Phaco 2 / Chop Settings - Compact Phaco Machine

What Is "Phaco 2 / Chop" Mode?

Typical Phaco 2 / Chop Parameter Values

Why These Settings Make Sense - Parameter by Parameter

1. Burst Mode (instead of Continuous)

• In burst mode, ultrasound is delivered in short rapid pulses triggered by foot pedal pressure, with off-periods between each burst
• The off-periods allow heat dissipation - reducing the risk of wound burn
• Bursts maintain tight occlusion grip on the nuclear fragment during the "hold" phase of chopping
• Dr. David Chang notes: "High vacuum + burst mode optimizes the solid purchase needed to chop dense nuclei into fragments"
• Compare to sculpting (Phaco 1) where continuous US is used because no occlusion occurs

2. High Vacuum (475 mmHg)

• Vacuum = holding/gripping power at the phaco tip
• During chopping, you need to impale and hold the nucleus firmly while the chopper comes in - this requires high vacuum
• Once occlusion is achieved at the tip, high vacuum locks the fragment in place
• At 475 mmHg, you get reliable nuclear purchase even for harder nuclei (LOCS III grade 3-4)
• Safety note: High vacuum creates risk of post-occlusion surge when the fragment suddenly emulsifies through the tip. Dr. Chang recommends doing a "surge test" to find your machine's maximum safe vacuum before routine use

3. High Flow Rate (40 mL/min - double the sculpt setting)

• Flow rate governs speed and distal followability (how efficiently fragments are drawn to the tip)
• Higher flow in Phaco 2 serves two purposes:
  • Faster nuclear fragment removal once chopped
  • Anterior chamber stability - higher inflow maintains chamber depth during high-vacuum maneuvers
• The jump from 18 mL/min (sculpt) to 40 mL/min (chop) reflects the transition from a non-occlusive to an occlusion-based technique

4. Power at 70% (slightly above sculpt)

• During chopping, less pure US energy is needed compared to sculpting (chopping mechanically fractures the nucleus)
• But power is increased to 70% (vs 60% sculpt) because the fragments being emulsified are often harder, denser material from the endonucleus
• Burst delivery at 70% means actual duty cycle is lower than 70% continuous - effectively reducing total energy delivered to the eye (CDE = Cumulative Dissipated Energy)

Why the Phaco 2/Chop Program Is Distinct from Phaco 3/Quad

Key Safety Principles for the Chop Setting

1. Surge management: The primary risk at 475 mmHg vacuum is post-occlusion surge when a fragment suddenly passes through the tip. Use anti-surge algorithms if your machine offers them.
2. The "surge test" (Dr. Chang): Hold a small nuclear fragment at foot position 2, wait for the vacuum-max beep, then release and observe. If surge is excessive, reduce vacuum by 10% increments until safe.
3. Transition timing: Switch from Phaco 1 → Phaco 2 only after your groove is complete and the first chop is made. Don't use Chop settings during sculpting (the high flow + vacuum with no occlusion wastes energy and destabilizes the chamber).
4. Adjust for nucleus density: For softer nuclei (LOCS I-II), you may reduce the Phaco 2 vacuum to 300-350 mmHg to avoid inadvertent capsule stress. The published 475 mmHg is optimized for moderate-to-dense nuclei.
5. For compact machines specifically: Since compact phaco machines (CataRhex 3, Stellaris Elite) may use peristaltic pumps, remember that vacuum builds during occlusion - you're setting the maximum vacuum, not a fixed vacuum. Flow rate is the primary active variable until occlusion occurs.

Note on the Image

Your Phaco 2 / Chop Settings - Detailed Analysis

Your Settings Summarized

Understanding Each Setting

1. Threshold Vacuum: 150 mmHg

• Softer to moderate nuclei (LOCS I-III)
• Beginners / safety-conscious surgeons
• Compact machines with smaller fluidic tubing (less surge buffer)

2. Power: 35% Linear

• Cumulative Dissipated Energy (CDE)
• Risk of wound burn
• Repulsion of nuclear fragments away from tip
• Endothelial cell trauma from cavitation

3. Long Pulse Mode with 60% Duty Cycle

• Micropulse = very short pulses (4-10 ms on-time)
• Continuous = no off-time at all (100% duty cycle)

• Total cycle = 500 ms
• US ON for 300 ms
• US OFF for 200 ms

• Aspiration can draw nuclear fragments to the tip during the quiet phase (followability)
• Heat dissipation occurs between pulses
• Nuclear material doesn't "chatter" away from the tip as with continuous mode

