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Viscous Flows in the Human Cornea

Viscous Flows in the Human Cornea. By: Molly Fahey Viscous Flows, Fall 2006 December 12, 2006. Background Information/Previous Research. Ultra-short pulsed lasers for biomedical applications Corneal Surgery Dental applications Laser Used for Research (FDA) - Raydiance Desktop Laser

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Viscous Flows in the Human Cornea

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  1. Viscous Flows in the Human Cornea By: Molly Fahey Viscous Flows, Fall 2006 December 12, 2006

  2. Background Information/Previous Research Ultra-short pulsed lasers for biomedical applications • Corneal Surgery • Dental applications Laser Used for Research (FDA) -Raydiance Desktop Laser -Wavelength = 1,550 nm -Pulse Duration ≈ 1 ps

  3. Purpose: Correlation between Viscous Flows and Laser Ablation Research • Biological materials such as a human cornea is made up mostly of water. • Vision is dependent on the hydration of the cornea. • Important to understand how it remains hydrated. • In order to improve on current or develop novel corneal surgery techniques one must fully understand the mechanics of the eye. • What causes the viscous flows in the cornea? • Is gravity a driving force?

  4. What is a Cornea? • The Outermost layer of the eye. • Consists of three layers: • The epithelial membrane (outer most layer) • The stroma (makes up 90% of cornea) • The endothelial membrane Figure 1. Anatomy of Eye Figure 2. Extracted Human Cornea being held by a suction device used in LASIK eye surgery.

  5. Current Corneal Research • Corneal Refractive Surgery • LASIK- Laser-Assisted In SituKeratomileusis • Most popular refractive surgery in America. • 1.3 million American’s had LASIK in 2005. • A flap is made with a mechanical blade. • An excimer laser (ultraviolet light) is used to ablate lenticle in the corneal stroma to correct vision.

  6. Current Corneal Research • Intrastromal Corrective Sugery • Near IR light, which is retinal safe, is focused under the corneal surface in the stroma. • Lenticle is ablated without the creation of a flap.

  7. Current Corneal Research • Corneal Replacement Surgery

  8. Using Fluent /Gambit to determine the nature of the viscous flows within the cornea. • Modeled the Cornea in Gambit as 2 Dimensional Plane wall and Curved Surface. Geometries and Boundary Conditions 0.5 mm 0.5 mm Tamb= 308K Ts=310K 12 mm 12 mm Tamb= 308K Ts=310K

  9. Cornea as a Flat Plane Wall • Gravity is driving the free convective flows in the cornea. • Without gravity as an operating condition in Fluent there was no velocity. Velocity Vectors: Top Half of the cornea

  10. Velocity Vectors in the Center Region of the Cornea.

  11. Velocity Vectors: Curved Geometry

  12. Velocity vector: Center region of curved Geometry

  13. Velocity Vector: Top Region of Curved Geometry

  14. Pressure Contours Flat Geometry Curved Geometry

  15. Temperature Contours Flat Geometry Curved Geometry

  16. Conclusion: • Free convective flows within the cornea. • Buoyancy is the driving force for these flows • Without gravity there was no velocity • The flows in the cornea maintain hydration of the cornea which is necessary for vision.

  17. References: Kumar S, Acharya S, Beuerman R, Palkama A. 2005. Numerical Solution of Ocular Fluid Dynamics in a Rabbit Eye: Parametric Effects. Annals of Biomedical Engineering. 3493): 530-544 Li LY, Tighe BJ, Ruberti JW. 2004. Mathematical Modelling of Corneal Swelling. Biomechanical Model Mechanobiology. 3: 114-123 Ridouane EH, Campo A. 2005. Model for the Heat Transmission in the Human Eye. Proceedings of the 2005 International Mechanical Engineering Congress and Exposition; 2005 November 5-11; Orlando, Florida, USA: ASME. p 535-539.

  18. Questions?

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