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Laser Photoablation
The document discusses laser photoablation, a process that uses high energy UV photons to break molecular bonds, with its discovery credited to Srinivasan and Mayne-Banton in 1982. Key applications include refractive eye surgeries such as LASIK, while also highlighting the potential cytotoxic effects of UV lasers, including DNA damage. The document concludes by reaffirming the importance of photoablation in ophthalmology and the associated risks from UV exposure.
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Laser Photoablation
- 1. LASER PHOTOABLATION University CollegeOf Engineering(UCE),OU DEPARTMENT OF BIOMEDICAL ENGINEERING BY. TADESSE WAKTOLA ZERIHUN KETEMA 25 JAN, 2017 1
- 2. Outlines • Introduction • Processof photoablation • Models • Applications • Effects Conclusion 2
- 3. Introduction Photoablation: Laser interactionmechanism 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
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- 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) = I0 exp(−αz) ii) − ∂I /∂z = α I(z) iii) αI(z) ≥ αIph; αIph threshold value iv) I0 exp(−αz) ≥ Iph v) d = 1/α ln I0 /Iph≈ 2.3 α log10 I0/Iph Ablation depth 6
- 7. Clinical Applications Ophthalmology Refractive RetinalSurgery Correct refractive error eye Myopia(nearsightedness) Hyperopia (farsightedness) Astigmatism LASIK 7
- 8. Effects of Photoablation UVCytotoxicity Sources of UV lasers 8
- 9. Effects of Photoablation UVCytotoxity DNA defects Mutagenesis 248 nm > 193 nm > 308 nm Decreasing order of DNA Effects 9
- 10. Conclusion Photoablation islaser 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. NiemzLaser,Tissue Interactions Fundamentals and Applications,3rd 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
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