4. Occlusion Mode Power Delivery

• US only cuts when there is actually nuclear material at the tip - you cannot inadvertently hit capsule, iris, or corneal endothelium with ultrasound if the tip is free
• Eliminates "free-phaco" - energy wasted cutting fluid/BSS instead of nucleus
• Reduces total CDE significantly
• Reduces wound heating - in non-occlusion mode, continuous US in an unoccluded tip heats the incision even with no nucleus present
• Matches the "vacuum first, then phaco" philosophy of modern chop techniques: build grip → confirm occlusion → only then emulsify

The Three-Way Comparison: Your Settings vs Non-Occlusion vs Non-Threshold

Practical Implications for Your Surgical Steps

1. Foot position 1 - Irrigation only. AC maintained.
2. Foot position 2 - Aspiration begins. Vacuum builds. Tip approaches nucleus. At this stage, NO US fires even if you enter position 3, because vacuum has not yet reached 150 mmHg.
3. Tip contacts nucleus, occlusion begins - Vacuum rises. As it crosses 150 mmHg threshold, the machine recognizes occlusion.
4. Foot position 3 - US now activates at linear 35% (proportional to pedal depth), in long pulses at 60% duty cycle. The phaco tip impales the nucleus and locks it via vacuum.
5. Chopper comes in - You chop while vacuum holds the nucleus. Minimal US is needed here - the chopper does the mechanical work.
6. Fragment emulsifies/aspirates - As the fragment passes through the tip, vacuum suddenly drops below 150 mmHg → US automatically stops → no free-phaco in the AC.
7. Repeat for each fragment.

Bottom Line

• Occlusion mode eliminates free phaco and protects capsule/endothelium
• 150 mmHg threshold is a moderate trigger that confirms tip grip without excessive surge risk
• 35% linear long pulse at 60% duty cycle delivers enough cutting power to emulsify gripped fragments while the 40% off-time allows followability and heat dissipation
• Total CDE is substantially lower than continuous non-occlusion mode at the same nominal 35% power

Phaco 2 / Chop Settings - Simply Explained

Think of the Phaco Tip Like a Vacuum Cleaner with a Drill

• The vacuum = suction that grabs and holds the lens piece
• The ultrasound (US) power = the drill/vibration that breaks it up
• The foot pedal = your control switch for both

Your 4 Settings, Simply

1. Threshold Vacuum 150 mmHg = "Confirm you've caught something before cutting"

• Below 150 mmHg = tip is floating free in the eye = US stays off
• At/above 150 mmHg = tip has gripped the nucleus = US is now allowed to fire

2. Occlusion Mode = "Only cut when you're holding something"

3. 35% Power, Linear = "Gentle power, you control how much"

4. Long Pulse, 60% Duty Cycle = "Bursts of cutting with breathing gaps"

• Cool down the incision
• Allow suction to pull fragments toward the tip during the quiet moments
• Reduce the "bouncing away" of lens pieces

|--- ON (60%) ---|-- OFF (40%) --|--- ON (60%) ---|-- OFF (40%) --| ...

The Big Picture - Why These Settings Work Together

1. You bring the tip near the lens and press pedal to position 2 - suction starts
2. The tip touches the lens and starts to grip it - vacuum rises
3. At 150 mmHg - machine says "you've got a grip" - US is now armed
4. You press pedal to position 3 - US fires in long pulses (60% on/40% off) at up to 35% power
5. The tip vibrates and breaks up the piece it's holding
6. The piece gets sucked away - vacuum drops below 150 mmHg - US automatically stops
7. Tip is free again - no US firing - safe to reposition
8. Repeat for next piece

Non-Occlusion + Non-Threshold Mode in Comparison - Simply Put

Setting 1 vs Setting 2 - Simple Comparison

First, the Key Revelation: Both Are WhiteStar Settings

• 6/6 (50%) = WhiteStar micropulse: 6ms ON / 6ms OFF = 50% duty cycle
• 6/4 (60%) = WhiteStar micropulse: 6ms ON / 4ms OFF = 60% duty cycle

The Simple Analogy: A Strobe Light

• Every time the light flashes = US ON (cutting)
• Every time the light is off = US OFF (rest, suction works, heat escapes)

Side-by-Side Comparison

What This Means Practically

Setting 1 - 6/6 (50%) - "Equal Work and Rest"

ON--OFF--ON--OFF--ON--OFF--ON--OFF
6ms  6ms  6ms  6ms  6ms  6ms ...

