1. Influence of Keratoplasty Technique on Corneal Biomechanical Properties in Keratoconus Hans R Vellara, Noor Q Ali, Charles NJ McGhee, Dipika V Patel Department of Ophthalmology University of Auckland, New Zealand nz national eye centre The authors have no financial interests to disclose

2. Biomechanics Elastic Viscous The cornea is viscoelastic

3. Biomechanics & Keratoconus Keratoconus – underlying biomechanical failure Penetrating Keratoplasty (PKP) Deep Anterior Lamellar Keratoplasty (DALK) End stage management options

4. Aims To determine if corneal biomechanics are closer to normal after corneal transplantation To determine the effect of corneal transplantation type on corneal biomechanical properties

5. Methods Prospective cross sectional study 33 PKP and 23 DALK eyes Exclusion: <3/12 post-surgery corneal oedema current rejection raised IOP Examinations: Slit-lamp Pentacam tomography AS – OCT CorVis ST

6. What is it? Air Tonometer Ultra high speed Scheimpflug camera How does it work? Air puff indents cornea Video 4333 frames/sec Calculates a range of output measurements Parameters describe in vivo biomechanics

7. CorVis ST - Parameters Applanation1 Time Length Velocity Highest Concavity Deformation Amplitude (DA) Radius of Curvature (RoC) Peak Distance (PD) Applanation2 Time Length Velocity Comparison of above parameters between PKP and DALK

8. Results MeanPKPDALKp-value Age (years): 35.637.50.61 Time from surgery (months):83.291.10.42 Corneal thickness (µm):534594<0.001 Peak distance (PD)4.83.40.03 All other CorVis ST parameters: p-value (>0.05) CorVis ST – PKP vs. DALK Two corneas overlapped at highest concavity (similar CCT and IOPs).

9. Results – See attached video PKP vs. DALK vs. Normal PKP vs. DALK vs. KC DA1.161.181.38 RoC7.206.314.79 3 corneas overlapped at highest concavity. The deformation profiles are very similar. p-value: <0.05 3 corneas overlapped at highest concavity. The deformation profile of the keratoconic cornea (green) differs from the others.

10. Conclusion Corneal biomechanical properties after PKP and DALK are similar However, the difference in PD may indicate a more viscous cornea after DALK Biomechanical properties after corneal transplant for keratoconus resemble normal corneas