Laser Photoablation

This presentation clearly explains laser photoablation process, its models, applications, and effects.

1. LASER PHOTOABLATION University College Of Engineering(UCE),OU DEPARTMENT OF BIOMEDICAL ENGINEERING BY. TADESSE WAKTOLA ZERIHUN KETEMA 25 JAN, 2017 1

2. Outlines Introduction Process of photoablation Models Applications Effects Conclusion 2

3. Introduction Photoablation : Laser interaction mechanism by which molecular bonds are broken using high energy UV photons Discovery: First by Srinivasan and Mayne-Banton (1982) First studies: PMMA modeled by Garrison and Srinivasan (1985) 3

4. Photoablation Process Excitation: AB + hν → (AB) ∗ , Dissociation: (AB) ∗ → A+B+ Ekin 4

5. Principle of Photoablation 5

6. Models of Photoablation Dependence of ablated depth on incident laser intensity Modeled: By Researchers Srinivasan and Mayne-Banton (1982) Andrew et al. (1983) Deutsch and Geis (1983) Garrison and Srinivasan (1985) Fundamental : Lambert Law of light absorption i ) I(z) = I exp(− αz ) ii) − ∂I /∂z = α I(z) iii) αI (z) ≥ αIph ; αIph threshold value iv) I exp(− αz ) ≥ Iph v) d = 1/α ln I / Iph ≈ 2.3 α log10 I / Iph Ablation depth 6

7. Clinical Applications Ophthalmology Refractive Retinal Surgery Correct refractive error eye Myopia(nearsightedness) Hyperopia (farsightedness) Astigmatism LASIK 7

8. Effects of Photoablation UV Cytotoxicity Sources of UV lasers 8

9. Effects of Photoablation UV Cytotoxity DNA defects Mutagenesis 248 nm > 193 nm > 308 nm Decreasing order of DNA Effects 9

10. Conclusion Photoablation is laser interaction that breaks molecular bonds using UV Photoablation is used in refractive eye surgery UV photons used in photoablation are associated with effects of mutagenesis and cytotoxicty 10

11. References 1.Markolf H. Niemz Laser,Tissue Interactions Fundamentals and Applications,3 rd edition 2.E E Manche,J Carr ,WW Haw, and P S Hersh Excimer Laser refractive surgery 3. http://www.phakosopht.com/Lasik 4. Ophthalmology : Expert Consult: Online and Print by Myron Yanoff and Jay S. Duker,2013 11

12. Thank You 12