Corneal cross linking for the treatment of keratectasia after lasik and for treatment of progressive keratoconus

1. UV-A / Riboflavin corneal cross linking Prof. Michael Mrochen, PhD Institute of Refractive and Ophthalmic Surgery, Zürich, Switzerland Swiss Federal Institute of Technology

2. Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion ... cross linking is used for dental fillings ...

3. Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion Cross-Linking for stiffening ocular tissue structures Figure in courtesy of Dr. Spoerl

4. Photoreaction pathway Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion

5. Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion Cornea with Ribo + UV Cornea without UV but with Ribo R. Doyle Stulting, MD, PhD Ijeoma M. Asota, MD Barbara S. Fant, PharmD Henry F. Edelhauser, PhD

6. Riboflavin concentration in the stroma Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion R. Doyle Stulting, MD, PhD Ijeoma M. Asota, MD Barbara S. Fant, PharmD Henry F. Edelhauser, PhD

7. Stress – strain measurements Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion - A standardised sample of the material is placed in a machine that applies an axial force - An extensometer is used to measure the extension corneal strip

8. Stress – strain measurements: human cornea Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion - 5 untreated - 5 cross-linked with clinical parameters E. Spörl strain in % stress in 10 5 Pa cross- linked untreated increase factor = 4.5 E = 1.3 MPa E = 5.9 MPa

9. Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion Anterior Flap Posterior Flap 3 mW/cm 2 0 mu 200 mu 400 mu 100% 25% 6% Percentage of original irradiance E. Spörl

10. Corneal cross linking Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion Endothelium riboflavin 3 mW/cm 2 / 30 min

11. Corneal cross linking for keratoconus Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion Preoperative corneal topography

12. Corneal cross linking for keratoconus Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion Postoperative corneal topography 5 years after treatment

13. Corneal cross linking for iatrogenic keratectasia Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion untreated treated

16. Introduction UV-A / Riboflavin tissue interaction Diffusion Biomechanical effect Safety aspects Clinical outcomes Future perspectives Conclusion The combination of Riboflavin and UV light have been shown to increase the stiffness of ocular tissue structures. Corneal cross linking is an easy conservative treatment to stop the progression of keratectasia. Corneal cross linking procedure are already performed international (more 1000 a month). FDA clinical trails for corneal cross linking have been started in January 2008.

17. Thank you very much for your attention!