Key Concepts and Advances in Phaco Power Delivery
The delivery of phaco power can have both favorable and unfavorable consequences. Cavitation, shock waves, shear forces, and heat buildup at the tip may facilitate disassembly of the lens nucleus. However, more power is not necessarily better; the longitudinal stroke of the phaco tip tends to push nuclear fragments away even as the aspiration attracts them, resulting in chatter. In addition, heat buildup from the delivery of phaco power may cause thermal injuries such as wound burns or damage to the corneal endothelium.
Many parameters can be adjusted to deliver phaco power more efficiently and safely. The size and angle of the phaco tip can be altered to increase cutting efficiency. Intermittent rather than continuous phacoemulsification modes, such as pulse and burst, can also be used. Various mechanical strategies, including torsional and elliptical movement of the phaco tip (rather than only longitudinal movement), may also minimize heat generation.
Phaco tips vary by angle and size of the lumen. Phaco tips are available with bevels of 0°, 15°, 30°, 45°, and 60° (see Fig 8-1). The surgeon generally chooses the bevel angle of the phaco tip according to personal preference. A tip with a steeper bevel has an oval port with a larger surface area, which can generate more holding force (Fig 8-2) and greater cutting efficiency. The disadvantage of steeper bevels is that the larger opening may be more difficult to occlude to achieve full vacuum. End configurations can be round, ellipsoid, bent, or flared.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.