613 ± 35
613 ± 39
0.865
Figure 1
A Bland-Altman plot of percentage differences in average central pachymetry
(CCT) measurements between the dual Scheimpflug system (Galilei) and the single
Scheimpflug system (Pentacam).
Anterior and posterior elevation
The anterior elevation measurements recorded by the 2 machines are summarized in
table 2. Posterior elevation measurements
recorded by the 2 machines are summarized in Table
3. The mean difference in between the dual and single Scheimpflug systems
in central AE and central PE measurements was -1.04 ± 2.48 µm and -1.38 ± 7.08 µm,
respectively. The mean absolute difference between the dual and single Scheimpflug
systems in central AE and central PE measurements was 1.85 ± 1.86 µm and 2.77 ± 6.10
µm, respectively. Anterior and posterior Bland-Altman plots of central elevation are
shown in figure 2. A similar trend was observed
for pachymetry measurements, with the dual Scheimpflug system showing higher and
lower values than the single Scheimpflug system for lower and higher elevations,
respectively. The PCC for central anterior elevation was 0.952, while that for
central posterior elevation was 0.974.
Table 2
Correlation of central anterior elevation measurements between the dual
Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam)
(µm)
Galilei
Pentacam
Pearson's correlation coefficient
Central elevation
2.48 ± 2.98
4.23 ± 4.57
0.952
Superior 2 mm
-8.05 ± 10.43
-8.25 ± 12.79
0.933
Inferior 2 mm
-1.10 ± 6.06
1.35 ± 12.81
0.871
Nasal 2 mm
0.35 ± 4.14
-0.55 ± 5.01
0.784
Temporal 2 mm
1.30 ± 4.37
1.68 ± 4.49
0.749
Superior 3 mm
-8.43 ± 8.73
-12.08 ± 10.33
0.742
Inferior 3 mm
-10.18 ± 9.89
-9.30 ± 7.11
0.685
Table 3
Correlation of central posterior elevation measurements between the dual
Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam)
(µm)
Galilei
Pentacam
Pearson's correlation coefficient
Central elevation
5.33 ± 7.69
7.15 ± 14.75
0.974
Superior 2 mm
-20.43 ± 16.49
-22.63 ± 24.59
0.961
Inferior 2 mm
-3.25 ± 11.79
2.33 ± 26.92
0.807
Nasal 2 mm
1.23 ± 10.84
2.73 ± 11.64
0.804
Temporal 2 mm
4.50 ± 11.86
5.25 ± 12.27
0.961
Superior 3 mm
-22.65 ± 10.75
-35.03 ± 17.11
0.706
Inferior 3 mm
-24.95 ± 17.77
-26.53 ± 18.26
0.963
Figure 2
A Bland-Altman plot of differences in average central anterior elevation
(AE) (left) and central posterior elevation (PE) (right) measurements between
the dual Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam).
Keratometric values
Keratometric measurements recorded by the two machines are summarized in table 4. The mean difference in anterior radii
between the dual and single Scheimpflug systems in steep and flat meridians were
-0.05 mm and -0.02 mm, respectively. The mean absolute difference in anterior steep
and flat meridian radii between the dual and single Scheimpflug systems was 0.08 ±
0.14 mm and 0.06 ± 0.07 µm, respectively. The mean difference in posterior steep and
flat meridian radii between the dual and single Scheimpflug systems was -0.02 mm and
-0.06 mm, respectively. The mean absolute difference in the posterior steep and flat
meridian radii between the dual and single Scheimpflug systems was 0.08 ± 0.08 mm and
0.11 ± 0.12 µm, respectively. The PCC for central average keratometry was 0.931.
