Topography-Guided Photorefractive Keratectomy for Irregular Astigmatism After Penetrating Keratoplasty
Narrative Responses:
Purpose
To evaluate the efficacy and safety of a customTopographic Neutralization Technique (TNT) in topography-guided photorefractive keratectomy (TG PRK) for irregular astigmatism following penetrating keratoplasty (PK)
Methods
Retrospective case series. 49 eyes with post keratoplasty astigmatism underwent TG PRK with Allegretto Wavelight (AW) laser using a custom Topography Neutralization Technique (TNT) to modify the manifest refraction based on the refractive changes induced by 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. Rate of re-treatment performed or planned at 12 months recorded
Results
At one year , 23 eyes had sufficient data for analysis, 8(35%) had UCVA of 20/40 or better, none preoperatively. In 11 (48%) BSCVA improved, 8 (35%) gained 2 lines or more, 1 lost 2 lines or more. Range of Pre-operative refractive cylinder 1.75D to 8.00D, and post-operatively ranged 0 to 6.75D. Spherical equivalent improved from -2.32D to -0.87D. Mean astigmatic reduction was 2.89D. Retreatment 17%, delayed epithelialization in 4, corneal haze of greater than 2/4 in 3. 4 eyes greater than 8D cylinder on the AW topolyzer underwent second treatment for residual astigmatism, with improved UCVA in all.
Conclusion
Topography-guided PRK for irregular post-keratoplasty keratoplasty astigmatism has good efficacy and safety. One third were 20/40 or better UCVA compared to none preoperatively, and 43% had BSCVA improved by 1 line or more. Extreme astigmatism post keratoplasty can also be treated with TG PRK, but more often needs second treatment.