Eyeworld

4 Evolving technology and outcomes in cataract and refractive surgery the "reach" of the needle—its range of attraction—is greater with higher flow rates. Higher levels of flow also overcome turbulence in the anterior cham- ber. Vacuum, on the other hand, establishes hold on material to the tip of the needle —the higher the vacuum, the more efficient the hold. This hold then allows power to be transferred from the tip to the fragment. Higher levels of vacu- um overcome repulsion and reduce chatter. Vacuum is also useful for removing nuclear and cortical material. Softer material can be removed in some cases without phaco power. The higher the vacuum, the more effectively this force can remove material. Denser material requires more power to remodel or remove the material. Vacuum is a force, the effort that is generated to pull the fluid from here to there. When the needle is unoccluded, flow tells us how quickly the fluid is moving from point to point. When the needle is occluded, vacuum is the force necessary to restore that flow. Flow is the action of material in the anterior cham- ber before the material reaches the needle, everything you see happening as the material moves to the needle is flow. Once the needle is occluded— when the material is at the tip— that's vacuum. These two things are always happening at the same time and do not occur in iso- lation from each other; rather, they are synergistic. Flow will bring material to the tip—the higher the flow, the faster the draw. In other words, duced into the technique, video is critical to separate those problems due to the change in technique from those that are coincidental but unrelated. Underlying the opportunity for improvement is a deeper understanding of the available options. Differences in vacuum pump technology, for example, can be utilized to improve var- ious stages of surgery. Under- standing these subtleties may help provide that breakthrough. Breaking down flow vs. vacuum The effect of vacuum is the force created to pull fluid into the lumen of the phaco needle. The type of pump used to cre- ate vacuum doesn't determine the magnitude of the vacuum, but rather how flow is controlled in its relationship to vacuum. The pump is controlled by software, driven by a computer, and ultimately controlled by your foot pedal. So what is the difference between flow and vacuum? Fluid going from one place to another is flow. Flow is a rate—how fast the fluid goes from here to there. We are all familiar with flow, whether it is a slow drip from a garden hose or an explosive jet from a fire hose. The difference between the flow we observe daily and the flow rate in phaco is that the flow we generally observe is not directed. Flow in phacoemulsification is directed into the lumen of the phaco needle, hence the alternative term aspiration, or aspiration rate. A surgical technique is an amalgam of hab- its, available technol- ogy, and instrument familiarity. With this in mind, how does one advance his or her own surgical performance? The first step is to set your ego aside as you take inventory of your existing technique. We all have assumptions that we make about our surgery, and those assumptions may or may not stand up to review. The next step is to estab- lish a measurable goal. Reduc- ing the number of unplanned vitrectomies or reducing case times are relatively simple but highly worthwhile goals. To do this, achieving certain other goals may become necessary, such as improving chamber stability. While metrics alone can be helpful in establishing the suc- cess of a particular change, vid- eo recording of these cases will speed the progress. Video can reinforce the improvements, but will also unmask all of the flaws. As changes are intro- Steven Dewey, MD Improving outcomes, safety, and efficiency with phacoemulsification Steven Dewey, MD, Colorado Springs Eye Clinic, Colorado Springs, Colorado " Underlying the opportunity for improvement is a deeper understanding of available options. Differences in vacuum pump technology, for example, can be utilized to improve various stages of surgery. " –Steven Dewey, MD

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