1. Topography-Guided Photorefractive Keratectomy for Irregular Astigmatism following Penetrating Keratoplasty Johnson Tan, MBBS MRCSEd (Ophth) FRCSEd (Ophth) FAMS 1,2 Simon Holland, MD FRCSC 1,3 David TC Lin, MD FRCSC 3 1 University of British Columbia, Vancouver, Canada 2 National Healthcare Group Eye Institute, Singapore 3 Pacific Laser Eye Centre, Vancouver, Canada WCC, San Diego 2015

2. Financial Interest Holland, Simon: Alcon Laboratories Inc: Research Support Allergan and Bausch & Lomb: Travel Support The other authors have no financial interests in the materials mentioned

3. Purpose To evaluate the efficacy and safety of the custom Topographic Neutralization Technique (TNT) in Topography-Guided Photorefractive Keratectomy (TG PRK) in irregular astigmatism following Penetrating Keratoplasty (PK)

4. Methods Retrospective, non-randomized, consecutive, case series 49 eyes with irregular astigmatism after PK Topography-Guided Customized Ablation Treatment (T- CAT) planning software with ALLEGRETTO WAVE® (AW) Eye-Q Excimer laser platform (Alcon Laboratories Inc, Ft Worth, Texas) Custom Topography Neutralization Technique (TNT) adjust for the induced refractive change of surface regularization from topography-guided treatments

5. Procedure Trans-epithelial PTK, followed by TG PRK with T-CAT software and TNT Mitomycin-C 0.02% for 60-75 seconds Bandage contact lens fitted and remained in place until full re-epithelialization Fluoromethalone 0.12% eyedrops were given for 3 months, with a tapered dosing

6. Data Analysis At 3, 6 and 12 months Uncorrected Visual Acuity (UCVA) Best Corrected Visual Acuity (BCVA) Manifest Refraction (MR) Topographic Keratometry

7. Results 49 eyes had treatment; 23 eyes had follow up of at least 12 months UVA: 35% (8/23) achieved UVA ≥ 20/40 None had UVA ≥ 20/40 preoperatively BCVA: 48% (11/23) had improved BCVA 35% (8/23) gained 2 or more lines 17% (4/23) lost 1 line 4% (1/23) lost 2 or more lines

9. Results Manifest Cylinder: Pre-operative: 0.75D to 8.00D Post-operative: 0.00D to 6.00D Average improvement: 2.97D Average Spherical Equivalent improved by 1.45D, from -2.32D to -0.87D Topographic Cylinder: Pre-operative: 1.79D to 13.74D Average improvement: 2.89D of cylinder

11. Results Retreatment rate: 8.7% No cases of delayed epithelial healing No significant haze (<2)

13. TG-PRK for PK Pre-op13 Months Post-op UVA: 20/300UVA: 20/50 -2 MR: +4.00-6.00 x 005 20/80 -1 MR: pl-4.00 x 175 20/40 +1 Topo Cyl: -13.74 x 007 Tx: +1.01-5.73 x 007

14. Pre Op Post Op Difference Map

15. TG-PRK Retreatment for PK 43 years old male 18 months post-op PK x 2yrs, PRK x 8 months UVA: 20/100 UVA: 20/40 -1 MR: pl-5.75 x 122 20/40MR: +0.50-1.25 x 180 20/40 Tx: -1.25-5.88 x 130 CT: 485µmCT: 409µm

16. Final Post Op 1 o Tx Pre Op 1 o Tx Post Op 1 o Tx PreOp MR: -1.50-8.00 x 122 20/60 -1 Topo Cyl: 9.40 x 113 Total Tx Cyl: 11.88D Final PostOp MR: UVA: 20/40 -1 MR: +0.50-1.25 x 180 20/40 Difference Map

17. Discussion Post-keratoplasty astigmatism is highly irregular, may be extreme Challenging, often not correctable with contact lenses or glasses TG-PRK aims to regularize the uneven corneal front surface to achieve the desired refractive outcome Any corneal topographic change will lead to an accompanying change in refraction Often not possible to acquire a wavefront map

18. Discussion Removes less tissue Even if VA is not improved, we believe there is an improvement in the quality of vision from smoothening the corneal surface PRK preferred LASIK flap may be difficult along graft-host junction and suture lines Haze is an issue

19. Limitations Quality of vision HOA Contrast sensitivity Vector analysis

20. Conclusions Early results of TG-PRK with TNT shows potential to improve both UVA and BCVA with good efficacy and safety 35% UVA improved to 20/40 or better, none preoperatively More than one third of the patients gained 2 lines or more of BCVA

21. Thank You