Transcript Slide 1

Corneal Biomechanical Assessment using
Dynamic Ultra High-Speed Scheimpflug
Technology Non-Contact Tonometry
(UHS-ST NCT): Preliminary Results
R. Ambrósio Jr
&
Rio de Janeiro
Corneal
Tomography
and
Biomechanics
Study Group
Renato Ambrósio Jr., MD, PhD*
Diogo L. Caldas, MD
Isaac C. Ramos, MD
Rodrigo T. Santos, MD
Leonardo N. Pimentel, MD
Cynthia Roberts, PhD*
Michael W. Belin, MD*
Dr. Ambrósio & Dr. Belin are consultants for Oculus Optikgeräte GmbH
(Wetzlar, Germany) and have received research funding and©travel
reimbursements
R. Ambrósio
Jr, MD, PhD - 2011
Introduction:
Evolution on Corneal Propedeutics
“Propedeutics” refers (in Medicine) to the collection of data
about a patient by observations and examinations.
Advances are recognized on the ability for architecture or
goemetrical characterization of the cornea
Keratometry, Keratoscopy, Videokeratography,
Corneal Topography, Corneal Tomography
R. Ambrósio Jr
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Rio de Janeiro
Corneal
Tomography
and
Biomechanics
Study Group
© R. Ambrósio Jr, MD, PhD - 2011
Corneal Biomechanics: Relevance
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Rio de Janeiro
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Tomography
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Biomechanics
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From Geometrical and Optical understanding, the next step is
biological evaluation: healing response and biomechanics
Ectasia mysteries* in Refractive Surgery had highlight the
need for corneal biomechanical understanding
(*ie: cases with no risk factors that develop ectasia after LASIK)
Also to Customize Refractive Corneal Treatments;
correctly measure IOP (intraocular pressure) and to possibly
predict glaucoma risk
Corneal biomechanical evaluations were limited to in vitro
studies and to mathematical finite element models until the
Ocular Response Analyzer (ORA-Reichert, Depew) in 2005
New techniques are under development for evaluating
biomechanics
This e-Poster presents a new system – The Corvis ST (Oculus,
Wetzlar, Germany) with preliminary clinical results.
© R. Ambrósio Jr, MD, PhD - 2011
The Oculus Corvis ST
Ultra High-Speed (UHS ST) Scheimpflug Technology
takes 4,330 frames/sec with 8mm horizontal coverage
Monitors corneal deformation response to a
symmetrically metered air pulse
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Corneal
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1. Natural; (Ingoing Phase) 2. First Applanation (1st A) Momentum; 3 and 4. Ingoing Concavity
Phase; 5. Highest Concavity Momentum; 6. Oscillation Period; (Outgoing Phase); 7. Second
Applanation (2nd A) Momentum; 8. After Second Applanation; 9. Natural Back
1st Applanation, Highest Concavity and 2nd Applanation: Time and Length;
Maximum Deformation; Maximum Velocity In and Out; Thickness
© R. Ambrósio Jr, MD, PhD - 2011
Corvis ST: First Studies
Experiment involving contact lenses mounted on an artifical
pressurized chamber (Caldas et al., ePoster ASCRS 2011) found
that the deformation response is influenced by lens properties and
chamber pressure.
The inspection of the actual deformation process details corneal
characterization, which has a potential for distinguishing normal
(A, B) and keratoconus (C, D) corneas (see video* PosterASCRS2011_clip_RAmbrosio).
Natural and Highest Deformation Momentum in a Normal (A, B) and a Keratoconic (C, D) Cornea
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Corneal
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© R. Ambrósio Jr, MD, PhD - 2011
Corvis ST: Clinical Parameters
IOP: is the NCT measurement based on the 1st Applanation
1st A-time: is the time from starting
until the first applanation
HC-time: time from starting until
Highest Concavity is reached
2nd A-time: time from starting
until the second applanation
1st A length: cord length of the first applanation
2nd A length: cord length of the second applanation
Def Amp: maximum amplitude at the apex (highest concavity)
W-Dist: distance of the two “knee’s” at highest concavity (HC)
Curvature Rad HC: central concave curvature at HC
Curvature Rad normal: initial central convex curvature
Vin: corneal speed during the first applanation moment
Vout: corneal speed during the second applanation moment
R. Ambrósio Jr
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Rio de Janeiro
Corneal
Tomography
and
Biomechanics
Study Group
© R. Ambrósio Jr, MD, PhD - 2011
Clinical Study
The Corvis ST was utilized to assess corneal deformation
response in one eye from 71 keratoconic patients and in one eye
from 178 normal patients.
Clinical diagnosis was based on the complete eye exam, Placidodisk based corneal topography and Pentacam Corneal Tomography.
