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

Session Details

Session Title: Surface Ablation II

Session Date/Time: Tuesday 08/10/2013 | 16:30-18:00

Paper Time: 16:42

Venue: Main Lecture Hall (Ground Floor)

First Author: : J.Tan CANADA

Co Author(s): :    S. Holland   D. Lin   G. Moloney        

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).


Laser Eye Centre


Retrospective case series. 47 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, keratometry (K), topography and haze on a 1-4 scale are evaluated at 1, 3, 6, 12 and 24 months post treatment.


Sufficient data was available for analysis on 28 eyes at 1 year. 10 eyes (36%) had UCVA of 20/40 or better while the best UCVA prior to treatment was 20/50. 12 (43%) had BSCVA improved, 7 (25%) gained 2 lines or more, while 3 (11%) lost 2 lines or more. Pre-operative cylinder ranged from -0.75D to -13.50D, and post-operative cylinder ranged from zero to -4.50D. Mean astigmatic reduction was 2.90D. 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 in 2 eyes, and delayed epithelization beyond one week in 4 eyes.


Topography-guided PRK for irregular astigmatism after penetrating keratoplasty using the Vancouver custom TNT ablation offers promising early results with good efficacy and safety. A third of the subjects achieved 20/40 or better UCVA compared to none preoperatively, with 43% had BSCVA improved by 1 line or more. Extreme astigmatism post keratoplasty can also be treated with TG PRK, but likely to require a second treatment.

Financial Interest:


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