Prata J A, Mérmoud A, LaBree L, Minckler D S
Department of Ophthalmology, University of Southern California School of Medicine, Los Angeles, USA.
Ophthalmology. 1995 Jun;102(6):894-904. doi: 10.1016/s0161-6420(95)30937-2.
To determine pressure-flow characteristics at physiologic flow rates in vitro and in vivo in rabbits for Ahmed, Baerveldt, Krupin disk, and OptiMed glaucoma implants. The Molteno dual-chamber implant also was evaluated in vivo only.
Five samples of each glaucoma implant were studied. Baerveldt implants were ligated partially for in vitro testing. Opening and closing pressures in air or after immersion in balanced salt solution or plasma were evaluated for the valved devices (Ahmed and Krupin). Pressures were measured in vitro and in vivo in normal rabbits at flow rates preset at between 2 and 25 microliters/minute after the tubes were connected to a closed manometric system. In vivo measurements were made 24 hours after implantation. Resistance to flow was calculated using Poiseuille's equation after at least three separate flow rate readings.
In air, the Ahmed and Krupin valves had opening pressures of 9.2 +/- 3.4 and 7.2 +/- 0.6 mmHg and closing pressures of 5.2 +/- 0.9 and 3.9 +/- 1 mmHg, respectively. Neither opening nor closing pressures could be determined when Ahmed and Krupin valves were immersed. In vitro, the Ahmed and OptiMed devices had higher pressures than did other devices at a 2-microliters/minute flow rate of balanced salt solution. During perfusion with plasma, only the OptiMed device maintained higher pressures than with balanced salt. With all devices, pressures fell rapidly to zero after flow was stopped. The OptiMed device demonstrated the highest resistance values. In vivo, the Ahmed device provided pressures of 7.5 +/- 0.8 mmHg and the OptiMed device gave pressures of 19.6 +/- 5.6 mmHg at a 2-microliters/minute flow rate. After 15 minutes of flow shutdown, the OptiMed implant maintained pressures of 7.1 +/- 1.1 mmHg. The Baerveldt (nonligatured), Krupin, and Molteno dual-chamber implants had similar resistances and pressures in vivo. Pressures with all devices in vivo fell rapidly to zero after conjunctival wound disruption.
Neither the Ahmed nor Krupin devices had demonstrable opening or closing pressures when tested in vitro immersed in balanced salt solution or plasma. With all devices, pressures were higher in vivo than in vitro due to tissue-induced resistance around the explant. Both Ahmed and Krupin valves functioned as flow-restricting devices at the flow rates studied, but did not close after initial perfusion with fluid.
测定Ahmed、Baerveldt、Krupin盘式和OptiMed青光眼植入物在兔体内外生理流速下的压力-流量特性。Molteno双腔植入物仅在体内进行了评估。
对每种青光眼植入物的五个样本进行研究。Baerveldt植入物部分结扎用于体外测试。对带瓣膜的装置（Ahmed和Krupin）在空气中或浸入平衡盐溶液或血浆后的开启和关闭压力进行评估。在将管子连接到封闭测压系统后，在正常兔体内外以2至25微升/分钟的预设流速测量压力。植入后24小时进行体内测量。在至少三次单独的流速读数后，使用泊肃叶方程计算流动阻力。
在空气中，Ahmed和Krupin瓣膜的开启压力分别为9.2±3.4和7.2±0.6 mmHg，关闭压力分别为5.2±0.9和3.9±1 mmHg。当Ahmed和Krupin瓣膜浸入时，无法确定开启或关闭压力。在体外，在平衡盐溶液流速为2微升/分钟时，Ahmed和OptiMed装置的压力高于其他装置。在用血浆灌注期间，只有OptiMed装置保持比平衡盐更高的压力。对于所有装置，流动停止后压力迅速降至零。OptiMed装置显示出最高的阻力值。在体内，在流速为2微升/分钟时，Ahmed装置的压力为7.5±0.8 mmHg，OptiMed装置的压力为19.6±5.6 mmHg。流动停止15分钟后，OptiMed植入物的压力保持在7.1±1.1 mmHg。Baerveldt（未结扎）、Krupin和Molteno双腔植入物在体内具有相似的阻力和压力。结膜伤口破裂后，所有装置在体内的压力迅速降至零。
当在体外浸入平衡盐溶液或血浆中测试时，Ahmed和Krupin装置均未显示出可证明的开启或关闭压力。对于所有装置，由于外植体周围的组织诱导阻力，体内压力高于体外。在研究的流速下，Ahmed和Krupin瓣膜均起到限流装置的作用，但在初始液体灌注后并未关闭。