Statistically significant distributions for all parameters (MannWhitney, p<0.05), but with significant overlap and AUC
(area under the ROC curves) between 0.673 and 0.852
100
Rio de Janeiro
Corneal
Tomography
and
Biomechanics
Study Group
Wilcoon Rank Sum
(Mann- Whitney Test)
IOP:
1st A Time:
2nd A Time:
1st A Length(max):
2nd A Length(max):
Curv. Rad. Normal:
Curv. Rad. HC:
Pachy Apex:
W-Dist.:
Def.Amp.(max):
Vin:
Vout:
< 0.0001
< 0.0001
0.0006
0.0037
0.0008
0.4126
< 0.0001
< 0.0001
0.0191
< 0.0001
< 0.0001
0.0001
80
Sensitivity
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1st A Length(max):
1st A Time:
2nd A Length(max):
2nd A Time:
Curv, Rad, HC:
Def,Amp,(max):
60
40
20
0
0
20
40
60
80
100
100-Specificity
© R. Ambrósio Jr, MD, PhD - 2011
Corvis Combo1: combined parameter
Joint work with “Instituto de Computação” at UFAL
(Universidade Federal de Alagoas*) to develop a combined
parameter (Corvis Combo1) based on a linear regression analysis,
considering the effects of IOP on deformation response parameters
0.033 * IOP - 0.004 * Pachy Apex - 0.448 * 1st A Time - 0.049 * HC Time + 0.093 * 2nd A Time + 0.026 * 1st A
Length(max) - 0.105 * 2nd A Length(max) + 0.208 * Def Amp (max) - 0.619 * W-Dist - 0.021 * Curv, Rad, HC - 0.101 *
Curv, Rad, Normal - 0.525 * Vin - 0.166 * Vout + 7.952
combo1
100
80
Sensitivity
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Ave
SD
Sensitivity: 87,3
Specificity: 89,3
Criterion : >0,2527
N
-0,00801
0,218348
KC
0,506829
0,26691
60
40
20
0
0
20
40
60
80
100
100-Specificity
* Prof. Aydano P. Machado & J. M. Lyra, MD, PhD
© R. Ambrósio Jr, MD, PhD - 2011
Clinical Study
The Corvis ST Combo1 performed statistically better (p<0.05;
Pairwise ROC comparisons) than the individual parameters from the
Corvis ST to distinguish 71 keratoconic eyes and 178 normal eyes
(one eye per patient included)
This approach has been complementary to enhance the diagnosis
of ectasia susceptibility.
AUC
SE a
95% CI b
0,802
0,0313
0,747 to 0,850
1st_A_Time_
Def_Amp__max__
0,749
0,0355
0,691 to 0,802
Pachy_Apex_
0,852
0,0265
0,801 to 0,893
Curv__Rad__HC_
0,852
0,0290
0,802 to 0,894
Curv__Rad__Normal_
0,810
0,0329
0,755 to 0,857
1st A Time:
CorvisST Combo1
0,931
0,0191
0,892 to 0,959
Def,Amp,(max):
a DeLong et al., 1988 b Binomial exact
Pachy Apex:
100
80
Sensitivity
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100
60
80
Curv, Rad, HC:
Curv, Rad, Normal:
combo1
1st A Time:
Def,Amp,(max):
Pachy Apex:
Curv, Rad, HC:
Curv, Rad, Normal:
combo1
40
60
20
40
0
0
20
0
20
40
60
80
100
100-Specificity
© R. Ambrósio Jr, MD, PhD - 2011
Clinical Correlations
There were very significant correlations (Spearman, p<0.001) between IOP
and 1st Applanation Time (rho=0.94), 2nd Applanation Time (rho=-0.73),
Deformation Amplitude (rho=-0.80), W-Dist (rho=-0.66), Curv Rad HC
(rho=0.45), Vin (rho=-0.49), Vout (0.38) and Combo1 (rho=-0.44)
There were significant correlations (Spearman, p<0.01) between Pachymetry
at the Apex and IOP (rho=0.37), 1st Applanation Time (rho=0.4) and Lengh
(rho=-0.18 ), W-Dist (rho=-0.25), Curv Rad HC (rho=0.48), Vout (rho=0.3),
and Combo1 (rho=-0.64)
There was a positive correlation between age and HC Time
(Spearman, p=0.0039; rho=0.22)
R. Ambrósio Jr
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Corneal
Tomography
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Biomechanics
Study Group
© R. Ambrósio Jr, MD, PhD - 2011
Enhanced Screening for Ectasia
Susceptibility
Biomechanical data from Corvis ST enhances the capability to detect very
mild cases of ectasia and also help to characterize stable cases with
asymmetric bow tie and inferior steepening (ABT/IS).
26 eyes diagnosed as Forme Fruste Keratoconus (FFKC), with normal
front curvature map while the fellow eye has keratoconus were examined.
25 eyes with ABT/IS but with no other clinical or tomographic sign of
ectasia were examined.
Combo1
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Rio de Janeiro
Corneal
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Biomechanics
Study Group
24/178 (13%) normal eyes >0.21
9/71 (13%) keratoconic eyes <0.21
21/26 (80%) eyes with FFKC >0.21
8/25 (32%) ABT/IS cases >0.21
Kruskall-Wallis Test
Normal
Normal
KC
FFKC
KC
<0.05
FFKC
<0.05
NS
ABT/IS
NS
<0.05
<0.05
see video* PosterASCRS2011_clip_RAmbrosio
Ave
SD
N
-0,00801
0,218348
171
FFK1
0,345529
0,196043
26
KC
0,506829
0,26691
71
ABT
0,133745
0,181624
25
© R. Ambrósio Jr, MD, PhD - 2011
Corvis ST: Conclusions
The inspection of corneal deformation during NCT enables
biomechanical characterization
The deformation is severely influenced by IOP
Combo1 from Corvis ST provides clinically relevant parameter
to enhance sensitivity and specificity to detect ectasia.
ABT with no Ectasia (A,B) x FFKC (C, D)
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Study Group
This approach is
complementary to
Corneal Tomography
with the Pentacam
for screening
refractive candidates
Combo 1=0.16
Combo 1=0.31
© R. Ambrósio Jr, MD, PhD - 2011