Department of Clinical Pharmacology, Medical University of Vienna, Austria.
Exp Eye Res. 2011 Aug;93(2):141-55. doi: 10.1016/j.exer.2010.09.002. Epub 2010 Sep 22.
Glaucoma is an optic neuropathy of unknown origin. The most important risk factor for the disease is an increased intraocular pressure (IOP). Reducing IOP is associated with reduced progression in glaucoma. Several recent large scale trials have indicated that low ocular perfusion pressure (OPP) is a risk factor for the incidence, prevalence and progression of the disease. This is a strong indicator that vascular factors are involved in the pathogenesis of the disease, a hypothesis that was formulated 150 years ago. The relation between OPP and blood flow to the posterior pole of the eye is, however, complex, because of a phenomenon called autoregulation. Autoregulatory processes attempt to keep blood flow constant despite changes in OPP. Although autoregulation has been observed in many experiments in the ocular vasculature the mechanisms underlying the vasodilator and vasoconstrictor responses in face of changes in OPP remain largely unknown. There is, however, recent evidence that the human choroid regulates its blood flow better during changes in blood pressure induced by isometric exercise than during changes in IOP induced by a suction cup. This may have consequences for our understanding of glaucoma, because it indicates that blood flow regulation is strongly dependent not only on OPP, but also on the level of IOP itself. Indeed there is data indicating that reduction of IOP by pharmacological intervention improves optic nerve head blood flow regulation independently of an ocular vasodilator effect.
青光眼是一种病因不明的视神经病变。该病最重要的危险因素是眼内压（IOP）升高。降低 IOP 与青光眼的进展减少有关。最近的几项大规模试验表明，低眼灌注压（OPP）是疾病发生、流行和进展的危险因素。这强烈表明血管因素参与了疾病的发病机制，这一假说早在 150 年前就已提出。然而，由于存在一种称为自动调节的现象，OPP 与眼球后极血流之间的关系非常复杂。自动调节过程试图在 OPP 变化时保持血流量恒定。尽管在许多眼血管实验中观察到了自动调节，但在面对 OPP 的变化时，血管舒张和收缩反应的机制在很大程度上仍然未知。然而，最近有证据表明，在由等长运动引起的血压变化期间，人类脉络膜比在由吸盘引起的 IOP 变化期间更好地调节其血流。这可能会对我们对青光眼的理解产生影响，因为这表明血流调节不仅取决于 OPP，还取决于 IOP 本身的水平。事实上，有数据表明，通过药物干预降低 IOP 可改善视神经头血流调节，而与眼部血管扩张作用无关。
