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

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

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)

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

Procedure Trans-epithelial PTK, followed by TG PRK with T-CAT software and TNT Mitomycin-C 0.02% for 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

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

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

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

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

TG-PRK for PK Pre-op13 Months Post-op UVA: 20/300UVA: 20/50 -2 MR: x /80 -1 MR: pl-4.00 x /40 +1 Topo Cyl: x 007 Tx: x 007

Pre Op Post Op Difference Map

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 /40MR: x /40 Tx: x 130 CT: 485µmCT: 409µm

Final Post Op 1 o Tx Pre Op 1 o Tx Post Op 1 o Tx PreOp MR: x /60 -1 Topo Cyl: 9.40 x 113 Total Tx Cyl: 11.88D Final PostOp MR: UVA: 20/40 -1 MR: x /40 Difference Map

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

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

Limitations Quality of vision HOA Contrast sensitivity Vector analysis

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

Thank You