Topographically-guided Photorefractive Keratectomy(TG- PRK) for keratoconus (KC) with neutralization (TNT) and simultaneous collagen cross-linking Simon Holland David T.C Lin WCCVI April 2010 *authors have no financial interests
Purpose To evaluate the efficacy, predictability, and safety of topographically-directed photorefractive keratectomy (TG-PRK) in contact lens intolerant keratoconus using the Wavelight Allegretto laser with and without collagen cross-linking
Methods A topographical neutralization technique (TNT) was used to estimate the refractive change on a plano topographical treatment using the Wavelight Allegretto laser Treatment was modified based on the manifest refraction 36 eyes of 22 patients underwent trans-epithelial TG-PRK Best corrected vision (BSCVA) and eccentricity were evaluated at three, six, and twelve months (Group 1) Additional 27 eyes received simultaneous CXL (Group 2) with an adjusted nomogram
Pre-op: UVA: 20/100 BCVA: 20/60, X75 9 months post-op: UVA: 20/50 BCVA: 20/25 -, +2.50sph
Pre-op: UVA: 20/150 BCVA: 20/30 +2, X75 4 months post-op: UVA:20/20 BCVA: 20/20, X125
Pre-op: UVA: 20/300 BCVA: 20/30 -, X65 4 months post-op: UVA:20/60 BCVA: 20/40, X20
Pre-op: UVA: 20/300 BCVA: 20/40 -, X75 4 months post-op: UVA:20/50 BCVA: 20/30, X135
Pre-op: UVA:CF BCVA: 20/30, x months post-op: UVA:20/40 BCVA: 20/30 +, X95
Pre-op: UVA: BCVA: 20/40 -, X months post-op: UVA:20/200 BCVA: 20/30, X50
Results Improved uncorrected vision (UCVA) was achieved in 32 out of 36 eyes at 12 months with improved best corrected vision (BSCVA) in 19/36 16 unchanged and two eyes lost two lines (Group 1) In the cross-linking group (2), 23/27 eyes had improved UCVA and one lost >2 lines requiring corneal transplant
Conclusions: Contact lens intolerant keratoconus patients considering corneal transplants or ring segments may have an alternative with Topo-directed PRK Topographic cylinder – poor correlation with refractive cylinder (ORA) Topographic neutralizing technique (TNT) to refine refractive algorithms Outcomes better with forme fruste and mild keratoconus – Investigational Topographical neutralization is an effective method for improving results in Topo-directed PRK in KC patients Simultaneous collagen cross-linking may add to long term stability, but early results are inconclusive