e-mail: angela.ehmer@med.uni-heidelberg.de

E-mail: angela.ehmer@med.uni-heidelberg.de

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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