We would like to thank Mayer and associates for describing reduction of ultrasound energy with femtosecond laser phacofragmentation. However, the authors’ methodology is ambiguous and may ignore the contribution of torsional power during phacoemulsification.

Mayer and associates used the Infiniti Vision System (Alcon, Inc, Ft. Worth, Texas, USA). Ambiguity results because the Infiniti Metrics Display does not provide Effective Phaco Time (EPT). Rather, it provides Phaco Time, defined as the “total time phaco power was active,” and 2 metrics of phaco power, “Average Phaco Power” and “Average Phaco Power in Position 3.” Average Phaco Power is defined as “Average phaco power over time when phaco power was applied. For example, if Ultrasound Burst mode was selected and 100 mS burst pulses at 70% stroke were generated once a second, the Average Power would record 70%.” Average Phaco Power in Position 3, on the other hand, represents “Average phaco power over time when phaco power was applied in foot pedal position 3. This takes into account the U/S modulation aspects, resulting in a significantly lower reading than Average phaco power. For example, if Ultrasound Burst mode was selected and 100 mS burst pulses at 70% stroke were generated once a second, the Average Power in Position 3 would record 7%.”

It is unclear whether Mayer and associates used Average Phaco Power or Average Phaco Power in Position 3. If they used any modality other than Continuous Phaco, the latter would have been more appropriate. The authors’ “divide and conquer” combination of sculpting, cracking, and quadrant removal might have involved multiple power modulations, which would further suggest the use of Average Phaco Power in Position 3 as the more appropriate metric.

Any contribution of torsional power in the authors’ methodology may have been neglected if they used the OZil modality. In January 2006, Alcon Surgical incorporated OZil torsional technology into the Infiniti Vision System. Other authors who have written about ultrasound reduction after femtosecond laser phacofragmentation have referred to Cumulative Dissipated Energy (CDE). CDE represents the “Total U/S energy in footpedal position 3 (both phaco and torsional) calculated as: (Phaco Time × Average Phaco Power) + (Torsional Time × 0.4 × Average Torsional Amplitude).”

In general, metrics for ultrasound phacoemulsification such as percentage phaco power, EPT, and CDE remain proprietary and unique to each manufacturer, much as they were over a decade ago, when it was written that “Although outcomes such as slit lamp examination and visual acuity may be fairly represented as comparative, we caution against using EPT and average power for drawing conclusions about the relative efficiency of different phaco machines…. Because manufacturers may use different algorithms to calculate these quantities, comparison among different machines remains fraught with difficulty.”

With the increasing utilization of reduction in ultrasound energy as a means to compare the effectiveness of various femtosecond laser phacofragmentation platforms, it is imperative that authors pay scrupulous attention to the definitions of the language that they use.