1. Comparative Evaluation of Photorefractive Keratectomy With Use of Excimer Laser and Solid-State Laser System G. A. Kontadakis; G. A. Kounis; G. D. Kymionis; A. Stratos; I. G. Pallikaris Institute of Vision and Optics, University of Crete, Heraklion Crete, Greece. The authors have no financial interest in the subject matter of this poster.

2. introduction Solid state laser technology was introduced in refractive surgery as an alternative to the excimer laser. The gain medium in these devices is Nd:YAG crystals that generate beam of 1064nm. The radiation that is produced by transmitting the 1064nm beam throw a setting of non linear crystals has a wavelength of 213nm. It has been proved to be suitable for corneal ablation and also to have similar ablation profile with the 193nm pulsed radiation. The main benefit of the 213 nm wavelength beam is that it less absorbed by salt solutions and therefore the ablation rate is probably less dependent on corneal hydration during surgery. Purpose : To compare refractive results of photorefractive keratectomy (PRK) with the Solid State laser and Excimer laser.

3. Methods This retrospective cohort study comprised 82 patients (147 eyes) who received PRK with the excimer laser Allegretto 400 Wave Eye-Q (group 1), and 73 (145 eyes) who received PRK with the solid state laser Pulzar Z1 (group 2). All patients had a complete ophthalmic examination preoperatively to exclude ocular disease. All procedures were performed by the same surgeon (I.G.P.) using an identical technique. Preoperative and postoperative assessments included: uncorrected distance visual acuity (UDVA), corrected distance VA (CDVA), manifest and cycloplegic refractions, slit lamp examination and corneal topography. Normality of distribution of continuous variables were assessed with the Kolmogorov-Smirnov test. Variables with normal distribution were compared with independent samples t-test. When distribution was not normal Mann-Whitney test was used to asses the differences.

4. Methods (2) Patient demographics: Patients (Eyes) Mean Age Age Range Sex (F/M) Customvis Pulzar Z1 73 (145) 34.1±8.5 [56-21] (42/31) Wavelight Allegretto 400 82 (147) 31.9±6.1 [50-21] (52/30) Treatment Category EyesMean Age Mean mmc Time(sec) EyesMean Age Mean mmc Time(sec) Low Myopia 0 to -3D SEQ 4034.4±9.74.1±5.641 31.9±4.8(p =0.57) 6.3±4.3 Moderate Myopia -3 to -6D SEQ 8733.5±7.810.1±8.28731.8±5.912.8±5.6 High Myopia -6D to -12D SEQ 1835.1±9.020.6±8.11933.7±8.823.8±6.5 SEQ: sherical equivalent; mean mmc time is the mean time of intraoperative Mitomycin C application. All parameters did not show statistically significant differences between the groups.

5. Results: Postop results for Customvis Pulzar Z1 3 Months PostOp12 Months PostOp Low Myopia > - 3.0D Moderate Myopia -6.0 < ≤ -3.0D High Myopia ≤ -6.0D Low Myopia > - 3.0D Moderate Myopia -6.0 < ≤ -3.0D High Myopia ≤ -6.0D Rem SEQ† 0.02±0.52-0.07±0.630.31±0.970.01±0.52-0.11±0.650.24±0.77 Mean Rem Refraction† 0.16/-0.28@178° 0.10/- 0.35@174° 0.6/-0.58@2°0.25/-0.48@13° 0.04/- 0.31@180° 0.46/- 0.43@15° LogMar CDVA‡ -0.05±0.05-0.04±0.04-0.01±0.09-0.06±0.04-0.05±0.06-0.05±0.12 LogMar UDVA‡ -0.02±0.10.01±0.080.08±0.14-0.03±0.050±0.10.05±0.11 Postop results for Wavelight Allegretto 400 3 Months PostOp12 Months PostOp Low Myopia > - 3.0D Moderate Myopia -6.0 < ≤ -3.0D High Myopia ≤ - 6.0D Low Myopia > - 3.0D Moderate Myopia -6.0 < ≤ -3.0D High Myopia ≤ - 6.0D Rem SEQ† 0.12±0.460.37±0.610.87±0.65-0.04±0.470.32±0.510.29±0.42 Mean Rem Refraction† 0.17/-0.11@170°0.44/-0.13@7°0.99/-0.24@178° -0.03/- 0.02@21° 0.42/- 0.21@175° 0.41/-0.25@43° LogMar CDVA‡ -0.07±0.07-0.05±0.070.03±0.11-0.06±0.07-0.07±0.07-0.05±0.05 LogMar UDVA‡ -0.05±0.08-0.03±0.080.04±0.13-0.01±0.12-0.03±0.11-0.02±0.09 Rem SEQ: (attempted correction)-(achieved correction) in spherical equivalent Differences between parameters in corresponding laser groups were not statistically significant

6. Results: safety Solid state laser Excimer laser Both laser platforms performed similarly in terms of safety of the procedure

7. Results: predictability Procedures performed with both laser platforms performed demonstrated satisfying predictability Solid state laser Excimer laser

8. Results: stability Refractive results showed similar stability after procedures performed with both laser platforms

9. Conclusions: Both systems performed similarly in terms of safety, efficacy and predictability. The use of the Solid State laser for the correction of myopia with photorefractive keratectomy is an effective alternative for the Excimer laser.