1. Augenabteilung am St. Franziskus Hospital Münster Lasik Flap Thickness using the Zyoptix XP Microkeratome Susanne Stottmeister, Suphi Taneri * * Travel grant by Bausch & Lomb ASCRS Symposium, April 4-9, 2008, Chicago

2. Augenabteilung am St. Franziskus Hospital Münster Purpose To evaluate predictability and possible factors affecting flap thickness in laser in situ keratomileusis (LASIK) using the Zyoptix XP microkeratome.

3. Augenabteilung am St. Franziskus Hospital Münster Methods 250 primary LASIK Flaps created using 3 different B&L Zyoptix XP microkeratomes were evaluated. Elements with different Serial Numbers were combined. Ultrasound subtraction pachymetry was used to determine intraoperative flap thickness. © B&L

4. Augenabteilung am St. Franziskus Hospital Münster Methods II Each keratome cut was performed with a new blade in a 120µm or a 140µm head coupled to a 8.5 mm or 9.5 mm suction ring with 19 or 20 mm outer diameter. Head (µm) Suction ring (mm) Central Corneal Thickness (µm) mean ± SD (range) Patient Age (years) mean (range) 120 8.5/19561 ± 27 (531-599)37 (24-46) 8.5/20570 ± 25 (539-599)40 (24-47) 9.5/19546 ± 11 (534-560)43 (38-46) 9.5/20547 ± 31 (485-632)39 (21-67) 140 8.5/20578 ± 40 (532-601)41 (26-65) 9.5/20554 ± 45 (480-617)39 (21-65)

5. Augenabteilung am St. Franziskus Hospital Münster Results Measured intraoperative flap thickness was lower than labelled. Flap thickness in safe range Head (µm) nMean ±SD (µm) Range (µm) 120231110 ± 2270 - 167 14019124 ± 2586 - 160

6. Augenabteilung am St. Franziskus Hospital Münster Flap Thickness vs. Different Head/Ring Combinations Standard Deviation in most used Head/Ring combination was 22 µm Head (µm) Ring (mm) n Flap Thickness Mean ± SD (µm) 120 8.5/19 8.5/20 9.5/19 9.5/20 6 4 215 107 108 116 ± 22 140 8.5/20 9.5/20 5 14 136 112 ± 20

7. Augenabteilung am St. Franziskus Hospital Münster Corneal factors affecting Flap Thickness Keratometry showed no influence.

8. Augenabteilung am St. Franziskus Hospital Münster Corneal factors affecting Flap Thickness Flap thickness was not correlated to central corneal pachymetry.

9. Augenabteilung am St. Franziskus Hospital Münster Patient factors affecting Flap Thickness Age showed no influence.

10. Augenabteilung am St. Franziskus Hospital Münster Difference between 1 st and 2 nd Eye MW0.2 µm Min-47 µm Max50 µm SD22.5 µm Intrapatient Comparison Bilateral cuts with the same head size (120 µm or 140 µm, respectively) and different blades showed no dependance.

11. Augenabteilung am St. Franziskus Hospital Münster Comparison XP vs. Hansatome Head size (µm) Flap Thickness Mean ± SD (µm) Range (µm) n 16097 ± 1865 -16389 180111 ± 2061 -177128 200131 ± 2089 -16221 Head size (µm) Flap Thickness Mean ± SD (µm) Range (µm) n 120110 ± 2270 -167231 140124 ± 2586 -16019 XPHansatome A similar predictability of the Zyoptix XP microkeratome compared to the predecessor model (Hansatome) was observed.

12. Augenabteilung am St. Franziskus Hospital Münster Conclusions All flap thicknesses were in the safe range. Heads and rings of different sets were practically interchangeable. Factors affecting flap thickness seem to be more device-dependant than patient-related, thus obtaining flap thickness in the first eye did not enable predictions of the flap thickness in the partner eye.