Anterior chamber maintainer adequate for micro surgery

By Roibeard O'hÉineacháin

NICE - Micro-incision cataract surgery is now possible with AMO WhiteStarTM phacoemulsification system technology, a UK ophthalmologist told the XX ESCRS Congress.

Richard Packard MD reported that he has been able to safely and successfully remove a cataract through a 1.0 mm incision using the WhiteStar system - an upgrade on the Soverign phacoemulsification system.

The advantages of the micro-incision approach include a more rapid visual rehabilitation and the prevention of induced astigmatism. Furthermore, it allows surgeons to take advantage of new IOLs that can be inserted through the unenlarged micro-incisions, he added.

Dr Packard uses a bimanual technique to perform the micro-incision procedures. He inserts the phacoemulsigication needle through one 1.0 mm incision and an irrigating chopper through a second 1.2 mm incision.
"Although various attempts have been made to do bare needle phacoemulsification, the biggest problem has been wound cooling which is necessary throughout surgery with conventional phacoemulsification.

"WhiteStar and SonolaseTM on the Sovereign phacoemuslification system have changed all that," Dr Packard said.
Unlike standard continuous burst phacoemulsification, WhiteStar technology breaks the phacoemulsification stream into very rapid pulses, consisting of adjustable ultrasound bursts followed by adjustable rests, he explained.

As a result there is a decrease in build-up heat at the tip and a reduced repulsive force of phacoemulsification tip.
Therefore, during sculpting a surgeon only needs to use 700 m/s total bursts per second compared to a continuous burst of 1,000 m/s/s with conventional phacoemulsification.

Furthermore, during quadrant removal, the surgeon can spread out the pulses between longer rest times and have for example 200 m/s total burst per second, he continued.
"The effect is to produce efficient phacoemulsification with low heat production and enhanced followability due to diminished tip bounce at all times.
"In addition, the tight incisions also provide enhanced fluidics with minimal leakage and greater stability of the anterior chamber. Here now is a technology that would allows the safe use of micro-incisions," he said.

Nonetheless, Dr Packard noted that he encountered a couple of problems with his first two cases. The first problem involved performing capsulorhexis through a 1.0 mm incision.

"I stopped doing a full-needle capsulorhexis back in the late 80s and I've been using forceps since so it was either a question of re-learning how to use the needle or finding some forceps to do the capsulorhexis through a micro-incision. To that end we now have a co-axial rhexis forceps," Dr Packard said.
In addition, there was a considerable amount of spray from the phacoemulsification needle, particularly the hub. Dr Packard noted that in conventional phacoemulsification, the sleeve covering the needle prevents the spray.

To prevent it when using a sleeveless technique, he now places the phacoemulsification sleeve hub normally and then tears the sleeve off.
Dr Packard also had to make some adjustments with the configuration of the system's fluidics. To correct inadequate irrigation, he now uses an instrument with more than 40cc minute flow used for irrigating and the bottle is raised.

In addition, to prevent siphoning from the irrigation outlet on the handpiece, he now places a plastic syringe cap on the top of the outlet.
Finally to make the technique bi-manual, Dr Packard developed an irrigating chopper. The device consists of an irrigation probe with a sharp tip for chopping that is perpendicular to the axis of the probe.

Furthermore, a Kelman style curved phacoemulsification needle is used because it enhances the ability to manoeuvre the nucleus.
"The advantage is that one is cross chopping because of the position you have to use for your bi-manual surgery. I use a forceps to insert the chopper through a 1.2 mm incision.

"Now I impale with my right hand and while holding with my right hand, I actually move the chopper cut into the nucleus and move away to the left. You can then can repeat this as the chamber remains stable at all times," Dr Packard noted.
He added that the recent and ongoing development of IOLs which can be inserted through incisions less than 1.5 mm should really bring micro-incision phacoemulsification into its own as a routine procedure.

Moreover, even when implanting a conventional IOL after micro-incision phacoemulsification, surgeons will have the option of creating a new incision for an IOL insertion as an astigmatic tool to treat any pre-existing cylinder, he pointed out.

"WhiteStar has given us safe micro-incision surgery. The wound burn has disappeared and post-occlusion surge has already been dealt with by the fluidics on the Soverign System. This means that this surgery is possible for those who use the Sovereign just by upgrading their system," he said.

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