Phaco Methods and Device SettingsI

The main four phacoemulsification - methods / techniques you will have to learn are:

“As a phaco-surgeon you first need to be able to handle the divide and conquer technique, later the three other phaco-methods”.

If you feel confortable with divide and conquer, then you may start with the other techniques.

Use different phaco programs for different situations during phaco surgery. Three phaco programs should actually be enough to perform the 4 main phaco techniques.

You have to know very well your phaco machine in order to adapt the device settings for yourself. Try while coming from the safe side…

3 Phaco-Program examples (for Whitestar Phaco Machine, AMO (Abbott Medical Optics)):

You do not have to take over these settings. Use the safest settings in your hands, but something must happen while you are working in the eye. Too safe settings will increase your working time in the eye…

Phaco-1 program: for grooving and sculpting the nucleus. Continuous phaco power.

For chopping you need high vacuum power in order to hold the lens. Therefore you may need to adapt the settings.

Phaco-2 program: for dealing with the smaller pieces of the nucleus. Non-continuous phaco power.

Phaco-3 program: like Phaco-2, but safer… Non-continuous phaco power.

To sculpt the nucleus you need low outflow rate and just little vacuum.

High outflow rate does not increase the speed of nucleus removal, but rather creates turbulence and high flow rate through the eye and since you are not occluding the phaco tip, you can use low vacuum while grooving.

If cataract surgeons talk about flow, they generally mean the outflow rate while the pump is operating. This is measured in ml per minutes.

The outflow rate is the flow rate at which the fluid leaves the eye through the aspirating instrument (ml/Min).

Remember: the bottle height has no influence on the outflow rate in peristaltic pumps (in Venturi pumps there is a relationship: the higher the pump, the higher the flow…).

The bottle height has to be adapted to the flow since the chamber should stay stable during work.

A low bottle and a high flow will lead to a collapsed anterior chamber.

The outflow of fluid cools down the phaco tip while working. Using only the phacoemulsification mode will create a corneal burn…

While sculpting a hard nucleus you should increase the outflow rate in order to cool down the phaco tip.

A decreasing IOP will manifest as a shallowing of the anterior chamber, but there are of course other reasons for a shallow anterior chamber (we will see that later)…

The infusion bottle height will tell you the IOP if the incisions are tight and you are not operating the pump. The 15 cm bottle height corresponds to 11 mmHg, roughly 15 cm = 10 mmHg.

As soon as you use the operating pump, fluid will flow out of the eye and the IOP will lower down. Look at the anterior chamber depth while working in the eye. You may have to adapt the bottle height.

Vacuum is building up when the phaco tip is occluded. You do not have a vacuum effect without occlusion… (Figure 1).

Vacuum is not flow rate! The flow rate will just tell you how fast the vacuum will build up in an occluded tip. The higher the flow, the faster you will build up vacuum (Figure 1).

Vacuum is not important while sculpting the nucleus, but gets important if you are eating the lens pieces. That's why some surgeons have two or more programs of vacuum and pump action during one phaco.

For a given amount of ultrasound power per time unit, more volume of nuclear material will be aspirated while the tip is occluded. Therefore using occlusion during phaco is more time and energy efficient then without occlusion.

To hold a piece of nucleus you need high vacuum. First grab it with aspiration and create a short phaco power in order to get into the piece and create tip occlusion for vacuum.

Ultrasound power creates a repulsive action meaning that the aspirated piece is also pushed away during phaco action. This repulsive phaco action has to be overcome by adequate vacuum power in order to keep the piece at the tip.

If you want to attack a piece of nucleus, you have to turn the tip's opening towards the piece in order to rapidly create an occlusion. Therefore you have to be aware of your tip angle (Figure 2).

Do not press with the phaco tip on the incision. Compression of the incision lips with the working phaco tip will create a corneal burn. Especially the anterior lip is in danger while sculpting deep.

As soon as you have vacuum building up, you know then that you have occluded the tip. But be aware of the fact that you will then not have flow cooling the phaco tip…

Do not use phaco power for long time otherwise you have a corneal burn.

If the anterior chamber is flattening during cataract operation, then stop all maneuvers in the eye, calm down and think about the reason. You may deal with a subchoroidal hemorrhage/ effusion, or an infusion misdirection syndrome (fluid passing through the zonula or a capsular tear which then accumulates in the retrocapsular space), or an instable anterior chamber due to inadequate infusion pressure or leaky incisions, or fluid misdirection under the iris plane in floppy iris syndrome or myopic eyes. A lot of “or's” (Figure 3).

The term “positive vitreous pressure” is a descriptive and not a diagnostic term. It just means that the anterior chamber is flattening… You will have to find out why (Figure 3).

If the anterior chamber is flattening during cataract operation you have to pressurize the eye to normal or slightly elevated intraocular pressure. If the anterior chamber remains shallow you deal with either a subchoroidal hemorrhage/effusion or more often an infusion misdirection syndrome. If the anterior chamber deepens again check the infusion bottle, the infusion line and the incisions (Figure 3).

A flat anterior chamber with normal IOP is usually due to an infusion misdirection syndrome. If the media are clear and you can exclude a subchoroidal hemorrhage/effusion, then continue the cataract operation with lower infusion bottle. You may have to convert to ECCE.

If you diagnose a subchoroidal hemorrhage/effusion during cataract operation, immediately pressurize and close the eye.