Ik Hee Ryu , Hun Yang, David S. Kang, Jin Kuk Kim BS Clean Vision Eye center

1. Comparison of the Topographic Optical Zone After LASIK for Myopic Astigmatism With 2 Excimer Laser Platforms IkHeeRyu, Hun Yang, David S. Kang, Jin Kuk Kim BS Clean Vision Eye center The authors have no financial interest in the subject matter of this e-poster.

2. By technical advance in excimer laser platform, programmed ablation zone gains it’s maximal boundary • Night vision symptoms such as halo and glare due to larger scopotic pupil in relation of ablated corneal optical zone being dramatically decreased • Different manufacturer produce a variety of laser platforms, yielding various degree of effective optical zone zone under identical ablation zone and parameters • Several papers previously reported a difference between intended ablation zone and actual effective optical zone regardless of excimer laser platforms

3. Purpose • In our study • Two types of excimer laser : Allegretto-Q 400 Hz & SchwindAmaris being used • Comparison after laser refractive surgery in ablation parameters (short & long axis, ablation area) between two platforms • Investigating preoperative parameters relation to postoperative optical zone

4. Patients & Methods • Between Feb. to Mar., 2010, 99 patients (198 eyes) with femtosecond laser-assisted LASIK enrolled; retropective study undergone • Allegretto group: 50 patients (100 eyes) • Amaris group : 49 patients(98 eyes) • Identical programmed ablation zone of 6.5 mm applied to all cases of LASIK regardless of laser platforms • After certain period of time (mean: 19.4 days), topographic measurements performed • Short and long axis of optical zone identified on the topography were measured • Area of optical zonewas calculated via short/long axis

5. Measurement of optical zone • Short and long axis identified as an imaginary line connecting the boundary margin at least 1 diopter difference from the center • Optical zone being elliptical in all cases, short and long axis can be identified • Area of Optical zone • Area= ∏ × long axis× short axis/4 • Contributing factors • Investigate to identify statistical correlation between optical zone and preoperative sphere, cylinder, sphere-cylinder ratio, keratometric value (K1, K2, mean K) • Statistical comparison by spearman correlation (SPSS 12.0 ver.)

6. Short axis Long axis

7. Results *: statistically significant

8. Allegretto group Amaris group Pre: preoperative; sph: spherical; cyl: cylinder; SE: spherical equivalent; SC: sphero-cylinder ratio; K1: lower K value; K2: higer K value red blanks: statistically significant

9. Conclusions • Topographical optical zone • Diameters (long and short axis) • A statistical significance in Allegretto group • In short and long axis, longer diameter observed • Calculated area of optical zone • Larger in Allegretto group, but not statistically significant • No linear correlation between preoperative parameters and optical zone in both diameters and calculated area regardless of laser platforms

10. Allegrettogroup • Correlation with diameters (long/short axis) • Preoperative spherical/cylindrical amount, sphero-cylinder ratio affecting long axis • Correlation with area • Preoperative sphero-cylindrical ratio affects caculated area of optical zone • Amarisgroup • Correlation with diameters (long/short axis) • Preoperative spherical/cylindrical amount, spherical equivalent, sphero-cylinder ratio and flatter K-value affecting long axis • Correlation with area • Preoperative spherical amount, spherical equivalent and faltter K-value affects caculated area of optical zone

11. Under the identical circumstances, different optical zone in diameters and area was observed with different types of laser platforms • To reduce night vision complaints such as glare and halo, preoperative refractive errors, pupil size, corneal thickness and keratometric value must be considered for selecting a proper laser platform and ablation zone