Fang Sophia Y, DeBoer Charles M T, Humayun Mark S
Eye Concepts, Doheny Eye Institute, 1450 San Pablo Street, DVRC 119, Los Angeles, CA 90033-3699, USA.
Graefes Arch Clin Exp Ophthalmol. 2008 Jan;246(1):61-7. doi: 10.1007/s00417-007-0672-8. Epub 2007 Sep 18.
Despite their clinical advantages, smaller-diameter vitrectomy systems pose significant challenges in vitreous removal. The percentage of time the vitreous cutter port is open while cutting (duty cycle) is one of the primary factors that affect flow. Herein, we examine the effect of duty cycle on the flow performance of new-generation cutters relative to current instrumentation.
Performance of 25-gauge (ga) and 20-ga new-generation spring-return pneumatic cutters (n = 24 and n = 28 respectively) was analyzed relative to current-generation cutters, across their specified cut-speed range under clinical vacuum pressures of 500 mmHg (25-ga) and 200 mmHg (20-ga). A precision balance measured mass of water or porcine vitreous removed from a vial by a cutter; this was recorded in real-time and converted to flow rates. Frame-by-frame analysis of high-speed video was used to determine duty cycle. Data was analyzed using linear regression and the t-test.
Compared with the current-generation, the new-generation cutters exhibit increasingly greater water flow rates at higher cut speeds (P < 0.001). Vitreous flow rates of the new-generation cutters are relatively constant as cut speed increases, and are significantly greater than those of the current-generation cutters at cut speeds of 1500 cuts per minute (CPM) or higher (P < 0.001). The new-generation 25-ga cutter exhibits greater vitreous flow rates at higher cut speeds than the current-generation 20-ga cutter: at 2000 and 2500 CPM, the new 25-ga cutter has 1.45 and 11.88 times the vitreous flow rate of the current 20-ga cutter (P < 0.001) respectively. Duty cycles of the new-generation cutters are significantly higher than those of the current-generation at all cut speeds (P < 0.001).
Although a number of factors influence flow, the high and relatively constant vitreous flow rates of the new-generation cutters are most likely due to their maintenance of high duty cycle as cut speed increases. The findings illustrate that in optimizing duty cycle, the vitreous flow efficiency of smaller-diameter cutters can match or exceed that of larger diameter cutters.
尽管小直径玻璃体切割系统具有临床优势，但在玻璃体切除过程中仍面临重大挑战。玻璃体切割器端口在切割时打开的时间百分比（占空比）是影响流量的主要因素之一。在此，我们研究了占空比对新一代切割器相对于现有器械的流量性能的影响。
相对于现有切割器，分析了25号（ga）和20号新一代弹簧复位气动切割器（分别为n = 24和n = 28）在500 mmHg（25号）和200 mmHg（20号）临床真空压力下其指定切割速度范围内的性能。使用精密天平测量切割器从瓶中吸出的水或猪玻璃体的质量；实时记录并转换为流速。通过对高速视频逐帧分析来确定占空比。使用线性回归和t检验分析数据。
与现有切割器相比，新一代切割器在更高的切割速度下表现出越来越高的水流速（P < 0.001）。随着切割速度增加，新一代切割器的玻璃体流速相对恒定，并且在每分钟1500次切割（CPM）或更高的切割速度下，显著高于现有切割器（P < 0.001）。新一代25号切割器在更高切割速度下比现有20号切割器表现出更高的玻璃体流速：在2000和2500 CPM时，新型25号切割器的玻璃体流速分别是现有20号切割器的1.45倍和11.88倍（P < 0.001）。在所有切割速度下，新一代切割器的占空比均显著高于现有切割器（P < 0.001）。
尽管有许多因素影响流量，但新一代切割器高且相对恒定的玻璃体流速很可能是由于随着切割速度增加其保持了较高的占空比。研究结果表明，在优化占空比时，小直径切割器的玻璃体流动效率可以匹配或超过大直径切割器。
