1. Professor Ioannis Pallikaris MD, PhD

2.  Different mediums (Nd:YAG Crystals vs ArF Gas)  Less optics for the shaping of the pulse  No use of toxic gasses  Improved beam quality and shape  Reduced thermal effect and collateral damage  Hydration dependence on 193nm

3.  Corrosive, toxic and high cost gases  Big spot size  Absorption coefficient suggest 193nm affected more by BSS or NaCl 0.9%

4. Mirror 90% Medium Pumping ArF 193 nm@400hz Mirror 100% Medium Nd:YAG 1064 nm 213 nm@300Hz Non-linear optics

5.  All treatments performed by CustomVis Pulzar Z1 & Allegretto 400  Last follow-up to 12 months  PRK Mean SEQ = - 4.50 ± 1.81D  [-6.50D to -1.50D Sph and up to –2.50D Cyl]  160 eyes in Excimer and 160 in Solid  MMC solution was applied to PRK cases in both systems according to given attempted correction LASIK and PRK for treating Myopia and Myopic Astigmatism. A retrospective study.

6.  89% between + 1.00/-1.00 D at 12 months postop for Excimer  96% between +1.00/-1.00 D at 12 months postop for Solid

7.  35% of eyes gained more than 1 line in Solid  31% of eyes gained more than 1 line in Eximer 157 eyes

8.  0% of eyes changed more than 0.50D between 3m and last postop Solid

9. Smooth ablation surface No edema or distortion of the adjacent corneal stroma Normal structure of the endothelial layer in both groups S E S EE S

10.  The Descemet’s membrane and the endothelium did not demonstrate any morphological difference with intact tissues S E S E Solid Excimer S E

11.  No statistical significant difference found between two groups in any postoperative interval ( p >0.05). Study group, 30 eyes underwent myopic PRK with the CustomVis Pulzar Z1 laser system. Control group, 30 eyes underwent myopic PRK with the a Allegretto Wavelight 400Hz Excimer system

12.  Coma Y Decrease 0.04  Coma X Increase 0.05  Spherical aberration Increase 0.04  HO rms Increase 0.08

13. Alcon LADARVision4000 System Wavefront-guided Excimer Laser Ablation Using PRK Mean attSphEq : -4.21D Diopters 6months postop :Pupil diameter 6mm RMS HO: decrease 0.29 Spherical Aberration: decrease 0.06 Third order RMS: increase 0.13 Daniel S. Durrie,, et al JRS 2008 WaveLight ALLEGRETTO Laser Wavefront Optimized Treatments in Surface Ablation Mean attSphEq : -3.64 ±1.92 Diopters 3months postop:Pupil diameter 6mm RMS HO: increase 0.03 Spherical Aberration: increase 0.01 Third order RMS: increase 0.03 Aleksandar Stojanovic, et al JRS 2008

14.  Predictability presented similar results between the two systems  The excimer seems to give more overcorrection effect due to the use of MMC compared to the Solid system  Both system are safe for correction with PRK and LASIK  Stability of refraction is the same for both systems with stability level being equal at 12 moths PostOp period

15.  Histology has proved to have similar results to the samples of Excimer laser  There are no statistical significant changes in corneal endothelium monolayer in post PRK patients (up to one year) with solid state (213 nm) and excimer (193 nm) laser systems.  Similar changes to high order aberration were found between Solid and Excimer