Two-speed phacoemulsification for soft cataracts using optimized parameters and procedure step toolbar with the CENTURION Vision System and Balanced Tip

Abstract

Purpose: To present a cause of posterior capsule aspiration and a technique using optimized parameters to prevent it from happening when operating soft cataracts.

Patients and methods: A prospective list of posterior capsule aspiration cases was kept over 4,062 consecutive cases operated with the Alcon CENTURION machine and Balanced Tip. Video analysis of one case of posterior capsule aspiration was accomplished. A surgical technique was developed using empirically derived machine parameters and customized setting-selection procedure step toolbar to reduce the pace of aspiration of soft nuclear quadrants in order to prevent capsule aspiration.

Results: Two cases out of 3,238 experienced posterior capsule aspiration before use of the soft quadrant technique. Video analysis showed an attractive vortex effect with capsule aspiration occurring in 1/5 of a second. A soft quadrant removal setting was empirically derived which had a slower pace and seemed more controlled with no capsule aspiration occurring in the subsequent 824 cases. The setting featured simultaneous linear control from zero to preset maximums for: aspiration flow, 20 mL/min; and vacuum, 400 mmHg, with the addition of torsional tip amplitude up to 20% after the fluidic maximums were achieved. A new setting selection procedure step toolbar was created to increase intraoperative flexibility by providing instantaneous shifting between the soft and normal settings.

Conclusion: A technique incorporating a reduced pace for soft quadrant acquisition and aspiration can be accomplished through the use of a dedicated setting of integrated machine parameters. Toolbar placement of the procedure button next to the normal setting procedure button provides the opportunity to instantaneously alternate between the two settings. Simultaneous surgeon control over vacuum, aspiration flow, and torsional tip motion may make removal of soft nuclear quadrants more efficient and safer.

Keywords: INFINITI Vision System; cataract surgery; complication; divide and conquer; posterior capsule CENTURION Vision System.

Figure 1

The machine panel display of the Quadrant Removal Setting (Quadrant Removal Step Button enlarged) in the procedure step toolbar shows a −2 vacuum rise with linear control (angled line) of torsional amplitude. Notes: Vacuum and aspiration flow parameters are fixed (horizontal line) with moderate value maximums for foot position 2 (left side of vertical line) and 3 (right side of vertical line). A target IOP of 55 mmHg is the equivalent of a gravity feed bottle height of 75 cm and has been selected for all three foot positions. The iP (Intelligent Phaco) feature is engaged with 10 msec longitudinal pulse duration, 95% vacuum threshold, and 1.0 longitudinal/torsional ratio. Abbreviation: IOP, intraocular pressure.

Figure 2

Video freeze frames from standard slow motion 30 frames/second video show the posterior capsule aspiration event. Notes: At 0 seconds (top left) the tip aperture has just made contact with the edge of the quadrant. Torsional tip motion, vacuum, and aspiration flow are all active in foot position 3 and have already achieved high values. At 0.10 seconds (top right) nuclear material has started to be aspirated through the tip’s aperture which is facing the peripheral posterior capsule but is well away from it. Early dimpling of the outer nuclear rim is occurring as the entire quadrant thickness is being drawn centrally by the vortex of relatively high vacuum and flow projecting from the tip aperture. At 0.20 seconds (bottom left) the full thickness of the quadrant has been aspirated into the aperture, and behind it a plug of cortex and posterior capsule as well. Nuclear material is still being drawn into the tip from the left and right. A faint outline of a punched out hole in the posterior capsule can be seen below the word “Phaco” on the display. The tip aperture is approximately 1.5 mm from the capsule. Maximum vacuum (400 mmHg) has not been reached but aspiration flow and torsional values have remained high. At 0.30 seconds (bottom right) the hole in the cortical layer and posterior capsule is more easily seen. The remaining posterior capsule and surrounding cortex and peripheral nucleus have been released and have already been drawn back into their normal positions by zonular traction. Abbreviations: IOP, intraocular pressure; Vac, vacuum.

Figure 3

Video freeze frame of third quadrant removal. Notes: At 6.8 seconds, the third quadrant has been acquired and phacoemulsification continues to be carefully accomplished while trying to stay away from the capsular defect. There was enough aqueous in front of the anterior hyaloid membrane so that it was insulated from being aspirated. Abbreviations: Vac, vacuum; IOP, intraocular pressure.

Figure 4

The machine panel display of the Epinucleus Removal Setting (Epinucleus Removal Step Button enlarged in the procedure step toolbar) shows linear control of vacuum and aspiration flow in foot position 2, which becomes fixed at their maximums in foot position 3 when linear control of continuous torsional amplitude becomes available. The iP feature is engaged but does not come into play in soft cataracts. The Epinucleus Removal Setting procedure step button is between the Sculpt and Quadrant Removal procedure step buttons in the procedure step toolbar along the bottom of the display. Abbreviation: IOP, intraocular pressure.

Figure 5

The machine screen display of the Sculpt Setting (Sculpt Procedure Step Button enlarged in the procedure step toolbar) shows low fixed values for vacuum and aspiration flow and linear control of continuous longitudinal tip motion. Note: These parameters provide just enough vacuum and flow to aspirate the mix of nuclear dust in balanced salt solution. Abbreviation: IOP, intraocular pressure.

Figure 6

Soft cataract technique using the Epinucleus Removal Setting. Notes: Top Left shows the Balanced Tip is turned slightly obliquely (aperture away from the surgeon) so that better visualization of its distal edge on the posterior nuclear plate is available. Deeper sculpting is more safely accomplished with this improved view. At 0 seconds (top right) the quadrants have been separated and their deeper corners shaved away. The aperture of the obliquely oriented tip (aperture towards the surgeon) is just becoming occluded as 7% torsional power is beginning to be used. With aspiration flow at 20 mL/min, vacuum is starting to build as the cyclodialysis spatula pushes the adjacent quadrant away, thus opening a space for the left edge of the first quadrant to roll through. If sudden occlusion break and excessive aspiration were to occur, the tip would break through the left edge of the quadrant and be in a free space and not break through to the posterior capsule. 0.92 seconds later (bottom left), the tip and the left edge of the attached quadrant are being drawn centrally by high vacuum while the tip burrows into the quadrant’s substance. At 1.42 seconds, (bottom right) adhesion is maintained by low torsional motion which creates a continuous new surface to which the tip can bond with high vacuum. The tip aperture and the left half of the first quadrant have been centralized. Maximum vacuum has been achieved reducing flow to zero for this instant, but increasing torsional movement will break the occlusion allowing flow of nucleus into the aperture. Abbreviations: IOP, intraocular pressure; Vac, vacuum.

Figure 7

Removal of the second and subsequent quadrants of relatively firm soft lenses using the Quadrant Removal Setting. Notes: With the timer set at 0 seconds (left) the second quadrant is about to be engaged using the quadrant removal setting. 0.52 seconds (right) later the tip aperture and second quadrant have been centralized. Nuclear material is being aspirated with high vacuum, intermediate aspiration flow, and minimal torsional tip movement. Abbreviations: IOP, intraocular pressure; Vac, vacuum.