• For every 6ms of cutting, there is an equal 6ms of rest
• The tip is cutting half the time
• More followability - the longer relative off-time lets suction draw fragments to the tip during quiet periods
• Less heat - more time for the incision to cool
• Better for softer nuclei or epinucleus removal where you want fragments to flow freely to the tip
• Lower total energy delivered per second

Setting 2 - 6/4 (60%) - "More Work, Less Rest"

ON----OFF--ON----OFF--ON----OFF
6ms   4ms  6ms   4ms  6ms   4ms ...

• For every 6ms of cutting, there is only 4ms of rest
• The tip is cutting 60% of the time
• More cutting efficiency - fires more frequently, emulsifies harder material faster
• Slightly more heat than Setting 1, but still far cooler than continuous mode
• Better for denser, harder nuclear fragments where you need more actual cutting power
• Higher total energy delivered per second

Energy Delivered - Simple Math

When Would You Use Each?

One-Line Summary

Setting 1 (6/6, 50%) = gentler, cooler, better followability - good for softer lenses and epinucleus. Setting 2 (6/4, 60%) = slightly more aggressive cutting - good for denser nuclear fragments.

The White Star vs Yellow Star - Two Phases of One Smart Program

The Core Concept First

WHITE STAR icon = tip is FREE (not blocked)
YELLOW STAR icon = tip is OCCLUDED (blocked by nucleus)

• Vacuum below 150 mmHg → machine uses the White Star (Setting 1) parameters
• Vacuum rises to/above 150 mmHg → machine automatically switches to Yellow Star (Setting 2) parameters

Your Two Settings Decoded

Why Different Settings for Each Phase?

When the tip is FREE (White Star, 6/6, 50%)

• There is no nuclear material to cut - you don't need aggressive power
• The priority is followability - drawing fragments toward the tip
• The equal 6ms/6ms on-off gives maximum suction time during the off-phase to pull fragments in
• 50% duty cycle = less energy = less heat = less repulsion of fragments
• Continuous delivery at low duty cycle means smooth, non-aggressive tip behaviour

When the tip is OCCLUDED (Yellow Star, 6/4, 60%)

• There IS nuclear material at the tip that needs to be actively emulsified
• You need slightly more cutting power to break through the gripped piece
• The shorter off-gap (4ms vs 6ms) means more pulses per second and more total energy
• 60% duty cycle = more US on-time = more efficient emulsification of the occluded fragment
• Still pulse mode (not continuous) so heat and surge are controlled

The Automatic Switching - Step by Step

Step 1: Pedal pos 2 → Aspiration starts, vacuum builds
         → Vacuum < 150 mmHg
         → WHITE STAR active (6/6, 50%)

Step 2: Pedal pos 3 → US fires gently at 50% duty cycle
         → Tip approaches nucleus, still not fully blocked
         → Gentle energy, good followability

Step 3: Nucleus occludes the tip
         → Vacuum climbs to 150 mmHg (threshold)
         → Machine AUTOMATICALLY SWITCHES to YELLOW STAR (6/4, 60%)

Step 4: US now fires at 60% duty cycle
         → More cutting power, fragment being emulsified
         → Fragment passes through tip

Step 5: Occlusion breaks → vacuum drops below 150 mmHg
         → Machine AUTOMATICALLY SWITCHES BACK to WHITE STAR
         → Gentle mode resumes while tip repositions

Step 6: Repeat for next fragment

Why This Dual-Phase Design Matters - The Importance

1. Safety: No Wasted Energy

2. Lower Total CDE (Cumulative Dissipated Energy)

3. Prevents Wound Burn

4. Better Efficiency When It Counts

5. Surge Prevention

Simple One-Line Summary

White Star (6/6, 50%) = gentle mode when tip is free - protect the eye, attract fragments Yellow Star (6/4, 60%) = efficient cutting mode when tip is gripping nucleus - emulsify faster The machine switches between them automatically every time the vacuum crosses 150 mmHg - you don't have to do anything. This is the intelligence built into WhiteStar occlusion mode.

