Department of Ophthalmology, Second Affiliated Hospital of Harbin Medical University, Harbin, China.
Ophthalmic Res. 2011;45(3):113-21. doi: 10.1159/000317034. Epub 2010 Sep 17.
To evaluate the threshold currents required by different-size electrodes under various stimulus parameters by suprachoroidal-transretinal stimulation (STS) in rabbit eyes.
An electrode array with 4 differently sized electrode contacts (50, 150, 350 and 500 μm in diameter) was implanted into the suprachoroidal space of the rabbit eyes. The electrically evoked potential was recorded extradurally on the visual cortex, and the threshold was measured for each size electrode by a biphasic current pulse at the pulse durations of 0.25, 0.5, 0.75 and 1.0 ms. Stimuli were applied at 1, 2 and 4 Hz.
The current thresholds with the 50-μm electrode were 80 ± 21.2 and 41.4 ± 6.5 μA for 0.25- and 1.0-ms pulses, respectively. That obviously exceeded the limits for safe stimulation with platinum. Compared to 350- and 500-μm electrodes, a lower threshold can be obtained by the 150-μm electrode just at 1 Hz. And the most significant change in the threshold as the stimulus frequency increased to 4 Hz was obtained by the 150-μm electrode with short-duration pulse (0.25 ms).
The large surface electrode with long-duration pulses may be preferable for the STS prosthesis. And stimuli with low frequency are suggested to be the safer choice.
通过兔眼脉络膜上腔-视网膜下刺激（STS）评估不同大小电极在各种刺激参数下所需的阈值电流。
将一个带有 4 个不同大小电极触点（直径分别为 50、150、350 和 500μm）的电极阵列植入兔眼脉络膜上腔。在硬脑膜外记录电诱发电位，并用双相电流脉冲测量每个尺寸电极的阈值，脉冲持续时间为 0.25、0.5、0.75 和 1.0ms。刺激频率为 1、2 和 4Hz。
50μm 电极的电流阈值分别为 80±21.2μA 和 41.4±6.5μA，分别用于 0.25ms 和 1.0ms 脉冲。这明显超过了铂安全刺激的限制。与 350μm 和 500μm 电极相比，150μm 电极在 1Hz 时可以获得更低的阈值。并且，在刺激频率增加到 4Hz 时，150μm 电极的短脉冲（0.25ms）获得了阈值的最大变化。
对于 STS 假体，大表面积的长脉冲电极可能更可取。建议选择低频刺激，以确保更安全。
