1) Early LASIK ablation profiles for high myopia induced spherical aberration and night vision disturbances. 2) Newer aspheric and wavefront-guided profiles aim to reduce spherical aberration induction but may still cause issues for high corrections. 3) A two-stage procedure using wavefront-guided or topography-guided enhancement can improve outcomes for high myopia LASIK.

1. LASIK for high myopia: New considerations Dan Z Reinstein MD MA(Cantab) FRCSC FRCOphth 1,2,3,4 1. London Vision Clinic, London, UK 2. St. Thomas’ Hospital - Kings College, London, UK 3. Weill Medical College of Cornell University, New York, USA 4. Centre Hospitalier National d’Ophtalmologie, (Pr. Laroche) , Paris, France

2. First Results: Munnerlyn Ablation Profile Early ablation profiles often induced: Night Vision disturbances Decreased contrast sensitivity Limited the range of treatable refractions PROBLEM: Induction of spherical aberration Eur J Ophthalmol. 1994 Jan-Mar;4(1):43-51. Night vision after excimer laser photorefractive keratectomy: haze and halos. O'Brart DP, Lohmann CP, Fitzke FW, Smith SE, Kerr-Muir MG, Marshall J.

3. Ablation Profile Design: Larger Optical Zone Arch Ophthalmol. 1995 Apr;113(4):438-43. The effects of ablation diameter on the outcome of excimer laser photorefractive keratectomy. A prospective, randomized, double-blind study. O'Brart DP, Corbett MC, Lohmann CP, Kerr Muir MG, Marshall J. J Refract Corneal Surg. 1994 Mar-Apr;10(2):87-94. Excimer laser photorefractive keratectomy for myopia: comparison of 4.00- and 5.00-millimeter ablation zones. O'Brart DP, Gartry DS, Lohmann CP, Muir MG, Marshall J. Topography Wavefront Example: 5-mm Munnerlyn ablation for -6.00 D (1993 Summit Laser) Z(4,0) (OSA) 1.18 µm

4. Ablation Profile Design: Aspheric Profiles Barraquer 1980 Suggested parabolic keratomileusis Seiler 1993 – PRK aspheric profiles Less starburst & halos Larger effective clear optical zone size

5. Why was spherical aberration increasing?

6. Fluence correction: Topography Beam reflection compensation Beam projection compensation Optimization: Fluence correction J Refract Surg 2001;17(5):S584-7. Influence of corneal curvature on calculation of ablation patterns used in photorefractive laser surgery. Mrochen M, Seiler T.

7. Optimization Biomechanics VHF digital ultrasound

8. Artemis C12 Display Reinstein et al. Journal of Refractive Surgery 2000 Jul-Aug;16:414-30 Roberts C. The cornea is not a piece of plastic. JRS 2000; 16:407-413 VHF digital ultrasound

9. Examples of Peripheral Stromal Thickening Roberts C. The cornea is not a piece of plastic. Peripheral Stromal Thickening Central Flattening

10. Corneal Biomechanical Trade-off Hyperopic shift induced by Central flattening due to peripheral tissue removal Myopic shift induced by Epithelial thickening Bowing of the back surface Post-Op Pre-Op Back surface bowing Epithelial thickening

11. Free lunch?

12. ESCRS 2002, DZ Reinstein: Q-Slider

13. ESCRS 2002, DZ Reinstein: Q-Slider

14. ESCRS 2002, DZ Reinstein: Q-Slider

15. ESCRS 2002, DZ Reinstein: Q-Slider

16. ESCRS 2002, DZ Reinstein: Q-Slider

17. ESCRS 2002, DZ Reinstein: Q-Slider

18. Free Lunch? Increasing ablation zone diameter Adding asphericity Increases central ablation depth No “Free Lunch”

19. 550 µm Pachymetry: Forces Compromise Modern aspheric ablation profiles still induce spherical aberration Problem: high myopic corrections may result in NVDs

20. Wavefront-Guided Treatment of Spherical Aberration

21. How Effective are Wavefront Repair Treatments? Repair Group Complaining NVDs post LASIK Wavefront-Guided Repair Treatment Control Group Not Complaining NVDs post LASIK 16 eyes in study 4:1 matched for sphere & cyl Aberrations Pre-op Aberrations Post-op Compare Aberrations Aberrations Pre-repair Aberrations Post-repair

22. Correlation of Contrast with Wavefront Spherical Aberration Contrast Sensitivity

23. Correlation of Contrast with Wavefront Spherical Aberration Contrast Sensitivity 27% Gross Reduction 53% Net Reduction (cf tolerable level) Tolerable level ~0.56 µm @ 6mm

24. Pre-Compensate for Spherical Aberration “ Q-slider” (WaveLight) Wavefront-guided ablation Includes pre-op spherical aberration Effect dependent on pre-op spherical aberration Our Approach: Include an “artificial” wavefront Isolate spherical aberration: Z(4,0) as the only coefficient Z(4,0) coefficient proportional to expected induction Increase Z(4,0) coefficient: wavefront only 20% effective

25. Patient 1, OD -7.13 D Corrected 6mm OSA Coma 0.04 µm Sph Ab 0.42 µm HO RMS 0.52 µm 6mm OSA Coma 0.09 µm Sph Ab 0.48 µm HO RMS 0.59 µm