• Vacuum (the mmHg number shown)
• Power % (the two numbers - unoccluded and occluded)
• The on/off ratio (e.g. 6/4, 8/4, etc.)
• Mode (pulse, long pulse, continuous)
• Flow rate (mL/min)

Phaco 3 / Quad Settings - What to Expect and Why

How Phaco 3 Differs from Phaco 2 in Purpose

Expected Phaco 3 Settings on WhiteStar Signature

Vacuum - Higher than Phaco 2

• Loose fragments are smaller and harder to grip - they bounce away from the tip
• You need high vacuum to lock the fragment quickly before it migrates posteriorly
• Higher vacuum = faster occlusion = shorter time to emulsification = less total US energy

Power - Lower than Phaco 2

• Chopped fragments are already smaller - they need less US to emulsify
• High vacuum does most of the work - fragments are sucked through the tip with minimal US
• Less power = less repulsion = fragments stay at the tip
• Capsule is now exposed - any excess energy is more dangerous

Mode - Pulse with Lower Duty Cycle

Phaco 2 (Chop):    ON---OFF- ON---OFF-  (60% on, shorter rest)
Phaco 3 (Quad):    ON----OFF---- ON----OFF----  (33-43% on, longer rest)

The White Star / Yellow Star Dual Phase in Phaco 3

White Star (Free tip) - Lower duty cycle

• Even lower duty cycle (e.g. 33-43%)
• Smooth, gentle aspiration draws loose fragments toward the tip
• No wasted energy, no repulsion

Yellow Star (Occluded tip) - Slightly higher duty cycle

• Slightly higher duty cycle kicks in
• Efficiently emulsifies the gripped piece
• Then immediately drops back to gentle mode

The Key Difference Between Phaco 2 and Phaco 3 in Simple Terms

The Simple Analogy

• Phaco 2 (Chop) = You're trying to stab a steak and cut it - you need a firm grip and good cutting power
• Phaco 3 (Quad) = You're trying to vacuum up loose crumbs - you need gentle suction and minimal disturbance, or the crumbs scatter

Phaco 3 / EPI Program - Sovereign Compact - Full Explanation

What I Can See on Screen

Now Your Question: Why Does the White Star NOT Change to Yellow?

What you're seeing in the Occluded power panel:

OCCLUDED
   20
LINEAR
VARIABLE WS ★

The Answer: "Variable WS" is Different from Fixed WhiteStar

Fixed WhiteStar (shown with solid White or Yellow star icon)

• Uses a fixed, preset on/off ratio (e.g. 6/4 = 60%)
• The duty cycle is constant - it does not change with pedal position
• This is what your Phaco 2 used (6/6 for unoccluded, 6/4 for occluded)
• Icon = solid coloured star (white when unoccluded, yellow when occluded)

Variable WhiteStar (shown with faded/outline star ★)

• The duty cycle changes dynamically as you depress the pedal further into position 3
• Light pedal press = lower duty cycle (more off-time, gentler)
• Deep pedal press = higher duty cycle (more on-time, more cutting)
• The machine cannot pre-assign a single fixed on/off ratio to display
• Therefore it shows a faded/outline star to indicate "variable - no fixed ratio assigned"
• There is no yellow star because the ratio changes continuously - it cannot be pre-coloured

Why Variable WS for the EPI Occluded Phase?

• The epinuclear shell is thin, soft, and variable in thickness
• Sometimes you grip a thick area, sometimes a thin area
• You need dynamic power control - not a fixed preset
• Variable WS lets you feather the pedal to give exactly the right amount of energy for what's at the tip at that moment
• Too much power = capsule rupture risk
• Too little power = clogging, incomplete removal

Full Parameter Breakdown - EPI Program

ASP Rate (Flow)

• Unoccluded: 28 cc/min - draws epinuclear material toward tip
• Occluded: 24 cc/min - reduces flow when occluded to prevent surge

Vacuum

• Max Vac: 180 mmHg Linear - much lower than Phaco 2's max
• Threshold: 90 mmHg - very low trigger, because epinucleus is soft and occludes the tip easily even at low vacuum
• Linear vacuum = vacuum builds proportionally with pedal depth, giving fine control

Power

• Unoccluded: 15% - Continuous - WhiteStar 6/4 (60%)
  • Very low 15% power when tip is free
  • Gentle continuous energy just to keep tip clear and attract soft material
  • 60% duty cycle with fixed 6/4 ratio
• Occluded: 20% - Linear - Variable WS
  • Slightly higher 20% max when occluded - more cutting needed once gripped
  • But linear + variable WS = you control both power AND duty cycle simultaneously via pedal depth
  • Maximum adaptability for soft, delicate epinuclear material

Comparison: Phaco 2 (Chop) vs EPI (Phaco 3)

Summary in Simple Terms

Why no yellow star? Because the occluded power in EPI uses Variable WhiteStar - the duty cycle changes dynamically as you press the pedal, so there is no fixed on/off ratio to display. The faded star tells you "WhiteStar is active, but it's variable - you control it with your foot."

Why such low settings overall? EPI mode is handling the softest material in the eye, closest to the posterior capsule. Everything is dialled down - low vacuum, low threshold, low power - to maximise safety at the most dangerous moment of the procedure.