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Phacoemulsification
Phacoemulsification
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Phacodynamics basics!

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Basics of phacodynamics

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Phacodynamics basics!

  1. 1. PHACODYNAMICS MODERATOR: DR CHINMAYEE PRESENTER: DR ANJALI H
  2. 2. OUTLINE • History • Introduction • Components- ultrasonic -fluidic • Power of phaco • Needle and hand piece • Aspiration systems • Surge • Venting • Applications
  3. 3. History • February 1965 CHARLES KELMANN: ultrasonic tool to fragment the crytalline lens. • First surgery:3hours,aphakic,rigid IOL.
  4. 4. • 3 developments :technological progress :new surgical technique :foldable IOL
  5. 5. Introduction • Goal of phacoemulsication: • To remove cataract through a small incision to achieve rapid visual rehabilitation.
  6. 6. Three factors Biometry
  7. 7. Surgical skills
  8. 8. • Application of principles of phacodynamics
  9. 9. Basic functions of phaco machine • Ultrasound emulsification • Irrigation • Aspiration
  10. 10. Foot pedal functions • Perfect functioning of this pedal is crucial to the success of the procedure
  11. 11. Foot pedal positions
  12. 12. Phaco comprises of 2 components • Ultrasonic energy • Fluidic circuits
  13. 13. Ultrasonic power • Piezo electric • Magnetosrictive
  14. 14. MAGNETOSTRICTIVE HAND PIECE PIEZOELECTRIC HAND PIECE Electric current induces magnetic field electric energy, translates into oscillations Less efficient power generation More efficient power generation Heats up more readily Heats up slowly Heavy Light weight Less cost More costly Unbreakable Fragile
  15. 15. Power of phaco • Ability to destroy lens nucleus • Depends on: 1. Amplitude 2. Frequency 3.Coupling force
  16. 16. Amplitude Stroke length: penetration of the tip into nuclear mass with each oscillation
  17. 17. Frequency • Determines how much of amplitude will be transformed productively into penetration
  18. 18. Coupling force This can be achieved by: *Pressing against the nucleus *Aspirating *Pressing the nuclear fragment with the second instrument
  19. 19. Phaco needle tip Ultrasonic hand piece Silicon sleeve Silicon hub -Distal opening: aspiration port -Irrigation fluid flows through 2 ports located 180◦
  20. 20. Phaco needle tip • Titanium Tip • Usual Frequency 40 KHz • Usual Amplitude 3/1000 of an inch • Piezoelectric Quartz Crystal • Diameter (19 G-0.9mm,20G-0.6mm) • Bevel angle (0,30,15,30,45)
  21. 21. Phaco needle tip design
  22. 22. Sleeves •Made of silicon material which covers the phaco tip •It protects the cornea and iris from transmitted heat energy by the probe.
  23. 23. Mechanism of action of phaco • Mechanical impact of tip against nucleus • Jackhammer effect • Acoustic waves • Cavitation phenomena
  24. 24. Jack hammer effect
  25. 25. Acoustic shock waves
  26. 26. Cavitations phenomena
  27. 27. Tortional ultrasound •Produces a side-to-side motion of the phaco tip •Reduces the repulsion of nuclear material from the phaco tip.
  28. 28. Phaco hand piece terminologies • Phaco power: ability of hand piece needle tip to cut/emulsify cataract. • Directly related to 1. stroke length 2. frequency 3. efficiency of hand piece
  29. 29. Phaco modes • Constant mode: sculpting the nucleus • Pulsed mode: used in the direct chop of nucleus. • Hyper pulse mode: allows to vary duty cycle. -Soft cataract:low duty cycle 15-20% -Hard cataract:phaco energy is increased with DC 25-33%. -Large cooling time after each phaco:COLD PHACO
  30. 30. Various modes
  31. 31. Duty cycle
  32. 32. Pulse mode
  33. 33. Power can be delivered in various modes:
  34. 34. • Burst mode:This mode provides a surrounding tight seal around the nucleus. -Individual bursts of phaco are ideal for impaling and gripping dense nuclear material for chopping. • Occlusion mode: Ability to change pump speed & power modulation pre and post occlusion
  35. 35. Phaco modes..
  36. 36. Maximum phaco power • Maximum obtainable ultrasonic energy when foot pedal control is fully depressed Actual phaco power • Power actually delivered at a given time proportional to foot pedal position.
