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.