Cataract surgeons desire equipment and techniques that deliver safety and efficiency. Advanced fluidic systems within the phacoemulsification platforms continue to grow in sophistication. As we have gained experience with these platforms, we are realizing that traditional fluidic parameters and machine settings may no longer be necessary. Surgeons are now able to use lower infusion pressures and higher vacuum levels to deliver excellent patient outcomes with an increasingly predictable experience.

The Past

Previously, surgeons were required to maintain a very high intraocular pressure (IOP) to maintain chamber stability. Intraocular pressure levels were not discussed in detail in the era of gravity-fed systems. Surgeons and equipment manufacturers focused on the “bottle height” at the various steps of the cataract procedure. It was not uncommon, however, for surgeons to desire bottle heights that led to intraoperative IOP levels in the 65 mmHg to 85 mmHg range. The elevated IOPs used at the time of surgery, while transient, represented a significant departure from baseline IOP for every patient. In the quest for ultimate chamber stability, this surgical environment led to a relative “hyperinflation” of the eye. Just by turning on irrigation, the intraocular structures were impacted with stretching of the sclera, pupil dilation, and posterior movement of the lens-iris diaphragm. Although the typical cataract surgeon is not visualizing the optic nerve and retinal vascular perfusion at the time of surgery, these certainly could be impacted at the time of surgery with such high IOP.

Even in the early days of phacoemulsification, astute surgeons like Robert Osher, MD, demonstrated there may be a better approach—one involving the use of fluidic parameters that included lower infusion pressures.¹

The Present

Advanced fluidic systems now allow a focus on IOP at the time of surgery. Machines focus and modulate fluidics to maintain a set IOP throughout the case. Chamber stability is maintained, and efficient surgery can be conducted at IOPs as low as 28 mmHg.^2,3 This environment has less visible impact on the intraocular structures. There are less visible impacts on the pupil. The lens-iris diaphragm remains in a more normal anatomic state (Figure 1). Surgical efficiency is not impacted. In fact, in certain cases reverse pupillary block is mitigated or even eliminated.

As phacoemulsification platforms advance, many surgeons are recognizing the advantage of using a more physiologic IOP during surgery. Emerging evidence shows that lower infusion pressures are associated with less impact on corneal health and less early postoperative anterior chamber inflammation.^2,4 Furthermore, studies indicate that lower infusion pressures lead to less discomfort at the time of cataract surgery.⁴

Advice for Adoption

We have found that the migration to lower IOPs can be accomplished with great efficiency.² Furthermore, the transition to lower infusion pressures does not require adjustment in other fluidic parameters, including vacuum or aspiration flow rate. Our advice to surgeons would be to operate at incrementally reduced infusion pressures. We have found small reductions in IOP (ie, 5 mmHg) to often be imperceivable. Performing an increasing number of cases at the lower target IOP will bring confidence and comfortability to further reduce operating infusion pressures. As always, final parameters and final IOP will be surgeon specific, with dependence on patient anatomy, technique, and surgeon preference.

Impact for Patients

There must be additional study on the impact of lower infusion pressures on the glaucoma patient population. Theoretically, more physiologic infusion pressures should be of great
benefit to optic nerve health. However, we must recognize that the elevated IOPs associated with surgery are transient in nature. Even though our retina colleagues can directly visualize the impact of IOP on retinal perfusion during procedures like pars plana vitrectomy, more detailed study into the long-term impact on retinal and optic nerve physiology is warranted with all intraocular procedures.

We have not noted any differences in intraocular pressures in the postoperative period in patients undergoing cataract surgery using low vs high IOP. In our paired-eye studies where 1 eye received surgery at an IOP of 28 mmHg and the fellow eye received surgery at an IOP of 65 mmHg, the postoperative IOPs were the same at day 1, day 7, and month 1. (These data have not yet been published). This indicates that viscoelastic removal at the end of the case is similar regardless of the IOP setting used at the time of surgery.

Many surgeons today are combining cataract surgery with MIGS procedures. Many of these procedures were initially studied in the setting of  platforms using higher infusion pressures. Will lower infusion pressures impact the intraoperative experience for the surgeon or anticipated postoperative observations? Anecdotally, others have noted enhanced blood reflux into the anterior chamber with some MIGS surgeries completed with more physiologic pressures when the viscoelastic is removed near case completion. Could higher infusion pressures lead to a more robust “washout” of blood from Schlemm’s canal and other downstream vasculature? Again, additional study is indicated.

The Future

In many ways, we are in the era of new thought processes when it comes to cataract surgery. We now have a renewed focus on making a great procedure even better by attempting to complete the procedure with even less impact on the eye. As we move forward, our surgeries will be performed at lower infusion pressures, using less balanced salt solution, with less energy use. These philosophic adjustments in our thinking are leading to a less invasive cataract surgery—a surgery that will offer faster recovery and enhanced experience. Taking advantage of today’s technology and technology on the horizon will lead to a more physiologic and better procedure. GP

Matthew P. Rauen, MD, is a cataract, cornea, and refractive surgeon at the Wolfe Eye Clinic in West Des Moines, Iowa. He reports consultancy to Alcon Laboratories. Dr. Rauen can be reached at MRauen@wolfeclinic.com.

References

1. Osher RH. Slow motion phacoemulsification approach. J Cataract Refract Surg. 1993;19(5):667. doi:10.1016/S0886-3350(13)80025-9

2. Rauen MP, Joiner H, Kohler RA, O’Connor S. Phacoemulsification using an active fluidics system at physiologic vs high intraocular pressure: impact on anterior and posterior segment physiology. J Cataract Refract Surg. 2024;50(8):822-827. doi:10.1097/j.jcrs.0000000000001457

3. Suzuki H, Igarashi T, Takahashi H. Effect of a new phacoemulsification and aspiration handpiece on anterior chamber stability. J Cataract Refract Surg. 2023;49(1):91-96. doi:10.1097/j.jcrs.0000000000001071

4. Scarfone, HA, Rodriguez EC. Evaluation of early changes of the anterior vitreous interface after cataract surgery, using low-pressure settings determined by OCT. Presented at: American Society of Cataract and Refractive Surgery (ASCRS) annual meeting; May 5-8, 2023; San Diego, California.