1. Young Joo Shin, 1 Sang Mok Lee, 2 Jin Choi, 3 Eun Ryung Han, 4 Dong Hae Kim 4 1 H ally m University Gangnam Sacred Heart Hospital 2 3The Armed Forces Medical Command 3 Department of Ophthalmology, Seoul National University College of Medicine 4 Myung Dong St. Mary’s Eye Center

2. We conducted a retrospective analysis of laser refractive corneal surgery including LASIK and LASEK to evaluate the risk factors for retreatment using survival analysis for long-term results.

3. Study Population –This study was a retrospective analysis of the records of all patients who underwent laser refractive corneal surgery from 1999 to 2008. –Routine preoperative : UCVA, BSCVA, MR and CR, refraction, slit-lamp biomicroscope, IOP, corneal topography, keratometry, corneal thickness, indirect ophthalmoscopy and a screening visual field test –Postoperative refractive status (SE) and IOP were evaluated at 1 and 3 month postoperatively. –In the cases of retreatment, pre-operative ophthalmic examination includes SE, keratometry, IOP and corneal thickness. SE and IOP were evaluated at 1 and 3 month post-reoperatively –Subjects were divided into three groups by level of refractive correction. Group 1 had low myopia (SE < -3.00D) group2 moderate myopia (-3.00D ≤ SE <-6.00D) group 3 high myopia (SE ≤ -6.00D)

4. Surgical Technique –Surgery was performed under topical anesthesia (3 drops of proparacaine 0.5% at 5-minute intervals). Both the initial and retreatment procedures were performed by the same experienced surgeon (D. H. K). Retreatment technique –Retreatment was performed in patients who had residual refractive error of more than -1.00D (SE) and complain of subjective symptoms after laser refractive corneal surgery. Every patient had at least two successive refractions at 1-month intervals before re-treatment to ensure stable refraction. LASIK treatment was performed when the estimated residual stromal tissue after laser ablation was 250 mm or more. –Surgical procedures for retreatment were done as follows. All re-treatments in patients who underwent LASIK and need retreatment were done by lifting the flap. All re-treatments in patients who underwent LASEK and need retreatment were done by the same as primary LASEK procedure. –Patients were seen on the first postoperative day, and then at 1, 3, 6, 12 months and every year after refractive surgery, and all measurements recorded.

5. The mean age at surgery: 28.4 ± 6.3 years, (18 to 54 years). M:F = 2137 eyes:7164 eyes. Mean SE : -2.99 ± 1.44 D. SE –in men (-2.98 ± 1.51 D) = women (-2.98 ± 1.42 D; p = 0.691, t-test). –LASIK (-2.94 ± 1.39 D) < LASEK (-3.68 ± 1.61 D; p < 0.000, t-test). no relationship –between surgical procedure and gender (p = 0.074, Chi square test) –between laser type and surgical procedure (p = 0.331, Chi square test). The number of patients who underwent retreatment: 136 (1.5%).

6. Kaplan-Meier survival analysis the rate of retreatment in the Technolas group was significantly higher than that in the VISX group (p < 0.0001, Mantel-Cox log rank test) the rate of retreatment in the high myopic group (group 3: > -6D) was significantly higher than that in the low myopic group (p < 0.0001, Mantel-Cox log rank test)

7. Kaplan-Meier survival analysis the rate of retreatment in LASEK group was significantly higher than that in LASIK group (p = 0.006, Mantel-Cox log rank test) the rate of retreatment in male was significantly higher than that in female (p = 0.046, Mantel-Cox log rank test)

8. Cox regression analysis showed –only the rate of retreatment in Technolas group and high myopic group was significantly higher (p < 0.0001 and p < 0.0001, respectively), –not in male and in LASEK (p = 0.521 and 0.749, respectively)

9. The survival curve in right eye was not different from that in left eye (p = 0.731, Mantel-Cox log rank tes Kaplan-Meier survival plots of the three groups for eyes not requiring retreatment after corneal refractive surgery. Their survival curves were not significantly different (p = 0.202, Mantel-Cox log rank test).

