Basics of phacodynamics

1. PHACODYNAMICS
MODERATOR: DR CHINMAYEE
PRESENTER: DR ANJALI H

2. OUTLINE
• History
• Introduction
• Components- ultrasonic
-fluidic
• Power of phaco
• Needle and hand piece
• Aspiration systems
• Surge
• Venting
• Applications

3. History
• February 1965 CHARLES KELMANN: ultrasonic
tool to fragment the crytalline lens.
• First surgery:3hours,aphakic,rigid IOL.

4. • 3 developments :technological progress
:new surgical technique
:foldable IOL

5. Introduction
• Goal of phacoemulsication:
• To remove cataract through a small incision to
achieve rapid visual rehabilitation.

6. Three factors
Biometry

7. Surgical skills

8. • Application of principles of phacodynamics

10. Basic functions of phaco machine
• Ultrasound emulsification
• Irrigation
• Aspiration

11. Foot pedal functions
• Perfect functioning of this pedal is crucial to
the success of the procedure

12. Foot pedal positions

13. Phaco comprises of 2 components
• Ultrasonic energy
• Fluidic circuits

14. Ultrasonic power
• Piezo electric
• Magnetosrictive

16. 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

17. Power of phaco
• Ability to destroy lens nucleus
• Depends on: 1. Amplitude
2. Frequency
3.Coupling force

18. Amplitude
Stroke length: penetration of the tip into nuclear
mass with each oscillation

19. Frequency
• Determines how much of amplitude will be
transformed productively into penetration

20. Coupling force
This can be achieved by:
*Pressing against the nucleus
*Aspirating
*Pressing the nuclear fragment
with the second instrument

21. Phaco needle tip
Ultrasonic hand piece
Silicon sleeve
Silicon hub
-Distal opening:
aspiration port
-Irrigation fluid flows
through 2 ports located
180◦

23. 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)

24. Phaco needle tip design

26. Sleeves
•Made of silicon material which
covers the phaco tip
•It protects the cornea and iris
from transmitted heat energy by
the probe.

27. Mechanism of action of phaco
• Mechanical impact of tip against nucleus
• Jackhammer effect
• Acoustic waves
• Cavitation phenomena

28. Jack hammer effect

29. Acoustic shock
waves

30. Cavitations phenomena

31. Tortional ultrasound
•Produces a side-to-side motion of the
phaco tip
•Reduces the repulsion of nuclear
material from the phaco tip.

32. 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

33. 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

34. Various modes

35. Duty cycle

36. Pulse mode

37. Power can be delivered in various
modes:

39. • 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

40. Phaco modes..

41. 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.

42. Effective phaco time
• Total phaco time at 100% phaco power.
• Less EPT: Less energy delivered to the eye thus
reducing side effects

43. 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.

44. Irrigation system and bottle height
A. Bottle height
B.Fluidity of the eye
C.Evacuation pump
D. Exit fluid.

45. Aspiration systems
• Flow rate: quantity of fluid pulled from eye
per minute through irrigation tip.
• Vaccum : negative suction pressure created by
the pump.

46. Aspiration pumps
• Peristaltic pump
• Venturi pump
• Diaphragmatic pump

47. Peristaltic pump
Rollers
Rotation of the pump
Compression of the tube
in peristaltic manner
Milking action of the fluid
column

48. Venturi pump

49. Diaphragmatic pump

50. 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

51. 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

52. Rise time v/s pump design

53. 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.

54. Surge
• Sudden cessation of occlusion
• Occlusion High vacuum Occlusion
broken Fluid gushes into Phaco tip
Exceeds inflow capacity of irrigation line
SHALLOW AC

55. 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

56. Aspiration bypass system

57. Venting
•Breaking of
vaccum
•Air venting
•Fluid venting

58. 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

60. Central safe zone
Area within the CCC margin where phaco can be done safely
csz
Peripheral unsafe zone

61. Applications
• Phaco-emulsification
-Sculpting / Trenching
-Segment / Quadrant removal
-Epinucleus removal
• I /A - Cortex removal

62. Parameter setting
• Stage of surgery
• Experience of the surgeon
• Machine characteristics

63. Sculpting
• Power- 60 - 70%
• AFR -16 - 20 ml/min
• Vacuum- 0 - 30 mm Hg

65. Segment / quadrant removal
• Power- 40 - 50%
• AFR -24 - 26 ml/min
• Vacuum -100 - 400 mm Hg

67. Epinucleus removal
• Power 10 - 30%
• AFR 26 - 30 ml/min
• Vacuum 200 - 400 mm Hg

68. Cortex removal
• Power- Zero
• AFR -24 - 26 ml/min
• Vacuum -400 mm Hg

69. 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

70. Successful phaco…
• Know your machine!
• Supervised training
• Proper patient selection

71. 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