1. ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
Bruno Valbon, Ana Caiado, Ricardo Louzada, Renato Ambrosio Jr *.
Purpose : To study corneal biomechanical changes after clear cornea cataract surgery and to correlate with corneal thickness and corneal tomographic parameters.
Rio de Janeiro – Brasil 2010
* Dr. Ambrosio is a consultant to Oculus and in the speaker bureau for Reichert, Alcon and Allergan

2. ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
Methods:
12 eyes from 11 patients who had uneventful clear cornea phacoemulsification and foldable IOL implantation were included.
Corneal tomography based on a rotating Scheimpflug camera (Oculus Pentacam) and corneal biomechanical properties measurements by the ORA (Ocular Response Analyzer – Reichert) were performed preoperatively and in the first day (D1).
Central corneal thickness (CCT) and Ambrósio’s pachimetric progression indices from the Pentacam were correlated with ORA waveform-derived parameters.
The Wilcoxon signed-rank test was used to evaluate if each variable for the comparisons of differences between measurements.
Pachimetric Parameters (TP, RPI Min, RPI Mid, RPI Max, ART- Min, ART-Mid and ART-Max) were correlated with ORA waveform-derived parameters (IOPg, IOPcc, CRF, CH, aindex, p1area, uslope2, dive1, path2, mslew1, mslew2, p1area1, uslope11, h21, path11 and path21)
The correlations were evaluated with Spearman rank correlation. A P value lower than 0,05 was considered statistically significant.
Valbon B., Caiado A., Louzada R., Ambrosio Jr., R

3. ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
Pré-op D1 D7
Pentacam Ambrósio’s pachimetric progression indices ( automatically obtained from index LOAD) :
TP (Thinnest Point)
RPI Min, RPI Mid, RPI Max
3) ART- Min, ART-Mid and ART-Max * ART (Ambrósio’s Relational Thinnest ): ART Min=TP/RPI Min; ART Mid=TP/RPI Mid; ART Max=TP/RPI Max D0
Valbon B., Caiado A., Louzada R., Ambrosio Jr., R

4. DESCRIPTION OF ORA WAVEFORM PARAMETERS
ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
DESCRIPTION OF ORA WAVEFORM PARAMETERS
Original ORA Waveform Parameters
Original parameters all Pressure and CDS associated
(CDW - corneal deformation waveform)
IOPg - Goldmann correlated IOP (P1+P2)/2
IOPcc - corneal compensated IOP (P *P1)
CH - corneal hysteresis (P1 - P2)
CRF - corneal rsistance factor (P *P2)
Categories of ORA Waveform Parameters
Pressure associated - 4: IOPg, IOPcc, CH, CR
Areas - 4: area1, area2, area11, area21
Heights - 4: h1, h2, h11, h21
Widths - 4: w1, w2, w11, w21
Aspect ratios -4: aspect1, aspect2, aspect11, aspect21
Slopes - 8; uslope1, dslope1, uslope2, dslope2, etc
Slew rates - 4: slew1, slew2, mslew1, mslew2, etc
Paths - 4, path1, path2, path11, path21
Irregularity - 2: aindex, bindex
Dive - 2: dive 1, dive2
High Frequency 1: aplhf
Waveform Score 1: WS
Valbon B., Caiado A., Louzada R., Ambrosio Jr., R

5. ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
h1, h2, w1, w2,
height - from lowest to highest point in peak
width - at the “base” of peak region
p1area, p2area
area of peak 1, peak 1
uslope1, uslope2
rate of increase from BASE to PEAK
PEAK
PEAK h1
uslope 1 w1
Uslope 2
25% point
BASE
25% point
BASE
mslew 1,mslew 2
maximum single increase in the rise of peak 1,2
longest continuous line w/o a break
dive1, dive2
backside of “downslope” of peak1, peak2
absolute value of peak from peak 1, peak 2 until the first break
aindex, bindex
“smoothness” of peak 1, peak 2
number of breaks in the peak or
how many times the peak changes direction
PEAK
aindex
mslew 1
Dive 1
mslew 2
FIRST BREAK
25% point
25% point
BASE
Valbon B., Caiado A., Louzada R., Ambrosio Jr., R

6. ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
Results :
12 eyes of 11 patients were studied.
Table 1 show statistically significant differences in the variables from Pre-op and D1.
Tables 2 and 3 provide the data on the statistically significant correlations between pachymetric and biomechanical parameters for the Pre-op and D1.
An increase in corneal thickness was observed in all cases in the first day.
Edema was associate with a lower pachymetric progression.
An opposite phenomenon was observed for biomechanical parameters. There was a significant decrease of biomechanical parameters in the first day.
Valbon B., Caiado A., Louzada R., Ambrosio Jr., R