10. SEs of patients who underwent LASEK were not different compared to LASIK (p = 0.125, Mann-Whitney test) and SEs of patient treated with Technolas was better compared to VISX (p < 0.0001, Mann-Whitney test) immediately after retreatments. Three months after retreatment, SEs in patients who underwent LASIK (-0.54 ± 0.63 D) were more targeted compared to LASEK (-1.05 ± 0.51 D; p = 0.001, Mann- Whitney test) and SEs in patients treated with Technolas (- 0.48 ± 0.52 D) were better compared to VISX (-1.10 ± 0.72 D; p < 0.0001, Mann-Whitney test). Corneal thickness increased after first corneal laser refractive surgery (Table 1). Real remnant corneal thickness (457.75 ± 29.91) was thicker compared predicted corneal thickness (436.79 ± 28.10) (p = 0.000, Mann-Whitney test).

11. TotalLASIKLASEKTechnolasVISX Interval btw primary surgery and retreatment 18.11 ± 14.2717.58 ± 14.5620.24 ± 13.115.56 ± 13.2624.44 ± 14.87 preop SE (D)-6.259 ± 2.16-5.98 ± 2.16-7.48 ± 1.72-5.58 ± 1.89-8.08 ± 1.72 Mean K (D)43.71 ± 1.3543.61 ± 1.3544.05 ± 1.3346.55 ± 1.2443.52 ± 1.60 IOP (mmHg)16.16 ± 2.7916.37 ± 2.8915.35 ± 2.2716.66 ± 2.7214.81 ± 2.59 Pachymetry (µm)525.20 ± 27.60533.15 ± 23.49491.70 ± 15.30531.88 ± 24.87507.32 ± 26.38 Corneal ablation during operation (µm) 88.41 ± 17.3889.05 ± 18.5185.52 ± 11.7790.21 ± 17.3483.58 ± 16.81 Postop 1 month SE (D)-0.87 ± 0.61-0.91 ± 0.56-0.75 ± 0.78-0.91 ± 0.56-0.79 ± 0.73 IOP (mmHg)11.73 ± 3.6811.86 ± 3.8811.21 ± 2.7812.21 ± 3.9010.48 ± 2.75 Mean K (D)39.52 ± 2.1339.69 ± 2.1738.94 ± 1.9140.09 ± 1.9238.08 ± 1.99 Postop 3 months SE (D)-1.67 ± 0.72-1.06 ± 0.73-1.58 ± 0.54-1.00 ± 0.71-1.61 ± 0.58 IOP (mmHg)9.92 ± 2.309.83 ± 2.3310. 30 ± 2.1510.06 ± 2.279.52 ± 2.35 Retreatment (µm) SE (D)-1.17 ± 0.722-1.12 ± 0.77-1.43 ± 0.41-1.12 ± 0.69-1.34 ± 0.78 IOP (mmHg)10.78 ± 2.2210.99 ± 2.1410.00 ± 2.4110.98 ± 2.1710.26 ± 2.31 Mean K (D)39.78 ± 1.5939.80 ± 1.7039.70 ± 1.0940.17 ± 1.4538.76 ± 1.53 Real CT by ultrasound pachymetry (µm) 457.75 ± 29.91465.64 ± 27.35424.83 ± 12.22463.98 ± 29.74441.07 ± 23.32 Corneal ablation during retreatment (um) 22.76 ± 6.5022.49 ± 6.4324.17 ± 6.7621.43 ± 5.4926.32 ± 7.56 Post-reop 1 month SE (D)-0.47 ± 0.62-0.43 ± 0.57-0.70 ± 0.78-0.39 ± 0.51-0.71 ± 0.79 IOP (mmHg)10.54 ± 2.6110.88 ± 2.609.22 ± 2.2611.16 ± 2.278.90 ± 2.80 Post-reop 3 month SE (D)-0.65 ± 0.64-0.54 ± 0.63-1.05 ± 0.51-0.48 ± 0.52-1.10 ± 0.72 IOP (mmHg)9.69 ± 2.209.53 ± 2.0210.43 ± 2.719.86 ± 2.219.27 ± 2.19 Predeicted CT (preop CT- ablation during operation 436.79 ± 28.10444.10 ± 25.42406.17 ± 14.68441.66 ± 27.11423.74 ± 26.55 Real CT at reoperation – predicted CT 20.97 ± 11.0121.54 ± 11.3618.65 ± 9.3422.31 ± 10.7017.32 ± 11.21

12. Higher spherical equivalent, and excimer laser system was found to be a predictor of retreatment after laser corneal refractive surgery. Retreatment was safe and effective for correcting undercorrection and regression.