AN OBJECTIVE COMPARISON OF VITREOUS CUTTERS: HOW FAST IS A "HIGH SPEED" CUTTER?

Carl C. Awh (Nashville)

Objective: An objective flow-rate comparison of three types of vitreous cutters: (1) 20-gauge pneumatic, (2) 20-gauge "high speed", and (3) 25-gauge "high speed".

Purpose: To demonstrate a clinically relevant, reproducible method for testing vitreous cutter flow rates and to compare the flow rates of different types of vitreous cutters.

Methods: A pressurized test chamber containing pig vitreous was used to calculate the flow rate of three different vitreous cutters, using the Bausch & Lomb Millennium vitrectomy unit. Cutters compared were: (1) a standard 20-gauge pneumatic cutter, (2) a "Lightning" 20-gauge vitreous cutter, and (3) a 25-gauge high speed vitreous cutter. Flow rate was defined as the volume of vitreous removed over time, using typical settings of vacuum and cut rate. Infusion pressure was maintained at 50 mmHg.

Results: The 25-gauge cutter, at settings of 500 mmHg and 1500 cpm, had an average flow rate 40 % greater than the conventional pneumatic cutter, at settings of 250 mmHg and 750 cpm. This difference was not statistically significant (p =0.18). The 20-gauge "Lighting" cutter, at settings of 250 mmHg and 750 cpm, had an average flow rate 88 % greater than the pneumatic cutter at the same settings (p=0.0009). At settings of 250 mmHg and 1500 cpm, the 20-gauge "Lightning" cutter had more than double the flow rate of the conventional vitreous cutter (p<0.0001).

Conclusions: Despite smaller diameter probes and tubing, "high speed" vitreous cutters demonstrate flow rates equal to or greater than conventional pneumatic cutters in a laboratory setting. This suggests that "high speed" cutters, which have faster cut rates and theoretical safety advantages, remove vitreous more quickly than conventional pneumatic cutters in a clinical setting.


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