Phaco Machine Settings for Beginners: Peristaltic vs Venturi, Vacuum, Flow, Power and Fixing Surge
Last updated: November 2026
The phaco machine balances fluid coming in (inflow) with fluid and lens material going out (outflow) while ultrasound breaks up the nucleus. Understanding a few settings (vacuum, aspiration flow, inflow pressure and power) lets you set up any machine safely, recognise surge, and adjust when things are not working. Every machine is different, so use these as principles and your unit's presets as the starting point.
Inflow and outflow
- Inflow comes from the bottle by gravity (bottle height, in cm) or from active pressurised systems that set the intraocular pressure in mmHg (e.g. Alcon Centurion active fluidics). Higher inflow keeps the chamber deeper and more stable.
- Outflow is through the aspiration line (controlled by the pump) and through wound leak.
- The chamber is stable when inflow is greater than or equal to outflow. When a block clears suddenly and outflow jumps, the chamber collapses: this is surge.
Peristaltic vs venturi pumps
| Feature | Peristaltic (flow-based) | Venturi (vacuum-based) |
|---|---|---|
| How it works | Rollers squeeze the tubing; you set aspiration flow (mL/min) and a vacuum limit | Gas creates vacuum directly; you set vacuum; flow follows |
| Vacuum build-up | Only when the tip is occluded | Immediate, even without occlusion |
| Feel | Controlled, good for beginners | Fast attraction, strong followability |
| Examples | Most machines including Alcon Infiniti/Centurion and many Indian machines | Venturi mode on Bausch & Lomb Stellaris, some others offer both |
Typical settings by step (starting points only)
| Step | Power | Vacuum | Aspiration flow | Comment |
|---|---|---|---|---|
| Sculpting (divide and conquer grooves) | Moderate, continuous or pulse | Low (about 50–100 mmHg) | Low to moderate (about 20–25 mL/min) | Low vacuum so the nucleus is shaved, not grabbed |
| Quadrant / chop removal | Pulse or burst, lower | High (about 250–450 mmHg) | Moderate (about 30–40 mL/min) | High vacuum to hold and bring fragments to the tip |
| Epinucleus | Low or none | Moderate (about 150–250 mmHg) | Moderate | Avoid catching the posterior capsule |
| Cortex (I/A) | None | High (about 400–600 mmHg) with a 0.3 mm port | About 30–40 mL/min | Engage cortex under the rhexis, pull centrally |
| Capsule polish | None | Very low (about 5–20 mmHg) | Low | Gentle |
Bottle height or set IOP is usually higher for chopping (e.g. 90–110 cm or the equivalent) and can be lowered for I/A. Values differ widely between machines and tips; your consultant's presets are the reference.
Ultrasound modes
| Mode | Description | Use |
|---|---|---|
| Continuous | Constant power while pedal is in position 3 | Sculpting |
| Pulse | Fixed number of pulses per second with off-time | Quadrant removal; less heat |
| Burst | Single or repeated bursts of fixed duration | Chop, impaling the nucleus |
| Torsional / transversal | Side-to-side tip movement (e.g. OZil) | Better followability, less repulsion and heat |
Watch for wound burn: high power with poor flow (occluded tip, tight wound, kinked sleeve, viscoelastic plugging the tip) heats the incision and can cause a corneal burn. Keep flow going and use pulse or torsional modes.
Before you start: priming and tune
Set-up checks
- Choose the right pack, tip (e.g. 0.9 mm, 30° or 45° bevel) and sleeve for your incision size.
- Prime the tubing and check for kinks, bubbles and leaks.
- Tune (test) the handpiece in the test chamber; fill the chamber completely.
- Check the bottle is full and at the right height (or IOP set), and the drip chamber is visible.
- Confirm the foot pedal positions and the settings for each step with the nurse.
Problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Surge (chamber collapses after occlusion break) | Vacuum too high for the inflow, low bottle, wound leak | Lower vacuum, raise bottle or set IOP, check the wound, use a smaller tip or surge-reducing settings |
| Shallow, unstable chamber throughout | Low bottle, leaking wound, kinked inflow tube, empty bottle | Raise bottle, check tubing and bottle, suture or reduce wound leak |
| Poor followability (fragments do not come to the tip) | Low flow or vacuum, wrong bevel orientation | Increase flow or vacuum; turn the bevel towards the fragment |
| Fragments chatter or bounce away | Too much power, too little vacuum | Lower power, increase vacuum, use pulse or torsional |
| Occlusion alarm with no progress | Tip blocked | Clear the tip with reflux; check aspiration tubing |
| Wound burn | High power with low flow | Stop; restore flow; use less power |
Pearls
- Peristaltic pumps build vacuum only on occlusion: safest for beginners.
- Low vacuum for sculpting, high vacuum for chopping and quadrant removal.
- If the chamber surges, lower the vacuum or raise the inflow before changing anything else.
Common mistakes
- Using chopping vacuum while sculpting, which grabs the nucleus and stresses zonules.
- Ignoring a leaking wound that causes chamber instability.
- High continuous power with an occluded tip (wound burn).
Test yourself: flip cards
Quick quiz
Related: Phacoemulsification Step by Step: A Beginner's Guide, Ophthalmic Viscosurgical Devices (OVDs): Cohesive, Dispersive, Viscoadaptive, Brands, Soft-Shell Technique and Removal, Ophthalmic Blades, Knives and Trocars: Keratome Sizes, Crescent, Side-Port, MVR and Vitrectomy Gauges Explained, Cataract Pre-operative Risk Checklist: Spot the Difficult Case, IOL Injectors and Cartridges for Residents: Alcon A, B, C, D, Preloaded Systems, J&J Unfolder, Zeiss, Medicel and Indian Lenses.
Key sources
- Devgan U. Phaco fluidics and phaco ultrasound power modulations. Ophthalmol Clin North Am. 2006
- Seibel BS. Phacodynamics: Mastering the Tools and Techniques of Phacoemulsification Surgery. 4th ed. Slack; 2005
- Ward MS, Georgescu D, Olson RJ. Effect of bottle height and aspiration rate on postocclusion surge. J Cataract Refract Surg. 2008
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