Aspherical ablation profiles in excimer laser treatments International Vision Correction Research Centre E-mail: angela.ehmer@med.uni-heidelberg.de Aspherical ablation profiles in excimer laser treatments Ehmer, MSc, M.P. Holzer, MD G.U. Auffarth, MD Ladies and Gentlemen when we are talking about laser treatments we have to think about the optimal ablation profile Dept. of Ophthalmology Ruprecht-Karls-University Heidelberg Chairman: H.E.Völcker, MD The authors have no financial interests in any of the products mentioned.

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) First some information for the background. As you all know the corneal shape don’t has a spherical curvature, its more similar to a prolate ellipse, in the picture marked as blue line. The diameter in the periphery is greater than at the apex. Q > 0  ellipsoid with the major axis in the X-Y plane Q = 0  sphere -1 < Q < 0  ellipsoid with the major axis in the Z direction Q = -1  paraboloid with the axis along the Z axis Q < -1  hyperboloid Angela Ehmer 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 The purpose of our study was to analyze the shape of the cornea to get knowledge about the changes of asphericity after laser treatment Angela Ehmer

Results LASEK 12 male (100%), 0 female treatment LASIK LASEK n Range number of eyes 48 12 age 35.29 ± 7.72 27 ± 6.61 years LASEK 12 male (100%), 0 female LASIK 20 male (41.67%), 28 female (58.33) refraction SE < 5 24 - 3.12 ± 1.18 12 -2.75 ± 1.40 D > 5 - 5.34 ± 2.64 In 48 eyes a Lasik was performed, exactly 24 of these eyes had a a spherical equivalent of less than 5 dpt, the remaining 24 eyes had more than 5 dpt. In 12 eyes a Lasek was done, all of them had a spherical equivalent less than 5 dpt. Angela Ehmer

Comparison outcome: LASIK < 5 D vs. LASIK > 5 D Mean Q- value (Qm) for LASIK > 5 D Mean Q- value (Qm) for LASIK < 5 D Mean Q value is calculated with Qflat and Qsteep of each eye In the first part lasik eyes with more vs. less than 5 dpt were compared Uncorrected post op visual acuity Angela Ehmer

Qm-Value and Spherical Aberrations Comparison outcome LASIK < 5 D vs. LASIK > 5 D Qm-Value and Spherical Aberrations In this graphic Qm value and Spherical aberrations pre and postoperative are shown. With reducing the refraction with an aspheric laser treatment the spherical Aberrations should be stable pre and postoperative. Here in this case the SA change as well as the Qm value for lasik eyes > 5dpt. An explanation for that can be the Flaplift one the one hand or the value of ablation on the other hand. * significant differences between the two groups (Wilcoxon, p< 0.05) Angela Ehmer

Comparison of outcome LASEK vs. LASIK < 5 D -1.5 -1 -0.5 0.5 1 1.5 2 Qm Pre Qm 3 Qm 6 Qm 12 -1.5 -1 -0.5 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 In part two the results of the different treatments, lasik< 5dpt and lasek were analyzed Uncorrected post op Visual acuity Angela Ehmer

Qm-Value and Spherical Aberrations Comparison of outcome LASEK vs. LASIK < 5 D Qm-Value and Spherical Aberrations * -0.2 0.2 0.4 0.6 0.8 1 1.2 Qm SA LASIK < 5dpt LASEK µm pre post Looking at the changes of Qvalue and spherical Abberations pre and postoperatively there was no change found with the spherical aberrations.Agianst this the Q value increased to a more positive value in both groups. A significant difference was found for the lasek group * significant differences between the two groups (Wilcoxon, p< 0.05) Angela Ehmer

LASIK < 5 D vs. LASIK >5 D 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 correlation between visual acuity and Q- value In conclusion we can say that in both groups there was no statistical significant difference in visual acuity. No correlations between q value and visual acuity were found. Good correlations were found with spherical aberrations and q value in all eyes measured 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 It is remarkable that in all groups a more positive Q value shows visual acuity of 20/20 and better. Therefore we can say that the Qvalue does not necessarily describe visual outcome. We need you to remember that Q is the geometric difference of spherical and aspherical shape. Regarding this the question remains open if we rather should use spherical aberrations than Q value as ideal target. Angela Ehmer

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 Certified for DIN EN ISO 9001:2000 Web: www.lasik-hd.de