26. Patient 1, OS -9.00 D Corrected 6mm OSA Coma 0.03 µm Sph Ab 0.49 µm HO RMS 0.57 µm 6mm OSA Coma 0.05 µm Sph Ab 0.55 µm HO RMS 0.60 µm

27. Patient 1, Night Vision Pre Op Post Op Rx Treated OD -6.50 -1.25 x 178 OS -8.25 -1.50 x 17

28. Induction of Spherical Aberration Complaint of NVD post RS 1 1

29. Limits to SA Pre-Compensation Excess spherical aberration pre-compensation can lead to “central islands” TMS WASCA (zonal) Epithelium OD

30. CENTRAL ISLANDS: Slides courtesy Gordon Balazsi, MD -5.50 D ablation Diplopia first week Slow resolution over 2 weeks

31. CENTRAL ISLANDS: Slides courtesy Gordon Balazsi, MD -5.00 D ablation

32. Differences in Ablation Depth

33. Ablation Depth with SA Pre-Compensation Including extra wavefront increases ablation depth But, treatment of spherical aberration will also correct some sphere Unexpected Result: Greater over-correction than expected for larger Z(4,0) coefficients Consequence: Lower ablation depth than in theory

34. Ablation Depth with SA Pre-Compensation

35. New Profile for High Myopia Non-linear aspheric ablation profile: Increased peripheral ablation (not ↑ z(4,0)) Reduced induction of spherical aberration Free lunch: some myopia corrected due to central flattening Extend this concept further to promote central flattening Ability to correct high myopia without risk of NVDs

36. New Profile: “Free Lunch” Over-corrected by +0.50 D compared with theory Ablation depth lower than expected

37. Ablation Depth for New Profile

38. Femtosecond Lasers Femtosecond lasers have improved flap thickness reproducibility (VisuMax SD: 8 µm) We can create thinner flaps (VisuMax: 80 µm) Thinner flaps extends the range of myopia in LASIK Pre-release online

39. Outcomes

40. New Profile for High Myopia Patients Myopia SEQ -9.51 ± 1.32 D -8.00 up to -14.50 D Myopia max merid -10.18 ± 1.48 D -8.00 up to -16.00 D Cylinder -1.32 ± 1.10 D up to -6.25 D 220 eyes 1 year follow up Retreatments 45% eyes treated as “two-stage” Enhancement rate (non two-stage): 35%

41. Advantages of Two Stage Procedure Increased safety Greater RST for primary treatment Artemis measured RST to calculate retreatment Option to retreat using topography-guided profile More accurate result Patient has lower expectations

42. Topography Guided Retreatment Pre Post Reduced Sph Ab 0.48 µm 0.28 µm 41% HO RMS 0.72 µm 0.57 µm 21%

43. Example RST Planning Refraction -10.75 D sph Pachymetry 509 µm Flap Thickness (VisuMax) 80 µm Ablation Depth 135 µm Predicted RST 296 µm

44. MEL80 High Myopia: Accuracy

45. MEL80 High Myopia: Accuracy Within ±0.50 D 71% Within ±1.00 D 94%

46. Monocular Efficacy (excluding eyes not intended plano) n=176

47. n=176 98.3% Success Rate Pre Spectacle Corrected vs Post Uncorrected (excluding eyes not intended plano)

48. Pre Spectacle Corrected vs Post Uncorrected (excluding eyes not intended plano) n=176 41% Better Than Glasses

49. MEL80 High Myopia: Safety – BSCVA N=4 n=220

50. MEL80 High Myopia: Contrast Sensitivity * * Statistically significant (p<0.05)

51. Stability 3 Mo 6 Mo 12 Mo 24 Mo Pre-op 1 Day 1 Month 3 Months 6 Months 1 Year 2 Years Mean ±SD -9.60 ±1.39 +0.41 ±0.82 +0.01 ±0.82 -0.18 ±0.86 -0.22 ±0.91 -0.04 ±0.91 -0.06 ±1.07 # eyes 220 199 201 188 158 124 45

52. Take Home Message Know your spherical aberration induction per dioptre Measure pre-op spherical aberration Check whether spherical aberration is going to go beyond the threshold Use SA pre-compensation Use a 2-stage procedure (wavefront / topography guided repair if necessary as second treatment) Caution with predicted RST Reduce potential errors Measure pachymetry with high repeatability instrument Use high reproducibility flap creation technique Always include flap thickness bias

53. LASIK for high myopia: New considerations Dan Z Reinstein MD MA(Cantab) FRCSC FRCOphth 1,2,3,4 1. London Vision Clinic, London, UK 2. St. Thomas’ Hospital - Kings College, London, UK 3. Weill Medical College of Cornell University, New York, USA 4. Centre Hospitalier National d’Ophtalmologie, (Pr. Laroche) , Paris, France Thank You

54. Topography Guided Retreatment Pre Post Reduced Sph Ab 0.48 µm 0.28 µm 41% HO RMS 0.72 µm 0.57 µm 21%

55. Benefit of Aspheric-WF over Aspheric Spherical Aberration Z4,0 -50% -50% -50% -50%