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International Vision Correction Research Centre. E-mail: [email protected]. Aspherical ablation profiles in excimer laser treatments. Ehmer, MSc, M.P. Holzer, MD G.U. Auffarth, MD. The authors have no financial interests in any of the products mentioned. - PowerPoint PPT Presentation
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E-mail: [email protected]
A. Ehmer, MSc, M.P. Holzer, MD
G.U. Auffarth, MD
Dept. of OphthalmologyRuprecht-Karls-University Heidelberg
Chairman: H.E.Völcker, MD
The authors have no financial interests in any of the products
mentioned.
Aspherical ablation profiles in excimer laser treatments
International Vision Correction Research Centre
Angela Ehmer
Background – Aspheric profile of the cornea
• the curvature of the cornea in the periphery is less compared to the apex Shape of human cornea is no sphere
• Human cornea is comparable to prolate ellipse
• To specify the type of conicoid the parameter Q is used value for asphericity is Q
Variation in conicoid for different asphericities Q, but for the same value of radius R (Source: Kiely et al., 1982)
Q > 0 ellipsoid with the major axis in the X-Y planeQ = 0 sphere-1 < Q < 0 ellipsoid with the major axis in the Z directionQ = -1 paraboloid with the axis along the Z axisQ < -1 hyperboloid
Angela Ehmer
Purpose and Methods
Purpose
• Analysis of corneal shape following excimer laser treatment with an aspheric ablation profile
Methods• Preop
• Visual acuity, refraction, pachymetry, corneal topography, wavefront analysis, pupillometry
• Excimer laser treatment• Schwind ESIRIS; Wavefront optimized, aspheric• LASIK or LASEK
• Postop 3, 6, 12 months • Visual acuity, refraction, wavefront analysis• Minimum pupil size 6mm
Angela Ehmer
Results
• LASEK 12 male (100%), 0 female
• LASIK 20 male (41.67%), 28 female (58.33)
treatment LASIK LASEK
n Range n Range
number of eyes 48 12
age 35.29 ± 7.72 27 ± 6.61 years
refraction SE
< 5 24 - 3.12 ± 1.18 12 -2.75 ± 1.40 D
> 5 24 - 5.34 ± 2.64 0 D
Angela Ehmer
Comparison outcome: LASIK < 5 D vs. LASIK > 5 D
-0,15-0,1
-0,050
0,050,1
0,150,2
0,250,3
0,35
sc 1d sc 3d sc 21d sc 3 mon sc 6 mon sc 12 mon
Vis
ual
acu
ity
Lo
gM
AR
LASIK > 5 D LASIK < 5 D
Uncorrected post op visual acuity
-2
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
3
3,5
Qm Pre Qm 3 Qm 6 Qm 12
Mean Q- value (Qm) for LASIK < 5 D
-2
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
3
3,5
Qm pre Qm 3 Qm 6 Qm 12
Mean Q- value (Qm) for LASIK > 5 D
Mean Q value is calculated with Qflat and Qsteep of each eye
Angela Ehmer
Qm-Value and Spherical Aberrations
* significant differences between the two groups (Wilcoxon, p< 0.05)
-0,2
0
0,2
0,4
0,6
0,8
1
1,2
µm
pre pre pre prepostpost
postpost
Qm QmSA SA
* *
LASIK < 5 D LASIK > 5 D
Comparison outcome LASIK < 5 D vs. LASIK > 5 D
Angela Ehmer
Comparison of outcome LASEK vs. LASIK < 5 D
-0,15
-0,1
-0,05
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
sc 1d sc 3d sc 21d sc 3 mon sc 6 mon sc 12 mon
Vis
ual
acu
ity
Lo
gM
AR
LASEK LASIK < 5 D
Uncorrected post op Visual acuity
-1.5
-1
-0.5
0
0.5
1
1.5
2
Qm Pre Qm 3 Qm 6 Qm 12
-1.5
-1
-0.5
0
0.5
1
1.5
2
Qm Pre Qm 3 Qm 6 Qm 12
Mean Q- value (Qm) for LASIK < 5 D Mean Q- value (Qm) for LASEK
Mean Q value is calculated with Qflat and Qsteep of each eye
Angela Ehmer
Qm-Value and Spherical Aberrations
* significant differences between the two groups (Wilcoxon, p< 0.05)
*
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
Qm QmSA SA
LASIK < 5dpt LASEKµm
pre post pre postpre post
pre post
*
Comparison of outcome LASEK vs. LASIK < 5 D
Angela Ehmer
Conclusions
LASIK < 5 D vs. LASIK >5 D– No statistical difference in visual acuity
– No correlation between visual acuity and Q value
– Good correlation between spherical aberrations
and Q- value
LASIK < 5 D vs. LASEK– No statistical difference in visual acuity
– No correlation between visual acuity and Q- value
– Good correlation between spherical aberrations
and Q- value
Angela Ehmer
Conclusions
Q value is a geometric difference of the spherical and the aspherical shape
Q-value in all groups is positive even though visual acuity is 20/20 and better
Change of dioptres and Q-value – no change in spherical aberrations
Spherical aberrations seems to be a more ideal target instead of Q value
G.U. Auffarth, MD, PhD
A. F. M. Borkenstein, MD
A. Ehmer, MSc
S. Hara, MD
M.P. Holzer, MD
H. Jin, MD
I.J. Limberger, MD
T.M. Rabsilber, MD
M.J. Sanchez,MD
I. Schmack, MD
Web: www.lasik-hd.de
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