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Topography-guided photorefractive keratectomy for irregular astigmatism following penetrating keratoplasty (PK)

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Session Details

Session Title: Photoablation, Cross-Linking and Intracorneal Ring Segment

Session Date/Time: Monday 07/09/2015 | 08:00-10:30

Paper Time: 09:12

Venue: Room 16

First Author: : S.Holland CANADA

Co Author(s): :    D. Lin   K. Termote                 

Abstract Details


To evaluate the efficacy and safety of the Vancouver Custom Topographic Neutralization Technique (TNT) in topography-guided photorefractive keratectomy (TG PRK) for irregular astigmatism following penetrating keratoplasty (PK)


Pacific Laser Eye Centre, Vancouver, Canada


Retrospective case series. 53 eyes with post keratoplasty astigmatism underwent TG PRK with Allegretto Wavelight (AW) laser using the Vancouver Custom Topography Neutralization Technique (TNT) to modify the manifest refraction based on the refractive changes predicted from the plano TG treatment. After treatment, mitomycin C 0.02% was applied in all cases followed by standard post-PRK management. Uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), refraction and spherical equivalent (SE), keratometry (K), topography and haze on a 1-4 scale are evaluated at 1, 3, 6, 12 and 24 months post treatment


45 eyes met criteria for analysis at 12 months. 14 eyes (31%) had UCVA ≤ 20/40, none preoperatively. 23 (51%) had BSCVA improved. 14 (31%) gained ≥2 lines, 2 (4%) lost ≥2 lines. Pre-operative refractive cylinder ranged from 0.75D to 8.00D, and post-operatively ranged 0.00D to 6.00D. Average SE improved from -3.13±2.18D to -1.38±1.97D. Average astigmatic reduction: 2.93±2.22D. Retreatment rate: 18% (8/45). Delayed epithelialization beyond one week in 4 and corneal haze of greater than 2/4 in 3. 4 eyes with extreme astigmatism greater than 8D on the AW topolyzer require a second treatment for residual astigmatism, with improvement of UCVA in all. Complications include visually significant haze 2 eyes, and delayed epithelization beyond one week 4 eyes


TG PRK for irregular astigmatism after penetrating keratoplasty using the Vancouver custom TNT ablation offers promising early results with good efficacy and safety. Almost 1/3 cases achieved ≥20/40 UCVA compared to none preoperatively, with 51% had BSCVA improved by ≥1 line. Extreme astigmatism post keratoplasty can also be treated with TG PRK, but likely to require a second treatment

Financial Interest:

One of the authors receives consulting fees, retainer, or contract payments from a competing company

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