Lozano Diana C, Hartwick Andrew T E, Twa Michael D
College of Optometry, University of Houston , Houston, TX , USA and.
Chronobiol Int. 2015 May;32(4):513-23. doi: 10.3109/07420528.2015.1008135. Epub 2015 Mar 23.
Ocular hypertension is a risk factor for developing glaucoma, which consists of a group of optic neuropathies characterized by progressive degeneration of retinal ganglion cells and subsequent irreversible vision loss. Our understanding of how intraocular pressure damages the optic nerve is based on clinical measures of intraocular pressure that only gives a partial view of the dynamic pressure load inside the eye. Intraocular pressure varies over the course of the day and the oscillator regulating these daily changes has not yet been conclusively identified. The purpose of this study was to compare and contrast the circadian rhythms of intraocular pressure and body temperature in Brown Norway rats when these animals are housed in standard light-dark and continuous dim light (40-90 lux) conditions. The results from this study show that the temperature rhythm measured in continuous dim light drifted forward relative to external time, indicating that the rhythm was free running and being regulated by an internal biological clock. Also, the results show that there is a persistent, but dampened, circadian rhythm of intraocular pressure in continuous dim light and that the circadian rhythms of temperature and intraocular pressure are not synchronized by the same central oscillator. We conclude that once- or twice-daily clinical measures of intraocular pressure are insufficient to describe intraocular pressure dynamics. Similarly, our results indicate that, in experimental animal models of glaucoma, the common practice of housing animals in constant light does not necessarily eliminate the potential influence of intraocular pressure rhythms on the progression of nerve damage. Future studies should aim to determine whether an oscillator within the eye regulates the rhythm of intraocular pressure and to better characterize the impact of glaucoma on this rhythm.
高眼压是青光眼发病的一个危险因素，青光眼是一组以视网膜神经节细胞进行性退变及随后不可逆视力丧失为特征的视神经病变。我们对眼内压如何损害视神经的理解基于眼内压的临床测量，而这种测量仅能部分反映眼内动态压力负荷情况。眼内压在一天中会发生变化，且调节这些每日变化的振荡器尚未得到最终确认。本研究的目的是比较和对比棕色挪威大鼠在标准明暗循环和持续暗光（40 - 90勒克斯）条件下眼内压和体温的昼夜节律。本研究结果表明，在持续暗光条件下测量的温度节律相对于外部时间向前漂移，这表明该节律是自由运行的，且受内部生物钟调节。此外，结果还表明，在持续暗光条件下存在持续但减弱的眼内压昼夜节律，并且温度和眼内压的昼夜节律并非由同一个中枢振荡器同步。我们得出结论，每天一次或两次的眼内压临床测量不足以描述眼内压动态变化。同样，我们的结果表明，在青光眼实验动物模型中，将动物饲养在持续光照环境中的常见做法不一定能消除眼内压节律对神经损伤进展的潜在影响。未来的研究应旨在确定眼内是否存在一个振荡器调节眼内压节律，并更好地描述青光眼对该节律的影响。
