Cataract Surgery Focus on Phaco Systems

We cataract surgeons and our patients continue to benefit from ongoing improvements in phaco technology. Because cataract surgery is already such a fast and efficient operation, we are primarily interested in new technologies that can expand our margin of safety—particularly in eyes with dense nuclei and weak zonules. Historically, our three main safety-related concerns with phacoemulsification have been (1) thermal damage to the incision, (2) endothelial trauma associated with prolonged ultrasound time, and (3) capsular rupture due to postocclusion surge. Incision burns are most likely to occur with the higher power levels and prolonged ultrasound times needed for brunescent lenses. Increasing the stroke length of the vibrating phaco tip generates more frictional heat as well as more phaco power. The thicker nuclear emulsate can admix with a highly retentive ophthalmic viscosurgical device (OVD) to form a viscous plug that clogs the phaco tip or aspiration line. If fluid outflow is blocked, then the gravity-fed inflow of irrigation also ceases. With neither the inflow nor the outflow of fluid to cool it, a phaco tip in continuous mode will instantaneously burn the cataract incision. The loss of endothelial cells is also much greater with brunescent nuclei, the size and density of which require increased phaco time and energy for emulsification compared with standard cataracts. In my opinion, it is the increased particulate turbulence occurring with brunescent nuclear fragments that causes the most damage to endothelial cells. Rigid nuclear pieces drawn by aspiration to the phaco tip do not mold and conform as well to its opening. This and the added stroke length of higher ultrasound power settings increase the chatter and turbulence of nuclear particles within the anterior chamber. Finally, there are several reasons why posterior capsular rupture is more common with rock-hard nuclei. The added rigidity and girth of the nucleus more directly transfers instrument-related forces to the capsule and zonules, and there is far less of an epinuclear shell to cushion the movements of the endonucleus. We typically maximize vacuum levels to improve holding power in these cases, but this increases the risk of postocclusion surge. A lax posterior capsule due to weak or deficient zonules will trampoline more easily toward the phaco tip, making even a minor or momentary degree of surge precarious. Fortunately, all three major manufacturers provide us with bona fide advances in their latest machine platforms that address the three problems I have outlined. This article highlights specific safety features that users of the Whitestar Signature System (Advanced Medical Optics, Inc., Santa Ana, CA) should understand and deploy.