Phacoemulsification Time Determinants and Modifiers
Narrative Responses:
Purpose
The length of phacoemulsification time has recently gained interest with the introduction of femtosecond cataract lasers. The problem with the comparisons to date is that un-adjusted times are misleading. We know surgical style and technique is a determinant but other factors are not well recognised.
Methods
Clinical and machine parameters were collected prospectively for 250 cataract operations by one surgeon. The patient age and grade of nucleus sclerosis were recorded preoperatively, at surgery irrigation, vacuum and aspiration were fixed for all cases, phaco emulsification power was allocated to 10% increments from 30 to 60% using a standard burst torsional mode for each surgical session. A range of different phaco needles were used on a sessional basis. All cases were divide and conquer technique Following cataract surgery the total ultrasound time, average % power, and aspiration fluid volume were recorded.
Results
Patient age determines the lens weight and was correlated with increased ultra sound time (r2=0.11) and aspiration volume (r2=0.14). Both time and aspirate volume increased the with cataract density, but in a nonlinear fashion, denser cataracts required proportionately more power. Time reduced from an average 20.42 secs at 30% power to 13.33 secs at 60% power, but this varied between needles although all produced less time with more power.
Conclusion
Age modifies the ultrasound time because the lens weight increases yearly (by 12% from 60 to 80 years), density of nucleus sclerosis also modified ultrasound time. The power setting was an important determinant, along with the type of needle used in surgery.