Greg T Moloney, David TC Lin,Simon P Holland
To evaluate the efficacy and safety of theVancouver Custom Topographic Neutralization Tech-nique (TNT) in topography-guided photorefractivekeratectomy (TG PRK) for irregular astigmatism inectasia, keratoconus and following penetrating kerato-plasty (PK).
Retrospective chart review of patientsundergoing TG PRK with Allegretto Wavelight (AW)laser using the Vancouver Custom Topography Neu-tralization Technique (TNT) to modify the manifestrefraction based on the refractive changes predictedfrom the plano TG treatment. After treatment, mito-mycin C 0.02% was applied in all cases followed bystandard post-PRK management. Uncorrected visualacuity (UCVA), best spectacle corrected visual acuity(BSCVA), refraction, keratometry (K), topography andhaze on a 1–4 scale are evaluated at 1, 3, 6, 12 and 24months post treatment.
47 post PK, 18 ectasia and 135 keratoconuspatients completed 12 months follow up. In the postPK group, 10 eyes (36%) had UCVA of 20/40 or betterwhile the best UCVA prior to treatment was 20/50. 12(43%) had BSCVA improved, 7 (25%) gained 2 linesor more, while 3 (11%) lost 2 lines or more. In theectasia group, 10/18 (56%) had UCVA of ?20/40. 13(72%) had improved BCVA while 10 (56%) gained 2lines or more. In the keratoconus group 72 (53%) had?20/40 or better uncorrected visual acuity (UCVA), 76(56%) had BCVA improved, 38 (28%) improved BCVA2 lines or more, 5 (4%) lost 2 lines or more. Meanreduction of astigmatism was 1.47 diopters (D). Com-plications included delay in epithelial healing, withsubsequent haze, 2 sufficient to reduce BCVA morethan 2 lines, 1 undergoing PK, HSV keratitis, 1 recov-ering pre-operative BCVA after PTK.
Topography-guided PRK is effective forimproving irregular corneal shape, but is prone toinducing refractive change in the process. TheVancouver custom TNT offers a compensatory ablationprofile for this change, with promising early efficacyand safety in a variety of clinical settings.