Table 4
Correlation of corneal keratometric measurements between the dual
Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam)
(µm)
Galilei
Pentacam
Pearson's correlation coefficient
Central average keratometry (D)
45.14 ± 3.20
44.81 ± 3.02
0.931
R steep front (mm)
7.43 ± 0.46
7.46 ± 0.44
0.979
R flat front (mm)
7.66 ± 0.42
7.68 ± 0.40
0.984
R steep back (mm)
6.02 ± 0.47
6.03 ± 0.48
0.968
R flat back (mm)
6.36 ± 0.45
6.42 ± 0.40
0.946
DISCUSSION
Our results demonstrated that both the Galilei Dual Scheimpflug Analyzer and the
Pentacam Single Scheimpflug Analyzer display similar values for the same subjects
measured in terms of keratometric readings, anterior and posterior elevations, and
pachymetry. Both machines gave values comparable with the points lying along the line of
equality, with small limits of agreements (Figures
1 and 2). Previous studies have reported
good correlations between both machines in either pachymetry or corneal power
measurements(6-8).
One of the main diagnostic tools for keratoconus and keratectasia is abnormal
topography. Threshold values of topography, beyond which the topography would be labeled
as abnormal, are specific for each machine. Problems with the existence of 2 systems
will make it more difficult to set common standard cut-off values. In addition,
refractive surgery physicians who have access to both systems may be faced with the need
to compare serial images of the same patient using 2 different machines. Machine
threshold values were first studied on the Orbscan (Bausch and Lomb)(2,9-11) and later
on the Pentacam(12,13). With the availability of the Galilei
Dual Scheimpflug Analyzer, the primary concern was whether values obtained using the
dual Scheimpflug system correlated with those obtained using the single Scheimpflug
system and whether images captured by both systems can be safely compared. Our study
showed that the 2 systems were strongly correlated in terms of keratometry, anterior and
posterior elevation, and pachymetry measurements. Therefore, a conclusion or a trend in
values in a specific patient can be generalized from the single Scheimpflug system and
applied to the dual Scheimpflug system when considering threshold values and overall
patterns. Our results, in terms of pachymetry, were in agreement with those published by
Jahadi-Hoseini et al.(6).
The central keratometric, curvature, and pachymetric values showed a high correlation
(and high agreement) and were not very different between both systems. As we moved
peripherally, the correlation remained high, albeit not as strong as that in the central
area. Similarly, other authors have reported an increase in variability in corneal
pachymetry measurements from the center to the periphery, particularly in the superior
cornea(4,14-17). They attributed this variability to the effects of the
superior eyelid(4). We
believe that the differences observed in paracentral (peripheral) values were very
predictable because small decentration in the BFS would lead to a false high value,
considering that the peripheral cornea is farther away from the BFS because of its
prolate shape. Even within the same system, small decentrations in BFS can manifest as
large deviations in peripheral elevation. The effects of contact lenses on corneal
elevation and curvature have been eliminated from the equation because all subjects were
advised to stop wearing soft contact lenses for at least 2 weeks(3); furthermore, all subjects that had
worn rigid contact lenses in the past 6 months were excluded from the study. The images
were obtained on the same day, thus decreasing any additional confounding factors.
Keratometric values in both machines, despite the fact that they were obtained in a
different manner, showed a high degree of correlation between both systems; keratometric
values with the dual Scheimpflug system were obtained mainly from the Placido image and
were only complemented by the rotating Scheimpflug cameras, while keratometry using the
single Scheimpflug system relied solely on information from the Scheimpflug images.
The objective of our paper was not to show the advantage of one system over the other,
but to assess the degree of correlation. A previously published study showed a
difference between the single and dual Scheimpflug systems, with values obtained by the
former system (Pentacam) being higher than those obtained by the latter
(Galilei)(1). We believe
that the difference was primarily due to the different BFS diameters pre-set for each
system: 9 mm in the single Scheimpflug system and 8 mm in the dual Scheimpflug system.
Current versions of the Pentacam software, similar to the software used in our study,
have adopted the 8-mm pre-set BFS diameter. The fact that both machines showed similar
results for all indices made it possible to compare the follow-up findings of patients
obtained with these two systems, provided the radius of the BFS was set to 8 mm in both
machines.
