Medical Engineering Department, University of South Florida, Tampa, FL, 33620, USA.
Medical Engineering Department, University of South Florida, Tampa, FL, 33620, USA; Ophthalmology Department, University of South Florida, Tampa, FL, 33620, USA.
Exp Eye Res. 2021 Sep;210:108727. doi: 10.1016/j.exer.2021.108727. Epub 2021 Aug 12.
Intraocular pressure (IOP) is important for eye health as abnormal levels can led to ocular tissue damage. IOP is typically estimated by tonometry, which only provides snapshots of pressure history. Tonometry also requires subject cooperation and corneal contact that may influence IOP readings. The aim of this research was to investigate IOP dynamics of conscious animals in response to stressors, common anesthetics, tonometry, and temperature manipulations. An eye of male Brown-Norway rats was implanted with a fluid-filled cannula connected to a wireless telemetry system that records IOP continuously. Stress effects were examined by restricting animal movements. Anesthetic effects were examined by varying isoflurane concentration or injecting a bolus of ketamine. Tonometry effects were examined using applanation and rebound tonometers. Temperature effects were examined by exposing anesthetized and conscious animals to warm or cool surfaces. Telemetry recordings revealed that IOP fluctuates spontaneously by several mmHg, even in idle and anesthetized animals. Environmental disturbances also caused transient IOP fluctuations that were synchronous in recorded animals and could last over a half hour. Animal immobilization produced a rapid sustained elevation of IOP that was blocked by anesthetics, whereas little-to-no IOP change was detected in isoflurane- or ketamine-anesthetized animals if body temperature (BT) was maintained. IOP and BT decreased precipitously when heat support was not provided and were highly correlated during surface temperature manipulations. Surface temperature had no impact on IOP of conscious animals. IOP increased slightly during applanation tonometry but not rebound tonometry. The results show that IOP is dynamically modulated by internal and external factors that can activate rapidly and last long beyond the initiating event. Wireless telemetry indicates that animal interaction induces startle and stress responses that raise IOP. Anesthesia blocks these responses, which allows for better tonometry estimates of resting IOP provided that BT is controlled.
眼压（IOP）对眼睛健康很重要，因为异常的眼压水平可能导致眼组织损伤。IOP 通常通过眼压计来估计，而眼压计只能提供压力历史的快照。眼压计还需要受试者的配合和角膜接触，这可能会影响眼压读数。本研究的目的是研究清醒动物对应激源、常见麻醉剂、眼压计和温度操作的 IOP 动态变化。雄性棕色挪威大鼠的一只眼睛植入了一个充满液体的套管，套管连接到一个无线遥测系统，该系统连续记录 IOP。通过限制动物的运动来检查应激效应。通过改变异氟烷浓度或注射氯胺酮来检查麻醉效果。通过使用压平眼压计和回弹眼压计来检查眼压计的效果。通过将麻醉和清醒动物暴露于温暖或凉爽的表面来检查温度的影响。遥测记录显示，即使在静止和麻醉状态下，IOP 也会自发波动数毫米汞柱。环境干扰也会引起短暂的 IOP 波动，这些波动在记录的动物中是同步的，可持续半小时以上。动物固定会导致 IOP 迅速持续升高，这种升高可被麻醉剂阻断，而在异氟烷或氯胺酮麻醉的动物中，如果体温（BT）得到维持，则几乎检测不到 IOP 变化。当不提供热支持时，IOP 和 BT 会急剧下降，并且在表面温度操作过程中高度相关。表面温度对清醒动物的 IOP 没有影响。在压平眼压计时，IOP 略有增加，但在回弹眼压计时则没有增加。结果表明，IOP 受到内部和外部因素的动态调节，这些因素可以迅速激活，并在启动事件后持续很长时间。无线遥测表明，动物相互作用会引起惊吓和应激反应，从而导致 IOP 升高。麻醉会阻断这些反应，从而允许更好地估计 BT 得到控制时的静息 IOP。