  37. 37. Effective phaco time • Total phaco time at 100% phaco power. • Less EPT: Less energy delivered to the eye thus reducing side effects
  38. 38. Fluidics • Balance of fluid inflow and fluid outflow • Irrigation system: inflow : bottle height Outflow : sleeve-incision relationship. Balanced AC dynamics: irrigation=aspiration+leakage from wound • Aspiration system:flow rate:How well particulate matter attracted to phaco tip.
  39. 39. Irrigation system and bottle height A. Bottle height B.Fluidity of the eye C.Evacuation pump D. Exit fluid.
  40. 40. Aspiration systems • Flow rate: quantity of fluid pulled from eye per minute through irrigation tip. • Vaccum : negative suction pressure created by the pump.
  41. 41. Aspiration pumps • Peristaltic pump • Venturi pump • Diaphragmatic pump
  42. 42. Peristaltic pump Rollers Rotation of the pump Compression of the tube in peristaltic manner Milking action of the fluid column
  43. 43. Venturi pump
  44. 44. Diaphragmatic pump
  45. 45. Comparison of pumps Peristaltic Venturi Flow based Vacuum based Vacuum created on occlusion of phaco tip Vacuum created instantly via pump Flow is constant until occlusion Flow varies with vacuum level Drains into a soft bag Drains into a rigid cassette
  46. 46. Rise time • Amount of time required to attain a given level of vacuum • Speed with which the maximum value of vacuum is reached, once the aspiration port is occluded • Rise time ∝ AFR ∝ Pump speed
  47. 47. Rise time v/s pump design
  48. 48. How does it imply?? • Rapid Rise Time : • Less surgical time • Machine responds fast • Infusion should be adequate • Surgeon needs to have quick reflexes. • Margin of safety is less.
  49. 49. Surge • Sudden cessation of occlusion • Occlusion High vacuum Occlusion broken Fluid gushes into Phaco tip Exceeds inflow capacity of irrigation line SHALLOW AC
  50. 50. Surge • means collapse of A.C after occlusion breaks HOW TO PREVENT SURGE?? •Decrease vaccum •Decrease flow rate •Stiff and short tubing •Tighter wounds and raising bottle height •Aspiration bypass system
  51. 51. Aspiration bypass system
  52. 52. Venting •Breaking of vaccum •Air venting •Fluid venting
  53. 53. Venting system • To break the vacuum Air Fluid high time delays for detecting vacuum change low time delays detection for vacuum change Responds slowly to compensate vacuum surge Responds faster to compensate vacuum surge Air venting increases compliance of the system, which increases surge Compliance is less in a system with fluid vents with lesser surge as a result
  54. 54. Central safe zone Area within the CCC margin where phaco can be done safely csz Peripheral unsafe zone
  55. 55. Applications • Phaco-emulsification -Sculpting / Trenching -Segment / Quadrant removal -Epinucleus removal • I /A - Cortex removal
  56. 56. Parameter setting • Stage of surgery • Experience of the surgeon • Machine characteristics
  57. 57. Sculpting • Power- 60 - 70% • AFR -16 - 20 ml/min • Vacuum- 0 - 30 mm Hg
  58. 58. Segment / quadrant removal • Power- 40 - 50% • AFR -24 - 26 ml/min • Vacuum -100 - 400 mm Hg
  59. 59. Epinucleus removal • Power 10 - 30% • AFR 26 - 30 ml/min • Vacuum 200 - 400 mm Hg
  60. 60. Cortex removal • Power- Zero • AFR -24 - 26 ml/min • Vacuum -400 mm Hg
  61. 61. Parameter settings AFR VACCUM POWER BOTTLE HEIGHT Central sculpting 20-25/min 0-15mm Hg 60-70% 25cm Chopping 25-30/min 100- 200mm Hg 50-60% 75cm Quadrant removal 25-30/min 100mm Hg 50% 65cm Epinucleus removal 30-35/min 70-100mm Hg 10% 75cm Cortex aspiration 25-30/min 400mmHg - 65cm
  62. 62. Successful phaco… • Know your machine! • Supervised training • Proper patient selection
  63. 63. References … • MYRON & YANOFF DUKER’S OPHTHALMOLOGY. 3rd edition • Physical and mechanical principles of phacoemulsification and their clinical relevance L.Yow S Basti Alcon Laboratories, Irvine, California, USA .IJO • Phacoemulsification Agarwal .4th edition • Phacodynamics-Barry S Seibel. 4th edition

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