Vision Science Graduate Program, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States.
Department of Ophthalmology and Visual Sciences, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.
Invest Ophthalmol Vis Sci. 2020 Oct 1;61(12):18. doi: 10.1167/iovs.61.12.18.
Recent retrospective clinical studies and animal experiments have suggested that cerebrospinal fluid pressure (CSFP) is important in glaucoma, acting through the translaminar pressure (TLP = IOP - CSFP), which directly affects the optic nerve head. In this study, IOP and intracranial pressure (ICP; a surrogate of CSFP) were measured at various body positions to quantify the determinants of TLP.
We have developed an implantable wireless pressure telemetry system based on a small piezoelectric sensor with low temporal drift. Telemetry transducers were placed in the anterior chamber to measure IOP and in the brain parenchyma at eye height to measure ICP. IOP was calibrated against anterior cannulation manometry, and ICP/CSFP was calibrated against an intraparenchymal Codman ICP Express microsensor. We measured IOP, ICP, and TLP = IOP - ICP continuously at 200 Hz in three male nonhuman primates (NHPs) in three trials; pressures were then averaged for 30 seconds per body position. Relative change of IOP, ICP, and TLP from the supine (baseline) position to the seated, standing, and inverted positions were quantified.
TLP changed significantly and instantaneously from the supine to seated (+14 mm Hg), supine to standing (+13 mm Hg) and supine to inverted (-12 mm Hg) positions (P < 0.05). There was no significant TLP change for supine to prone. ICP showed greater relative change than IOP.
TLP change due to body position change is driven more by ICP/CSFP than IOP. IOP, ICP, and TLP variability, coupled with telemetry, should allow us to test the hypotheses that IOP, ICP, or TLP fluctuations contribute independently to glaucoma onset or progression.
最近的回顾性临床研究和动物实验表明，脑脊液压力（CSFP）在青光眼中有重要作用，通过跨层压（TLP=IOP-CSFP）起作用，该压力直接影响视神经头。在这项研究中，我们在不同体位下测量了眼压（IOP）和颅内压（CSFP 的替代指标；ICP），以量化 TLP 的决定因素。
我们开发了一种基于具有低时间漂移的小型压电传感器的可植入无线压力遥测系统。遥测传感器被放置在前房以测量 IOP，并放置在眼高的脑实质中以测量 ICP。IOP 通过前房插管测压法进行校准，ICP/CSFP 通过颅内 Codman ICP Express 微传感器进行校准。我们在 3 只雄性非人类灵长类动物（NHPs）中进行了 3 次试验，以 200Hz 的频率连续测量 IOP、ICP 和 TLP=IOP-ICP，然后对每个体位的 30 秒数据进行平均。量化了从仰卧位（基线）到坐位、站立位和倒置位时 IOP、ICP 和 TLP 的相对变化。
TLP 从仰卧位到坐位（+14mmHg）、仰卧位到站立位（+13mmHg）和仰卧位到倒置位（-12mmHg）时发生显著且瞬时的变化（P<0.05）。从仰卧位到俯卧位时 TLP 没有明显变化。ICP 的相对变化大于 IOP。
体位变化引起的 TLP 变化主要由 ICP/CSFP 驱动，而不是 IOP。IOP、ICP 和 TLP 的变异性，加上遥测技术，应该使我们能够测试眼压、颅内压或 TLP 波动是否独立导致青光眼发作或进展的假说。
