1. Comparison of Varying the Ablation Diameter in LASIK and LASEK:The Effects on Anterior Chamber Depth (ACD) and Regression at 3 months Minoru Tomita, MD, PhD, Tadayuki Nakamura, MD, Minoru Tomita, MD, PhD, Tadayuki Nakamura, MD, Nobuo Nakamura, MD, PhD, Tadahiko Tsuru, MD, PhD Shinagawa Lasik Center, Tokyo, Japan Shinagawa Lasik Center, Tokyo, Japan Shinagawa LASIK Center

2. Purpose LASIK using Femtosecond Laser (FS laser) has been widely performed all over the world. In this study, we evaluated the changes in anterior chamber depth (ACD) after LASIK and LASEK operations by varying the ablation diameter. We have also examined for comparison if there is any correlation between the ACD change and the regression after LASIK and LASEK operations and by the degree of refractive error. Shinagawa LASIK Center

3. Subjects and Methods: 559 eyes of 280 patients were selected randomly from procedures of IntraLASIK ( IntraLASIK:Laser Assisted in situ Keratomileusis using IntraLase FS60® laser ( Abbot Medical Optics Inc.) with Allegretto® (WaveLight Inc.) and LASEK (Laser Assisted in situ Keratomileusis) conducted between July 2007 and May 2008. Patients were separated into four groups by diameter of the ablative region, either 6.0mm or 6.5mm and also by procedure, either LASIK or LASEK (Table 1 and 2). The results were measured by Orbscan II® (Bausch&Lomb) for preoperative and postoperative 3 months (Table 3). The comparison for ACD change by ablative zone in LASIK and LASEK and its correlation with regression were examined.

4. Shinagawa LASIK Center All the statistics were analyzed using StatView 5.0 for Windows (SAS Institute, Inc). Result were considered statistically significant if the P value was less than 0.05.

5. Table 1 - Group by Category Procedure Ablation Zone Number of People Number of Eyes Patient Age Mean±SD Group I IntraLASIK6.0mm7915833.11±7.95 Group II IntraLASIK6.5mm9118131.78±6.49 Group III LASEK6.0mm326430.13±5.48 Group IV LASEK6.5mm7815631.32±7.07 Shinagawa LASIK Center

6. Preoperative Mean UCVA Mean BSCVA SE Mean±SD Group I 0.04 （ 20/500) 1.55 (20/13)-7.40D±2.02 Group II0.10 (20/200)1.62 (20/12.5)-4.28D±2.01 Group III 0.05 (20/400)1.62 (20/12.5)-6.16D±1.50 Group IV0.07 (20/285)1.63 (20/12.5)-4.49D±1.90 Table 2 – Preoperative Data

7. Shinagawa LASIK Center Table 3 - Postoperative Data at 3 Months 3Ｍ3Ｍ Mean UCVA Mean BSCVA SE Mean±SD ACD Change (μm) Safety Index Efficacy Index Group I 1.49 （ 20/13) 1.58 (20/13) +0.16D±0.3224.431.020.97 Group II 1.58 (20/13) 1.65 (20/12) +0.11D±0.2938.121.010.98 Group III 1.48 (20/13) 1.57 (20/13) +0.33D±0.4362.810.970.91 Group IV 1.47 (20/14) 1.52 (20/13) +0.16D±0.3846.600.950.92

8. A significant difference was observed in preoperative and postoperative ACD change in group I and III (t-test:P<0.05) and no significant differences were observed for the rest of the groups. As for the correlation between refractive errors and regression after 3 months, significant differences were noted when comparing the results of group I to group II and also when comparing group III and group IV (Table 3). However, no significant differences were found for ACD change in group I to group II and also group III and group IV (t-test:P>0.05). Result: Shinagawa LASIK Center

9. Discussions Ablation diameter of 6.0mm recognized significant differences on mild regression at 3 month than 6.5mm in both IntraLASIK and LASEK. However, there were no significant differences observed in ACD change for 6.5mm diameter IntraLASIK and LASEK but 6.0mm diameter for IntraLASIK and LASEK recognized significant differences. Ablation diameter of 6.0mm recognized significant differences on mild regression at 3 month than 6.5mm in both IntraLASIK and LASEK. However, there were no significant differences observed in ACD change for 6.5mm diameter IntraLASIK and LASEK but 6.0mm diameter for IntraLASIK and LASEK recognized significant differences.

10. Summary 1.Changing the diameter of ablative zone did not result in any significant difference on ACD in either IntraLASIK or LASEK. 2. Ablation diameter of 6.0mm seems to have more regression compared to 6.5mm. Shinagawa LASIK Center