7. Table 1: Comparisons of differences between measurements Pre-op and D1
CCT TP
RPI Min
RPI Mid
RPI Max
ART Min
ART Mid
ART Max
Wilcoxon p<0,05
P-value
0,0011
0,2668
0,022
0,0372
0,2651
0,0115
0,0356
Pre-op and D1
IOPg
IOPcc CH
CRF
aindex
p1area
Uslope 2
dive1
Wilcoxon p<0,05
P-value
0,0299
0,2668
0,0207
0,0014
0,0011
0,003
0,006
0,3474
Pre-op and D1
path2
mslew1
mslew2
p1area
uslope11
h21
path11
path21
Wilcoxon p<0,05
P-value
0,0048
0,0388
0,0054
0,0019
0,0024
0,0583
0,0207
0,0356
Avg
CCT TP
RPI Min
RPI Mid
RPI Max
ART- Min
ART-Mid
ART-Max
PRE
571.75
(Sd 40.39)
551.25
(Sd 30.55)
-0.38
(Sd 3.77)
0.91
(Sd 0.42)
2.31
(Sd 2.87)
981.24
(Sd )
565.60
(Sd )
383.89
(Sd ) D1
720.33
(Sd )
639.5
(Sd 58.69)
0.71
(Sd 0.33)
1.57
(Sd 0.58)
2.72 (Sd1.09)
1190.7
(Sd )
469.05
(Sd )
279.42
(Sd553.84)
Avg
aindex
p1area
uslope2
dive1
path2
mslew1
mslew2
p1area1
uslope11
h21
path11
path21
PRE
8,702
3,544,659
95,410
389
34,199
176
161
1,219,794
67,873
203,500
35,623
44,526 D1 10
5,283,042
66,437
151,083
25,446
22,422
35,723
2,016,910
53,540
207,193
24,991
36,349

8. Correlations with statistically significant differences
ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
Correlations with statistically significant differences
Tables 2 and 3
PRE
CCT X path2
CCT X mslew2
RPI Mid x IOPcc
RPI Max x p1area
ART Min x dive 1
ART Mid x p1area1
ART Max x p1area1
* RS = Coeficient Spermann RS
0,568
-0,563
-0,630
-0,617
0,692
0,680
0,557
TABLE 2
P-value
0,05
0,02
0,03
0,012
0,014 D1
TP x uslope 2
TP x p1area1
RPI Min x CRF
RPI Max x IOPcc
* RS = Coeficient Spermann RS
-0,833
-0,6351
-0,6347
-0,6303
TABLE 3
P-value
0,0007
0,0264
0,0266
0,02
Valbon B., Caiado A., Louzada R., Ambrosio Jr., R

9. Graphics - Correlations with statistically significant differences
ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
Graphics - Correlations with statistically significant differences
Valbon B., Caiado A., Louzada R., Ambrosio Jr., R

10. Graphics - Correlations with statistically significant differences
ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
Graphics - Correlations with statistically significant differences
Valbon B., Caiado A., Louzada R., Ambrosio Jr., R

11. ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
Conclusions:
Corneal edema after cataract surgery is related to a significant attenuation in the thickness profile (lowering of RPI Mid and RPI Max) and with a significant decrease in corneal biomechanical parameters measured by the ORA (including CH and CRF).
Aindex was the best waveform-derived parameter and CCT, TP of the most significant pachimetric parameters (Wilcoxon).
There was a trend for inverting the direction of the correlations between pachymetric and biomechanical parameters from Pre-op and D1. The most important ones were:
ART Min x dive1: 0.69 in Pre-op and in D1; TP x p1area1 : -0,2671 in Pre-op and 0,1086 in D1; RPI Min x CRF : 0,1130 in Pre-op and -0,1634 in D1.
This study demonstrates there is an inverted correlation between thickness parameters and corneal biomechanical properties in the presence of corneal edema.
There is a trend to return to the normal pre-operative values and similar correlations as the Pre-op up to 1 month post-operatively
Valbon B., Caiado A., Louzada R., Ambrosio Jr., R

12. Renato Ambrósio Jr., MD, PhD
ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
ORA Waveform Analysis of Corneal Biomechanical Changes after Clear Cornea Phacoemulsification
Bruno Valbon, MD
Ana Laura C. Canedo, MD
Ricardo Louzada, MD
Renato Ambrósio Jr., MD, PhD