The reason for incorporating two Scheimpflug cameras may solely be patency issues. The
strong correlation between measurements obtained by both systems does not preclude the
potential advantages offered by the dual Scheimpflug system over the single Scheimpflug
system; in theory, the former should be less sensitive to eye movements while obtaining
pachymetry measurements. This theoretical advantage could be translated into a clinical
one only in a small subset of patients with eye movements beyond a certain critical
threshold. Therefore, potential advantages of the dual Scheimpflug system observed in
some patients would be easily diluted while evaluating aggregate results. Further
studies with the objective of testing the theoretical advantages of the dual Scheimpflug
system and comparing them with those of a gold standard system are required.
Our study was limited by the small sample size.
In conclusion, the single and dual Scheimpflug analyzers correlated well in terms of
pachymetry, anterior and posterior elevation, and curvature measurements.
Funding: No specific financial support was available for this study.
Study carried out at Department of Ophthalmology in the American University of Beirut
Medical Centre, Beirut, Lebanon. Presented in 2010 ASCRS meeting in Boston
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Autoria
Daoud Charbel Fahd
Department of Ophthalmology in the American
University of Beirut Medical Centre, Beirut, LebanonAmerican University of Beirut Medical
CentreLebanonBeirut, LebanonDepartment of Ophthalmology in the American
University of Beirut Medical Centre, Beirut, Lebanon
Carole George Cherfan
Department of Ophthalmology in the American
University of Beirut Medical Centre, Beirut, LebanonAmerican University of Beirut Medical
CentreLebanonBeirut, LebanonDepartment of Ophthalmology in the American
University of Beirut Medical Centre, Beirut, Lebanon
Shady Tanus Awwad Correspondence address: Shady T. Awwad. Director of Laser and Refractive
Surgery Division - Department of Ophthalmology - American University of Beirut
Medical Centre, Beirut, Lebanon. E-mail: sawwad@gmail.com
Department of Ophthalmology in the American
University of Beirut Medical Centre, Beirut, LebanonAmerican University of Beirut Medical
CentreLebanonBeirut, LebanonDepartment of Ophthalmology in the American
University of Beirut Medical Centre, Beirut, Lebanon
Correspondence address: Shady T. Awwad. Director of Laser and Refractive
Surgery Division - Department of Ophthalmology - American University of Beirut
Medical Centre, Beirut, Lebanon. E-mail: sawwad@gmail.com
Disclosure of potential conflicts of interest: D.C. Fahd, None; C.G.
Cherfan, None; C. Raad, None; M. Asouad, None; S.T. Awwad, None.
SCIMAGO INSTITUTIONS RANKINGS
Department of Ophthalmology in the American
University of Beirut Medical Centre, Beirut, LebanonAmerican University of Beirut Medical
CentreLebanonBeirut, LebanonDepartment of Ophthalmology in the American
University of Beirut Medical Centre, Beirut, Lebanon
Figure 1
A Bland-Altman plot of percentage differences in average central pachymetry
(CCT) measurements between the dual Scheimpflug system (Galilei) and the single
Scheimpflug system (Pentacam).
Figure 2
A Bland-Altman plot of differences in average central anterior elevation
(AE) (left) and central posterior elevation (PE) (right) measurements between
the dual Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam).
