Cover Focus | Mar/Apr '17

Disassembling a Catarock

A technique for reduced CDE and enhanced safety.

Hypermature cataracts can be a challenge. Significant lens density makes disassembly more difficult, and a posterior plate can compound the problem. Excessive use of ultrasound energy can expose the corneal endothelium to trauma and lead to injury or decompensation. It can also cause corneal wound burn.

Hypermature cataracts usually have very little epinucleus or cortex, resulting in a floppy posterior capsule. Removing the last remaining fragments can be tricky, as a floppy posterior capsule coupled with postocclusion surge is a setup for posterior capsule rupture.

With traditional techniques, the posterior plate is a challenge because it is dangerously close to the posterior capsule, with little to no epinucleus or cortex for protection. The deep and flat position of the plate makes it awkward and precarious for the phaco tip to try and sculpt, suck, grab, or hold lens material with ultrasound and high vacuum. The solution to this dilemma is mechanical fracturing.

TIP

In hypermature cataracts, significant lens density makes disassembly more difficult, and a posterior plate can compound the problem.

I would like to describe a different chopping technique, which emphasizes these principles of mechanical fracturing. The phaco handpiece, rather than acting as a sonicator or aspirator, primarily functions as a chopper. In essence, this is a dual-chopper technique, with the chopper and phaco tip fracturing the lens into smaller pieces without any ultrasound energy or vacuum. This enables precise placement of instruments to chop lens pieces, even in difficult-to-access spaces, for safe and reliable fragmentation.

THE TECHNIQUE

Under irrigation alone, the chopper is placed out to the equator in typical horizontal chopping fashion. The wrist is further supinated to rotate the chopper in such a way that the tip is in a more horizontal position. This allows the chopper tip to support the lens from below and help elevate and hold the lens. The phaco tip is bevel down and tilted into a more vertical position. Using mechanical leverage, the chopper supports from below and the phaco tip is driven into the lens material to break it into two heminuclei. This is the double chop maneuver.1

The chopper is then placed out to the contralateral equator, and with the phaco tip held in the central trough, the chopper is pulled centrally to fracture the contralateral heminucleus. This is the cross chop maneuver.2

The phaco tip and chopper are used to mechanically crush the remaining fragments into bite-sized pieces. Only now is the phaco tip used to emulsify the bite-size pieces using gentle pulses of ultrasound and vacuum. All lens fracturing steps are performed under continuous irrigation with limited use of ultrasound or vacuum. This technique can be performed for all degrees of lens densities and in small pupils.

1. Kim DB. Double-chop: Modified-chop technique eliminating ultrasonic energy and vacuum for lens fragmentation. J Cataract Refract Surg. 2016;42:1402-1407.

2. Kim DB. Cross chop: modified rotationless horizonal chop technique for weak zonules. J Cataract Refract Surg. 2009;35:1335-1337.

author
Brian Kim, MD

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