Dynamic impedance measurements during radio-frequency heating of cornea
Dynamic impedance measurements during radio-frequency heating of cornea
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DOI：
10.1109/tbme.2002.805471
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发表时间：
2002-12-01
影响因子：
4.6
通讯作者：
Pearce, JA
中科院分区：
文献类型：
--
作者：
Choi, B;Kim, JH;Pearce, JA
远视影响大约25%的人口。用于治疗远视的不同加热模式的目的是使角膜的中心曲率变陡。传导性角膜移植术（CK）涉及在与眼睛瞳孔同心的直径为7 mm的环周围放置射频（RF）损伤。CK过程中损伤形成的动力学依赖于角膜电阻抗，这是预期在每个600 ms长的macropulse. This研究的目的是测量阻抗动态CK过程中发生变化。在不同的功率设置下，在离体猪眼中进行射频损伤。电压和电流的测量是使用基于高速计算机的数据采集系统获得的。计算每个微脉冲的均方根电压（V-RMS）和电流（I-RMS），并通过计算商V-RMS/I-RMS确定阻抗。体外初始角膜阻抗约为2000 Ω。在宏脉冲期间，由于导电离子的迁移率增加，阻抗最初降低。在较高的功率设置（例如，> 70%，或最大峰间电压为233 V），阻抗在初始降低后增加，表明局部水汽化和/或组织凝固。在体内猪眼获得的初步阻抗数据的大小与体外值相似。
Hyperopia affects approximately 25% of the population. The aim of different heating modalities for the treatment of hyperopia is to steepen the central curvature of the cornea. Conductive keratoplasty (CK) involves the placement of radio-frequency (RF) lesions around a 7-mm-diameter ring concentric with the pupil of the eye. Dynamics of lesion formation during CK depend on corneal electrical impedance, which is expected to change during each 600-ms-long macropulse.The purpose of this study was to measure impedance dynamics during CK. RF lesions were made in in vitro porcine eyes at different power settings. Voltage and current measurements were acquired using-a high-speed computer-based data acquisition system. Root-mean-square voltages (V-RMS) and currents (I-RMS) were calculated for each micropulse, and impedance was determined by calculating the quotient V-RMS/I-RMS. Initial corneal impedance in vitro was approximately 2000 Omega. During the macropulse, impedance decreased initially due to increased mobility of conductive ions. At higher power settings (e.g., > 70 %, or maximum peak-to-peak voltage of 233 V), impedance increased after the initial decrease, indicative of local water vaporization and/or tissue coagulation. Preliminary impedance data obtained for in vivo porcine eyes were similar in magnitude to the in vitro values.