Table 2
Correlation of central anterior elevation measurements between the dual
Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam)
Table 3
Correlation of central posterior elevation measurements between the dual
Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam)
Table 4
Correlation of corneal keratometric measurements between the dual
Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam)
imageFigure 1
A Bland-Altman plot of percentage differences in average central pachymetry
(CCT) measurements between the dual Scheimpflug system (Galilei) and the single
Scheimpflug system (Pentacam).
open_in_new
imageFigure 2
A Bland-Altman plot of differences in average central anterior elevation
(AE) (left) and central posterior elevation (PE) (right) measurements between
the dual Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam).
open_in_new
table_chartTable 1
Correlation of pachymetry measurements between the dual Scheimpflug system
(Galilei) and the single Scheimpflug system (Pentacam)
(µm)
Galilei (µm)
Pentacam (µm)
Pearson's correlation coefficient
Central pachymetry
535 ± 35
534 ± 37
0.977
Thinnest point
531 ± 37
528 ± 43
0.982
Superior 2 mm
574 ± 33
590 ± 33
0.864
Inferior 2 mm
568 ± 38
559 ± 43
0.949
Nasal 2 mm
578 ± 32
579 ± 34
0.897
Temporal 2 mm
549 ± 33
553 ± 34
0.904
Superior 3 mm
612 ± 35
649 ± 37
0.889
Inferior 3 mm
613 ± 35
613 ± 39
0.865
table_chartTable 2
Correlation of central anterior elevation measurements between the dual
Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam)
(µm)
Galilei
Pentacam
Pearson's correlation coefficient
Central elevation
2.48 ± 2.98
4.23 ± 4.57
0.952
Superior 2 mm
-8.05 ± 10.43
-8.25 ± 12.79
0.933
Inferior 2 mm
-1.10 ± 6.06
1.35 ± 12.81
0.871
Nasal 2 mm
0.35 ± 4.14
-0.55 ± 5.01
0.784
Temporal 2 mm
1.30 ± 4.37
1.68 ± 4.49
0.749
Superior 3 mm
-8.43 ± 8.73
-12.08 ± 10.33
0.742
Inferior 3 mm
-10.18 ± 9.89
-9.30 ± 7.11
0.685
table_chartTable 3
Correlation of central posterior elevation measurements between the dual
Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam)
(µm)
Galilei
Pentacam
Pearson's correlation coefficient
Central elevation
5.33 ± 7.69
7.15 ± 14.75
0.974
Superior 2 mm
-20.43 ± 16.49
-22.63 ± 24.59
0.961
Inferior 2 mm
-3.25 ± 11.79
2.33 ± 26.92
0.807
Nasal 2 mm
1.23 ± 10.84
2.73 ± 11.64
0.804
Temporal 2 mm
4.50 ± 11.86
5.25 ± 12.27
0.961
Superior 3 mm
-22.65 ± 10.75
-35.03 ± 17.11
0.706
Inferior 3 mm
-24.95 ± 17.77
-26.53 ± 18.26
0.963
table_chartTable 4
Correlation of corneal keratometric measurements between the dual
Scheimpflug system (Galilei) and the single Scheimpflug system
(Pentacam)
(µm)
Galilei
Pentacam
Pearson's correlation coefficient
Central average keratometry (D)
45.14 ± 3.20
44.81 ± 3.02
0.931
R steep front (mm)
7.43 ± 0.46
7.46 ± 0.44
0.979
R flat front (mm)
7.66 ± 0.42
7.68 ± 0.40
0.984
R steep back (mm)
6.02 ± 0.47
6.03 ± 0.48
0.968
R flat back (mm)
6.36 ± 0.45
6.42 ± 0.40
0.946
Como citar
Fahd, Daoud Charbel et al. Índices da córnea anterior e posterior com dois analisadores Scheimpflug. Arquivos Brasileiros de Oftalmologia [online]. 2014, v. 77, n. 1 [Acessado 4 Abril 2025], pp. 17-20. Disponível em: <https://doi.org/10.5935/0004-2749.20140006>. ISSN 1678-2925. https://doi.org/10.5935/0004-2749.20140006.
Conselho Brasileiro de OftalmologiaRua Casa do Ator, 1117 - cj.21, 04546-004 São Paulo SP Brazil, Tel: 55 11 - 3266-4000, Fax: 55 11- 3171-0953 -
São Paulo -
SP -
Brazil E-mail: abo@cbo.com.br
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