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ELEVATION AND PACHYMETRY VALUES IN
NORMAL CORNEAS OBTAINED BY GALILEI
ASCRS Boston April 9 -14 2010
Vision Sana Research Group Cornea and Refractive Surgery Unit
Clinica de Oftalmologia de Cali Cali-Colombia
Claudia Blanco Marín MD.Maria Ximena Núñez MD.
The authors have no financial interest in the subject matter of this poster.
To obtain the topographic parameters in normal corneas of candidates for refractive surgery with the Galilei dual-Scheimpflug analyzer and compare them with the Orbscan II scanning-slit system.
PURPOSE
METHODS Prospective study Two measurements per eye from each patient and each device
were taken by the same operator. To obtain equal conditions in elevation measurements, the
Orbscan II best fit sphere (BFS ) was obtained from an 8-mm-diameter area like the Galilei system does.
This study was analyzed with descriptive statistics and an univariate analysis of variables (Galilei and Orbscan) was performed in order to calculate:
- The central tendency (mean , median) and confidence interval (CI)
-The distribution (normal distribution test: Kolmogorov-Smirnov test)
-The dispersion (Standard Deviation, SD)
To evaluate the differences in means between the two groups of gathered data (Galilei and Orbscan II) the t-test (parametric test) was used , with a level of significance of p<0.005.
92 eyes were examined with the two devices. Gender : 25 males / 67 females Ages 17 to 55 years old, mean: 32,77 years old (95% CI
30,57 - 34,96)
DX: Myopia 23% Myopic astigmatism 53,2% Hyperopia 11% Hyperopic astigmatism 7,5% Presbyopia 3,3 % Mixed astigmatism 2 % We excluded keratoconus and any keratoconus suspects identified
with the CLMI index from the Keratron Scout and the KPI from the Galilei .
SUBJECTS
RESULTS Anterior Best-fit Sphere Radii (raBFS)
The mean radius of the anterior best-fit sphere (raBFS) was:
7.84 +/- 0.23 mm (SD) (95% CI 7,795 -7,891)with the Galilei
7.84 +/- 0.23 mm (SD) (95% CI 7,791 -7,890) with the Orbscan II
p= 1,0
raB
FS
Rad
ii(m
m)
8,6
8,4
8,2
8,0
7,8
7,6
7,4
ra BFS GAL ra BFS ORB II
The mean radius of the posterior best-fit sphere (rpBFS) was:
6.50 +/- 0.20 mm (SD) (95% CI 6,46 -6,54)with the Galilei
6.46 +/- 0.20 mm (SD) (95% CI 6,41 -6,50)with the Orbscan II
p=0,17.
RESULTS Posterior Best-fit Sphere Radii (rpBFS)
rpB
FS
Rad
ii(m
m)
7,0
6,9
6,8
6,7
6,6
6,5
6,4
6,3
6,2
6,1
rpBFS GAL rpBFS ORB II
Mean of the radius at the point of maximum anterior elevation
-1 3 6 10 13
70
60
50
40
30
20
10
0
rMEA GAL
Rel
ativ
e fr
eque
ncy
(%)
Sample size =92Lowest value =1,5Highest value = 12Mean = 5,61SD = 2,19
rMEA: mean of the radius at the point of maximum anterior elevation
-4 1 6 11 16
90
80
70
60
50
40
30
20
10
0
rMEA ORBSCAN II
Re
lativ
e f
req
ue
ncy
(%
)
Sample size = 92Lowest value = 2Highest value = 14Mean = 4,64SD = 2,23
The mean radius of the
maximum anterior elevation (rMEA) was :
5,61 +/- 2,19 µm (SD) (95% CI 5,16 – 6,07 ) with the Galilei 4,64 +/- 2,23 µm (SD), (95% CI 4,18 – 5,11) with the Orbscan II
p= 0,0023
RESULTS Radius of the Maximum Anterior Elevation (rMAE)
Mean of the radius at the point of maximum posterior elevation
2 6 9 13 17 20 24
45
40
35
30
25
20
15
10
5
0
rMEP GALILEI
Re
lativ
e f
req
ue
ncy
(%
)
Mean of the radius at the point of maximum posterior elevation
-10 -3 5 13 20 27 35
45
40
35
30
25
20
15
10
5
0
rMEP ORBSCAN II
Re
lativ
e f
req
ue
ncy
(%
)
Sample size = 92Lowest value = 5,50Highest value = 22,00Mean = 13,00SD = 3,35
Sample size = 92Lowest value = 1,00Highest value = 32,00Mean = 13,84SD= 6,65
The mean radius of the
maximum posterior elevation (rMPE) was:
13,0 +/- 3,35 µm (SD) (95% CI 12,31 – 13,69) with the Galilei
13,84 +/- 6,65 µm (SD), (95% CI 12,47 – 15,22) with the Orbscan II
p= 0,321
RESULTS Radius of the Maximum Posterior Elevation (rMPE)
Mean (error bars: 95% CI for mean)
620
600
580
560
540
520
500
480
460
GALILEICE
NT
RA
L C
OR
NE
AL
TH
ICK
NE
SS
GA
LIL
EI
Mean (error bars: 95% CI for mean)
650
600
550
500
450
ORBSCAN II
CE
NT
RA
L C
OR
NE
AL
TH
ICK
NE
SS
OR
BS
CA
N I
I
RESULTS Central Corneal Thickness (CCT)
The Central Corneal Thickness (CCT) mean was:
549 +/- 29.96 microns (SD)
(95% CI 542 – 555) with the Galilei, Lowest 474 highest 612
551 +/- 38.52 microns(SD)
(95% CI 543 – 559)with the OrbscanIILowest 459 highest 644
p=0,722
RESULTS Corneal Thinnest Point CTP
Corneal Thinnest Point mean CTP was :
546 +/- 29.6 microns(SD)(95% CI 540 – 552) with the Galilei
Lowest 472 highest 611
543 +/- 37.8 microns (SD)(95% CI 535 –551) with the Orbscan II
p=0,59.
TH
INN
ES
T P
AC
HY
ME
TR
Y (
mic
ron
s)
700
650
600
550
500
450
400
THINNEST GAL THINNEST ORB II
Conclusion:
There were a statistical difference between the
two devices in the maximun anterior elevation with a better normal tendency of the measurements in the Galilei results.
The pachymetry analysis shows a higher dispersion of the data for the Orbscan II ; due to a SD of 38.52 microns(µ) for the Orbscan II and 29.96 µ for the Galilei in the CCT and 37.8 µ for the Orbscan II and 29.6 µ for the Galilei in the CTP.
Conclusion: Even though both devices have different
centering systems, most of the elevation and pachymetry mean results did not show significant differences.
It is important to know the elevation and pachymetry variables in normal corneas, and their distribution to establish the clinical cut off with the Galilei dual-scheimpflug analyzer.
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