1. 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

2. 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

3. 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

4. Pre-op: UVA: 20/100 BCVA: 20/60, +1.75-1.25X75 9 months post-op: UVA: 20/50 BCVA: 20/25 -, +2.50sph

5. Pre-op: UVA: 20/150 BCVA: 20/30 +2, -1.75-0.75X75 4 months post-op: UVA:20/20 BCVA: 20/20, -0.50-0.50X125

6. Pre-op: UVA: 20/300 BCVA: 20/30 -, -3.50-5.50X65 4 months post-op: UVA:20/60 BCVA: 20/40, -0.50-3.50X20

7. Pre-op: UVA: 20/300 BCVA: 20/40 -, -4.25-4.00X75 4 months post-op: UVA:20/50 BCVA: 20/30, -0.75-1.00X135

8. Pre-op: UVA:CF BCVA: 20/30, -5.50-4.75x55 2.5 months post-op: UVA:20/40 BCVA: 20/30 +, -0.25-0.50X95

9. Pre-op: UVA: BCVA: 20/40 -, -6.00-5.00X135 2.5 months post-op: UVA:20/200 BCVA: 20/30, -2.50-1.00X50

10. 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

11. 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