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
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2. Outlines
• Introduction
• Process of photoablation
• Models
• Applications
• Effects
 Conclusion
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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)
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4. Photoablation Process
Excitation: AB + hν → (AB)∗,
Dissociation: (AB)∗ → A+B+ Ekin
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5. Principle of Photoablation
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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
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7. Clinical Applications
Ophthalmology
Refractive Retinal Surgery
Correct refractive error eye
Myopia(nearsightedness)
Hyperopia (farsightedness)
Astigmatism
LASIK
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8. Effects of Photoablation
UV Cytotoxicity
 Sources of UV
lasers
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9. Effects of Photoablation
UV Cytotoxity
 DNA defects
Mutagenesis
248 nm > 193 nm > 308 nm
Decreasing order of DNA Effects
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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
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11. References
1.Markolf H. Niemz Laser,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
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12. Thank You
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