Brubaker R F
Department of Ophthalmology, Mayo Clinic, Rochester, MN 55905.
Invest Ophthalmol Vis Sci. 1991 Dec;32(13):3145-66.
Based on clinical experiments with fluorophotometry, several observations can be made about aqueous flow through the chambers of the human eye. 1. The rate of flow is 2.75 +/- 0.63 microliters/min in normal subjects, as derived from measurements averaged during normal office hours. The normal range (95%) is 1.8 to 4.3 microliters/min. 2. There is a circadian rhythm of flow, with the highest rates during morning hours, slightly lower rates during afternoon hours, and rates during sleep that are approximately one half of those during the morning. The hormonal basis for this rhythm is unknown, but it is known to be present in both eyes of persons with unilateral Horner's syndrome. 3. A slight decline of the rate occurs after age 10 yr--3.2% per decade. There is no significant difference in aqueous flow between men and women. 4. Of the hundreds of drugs that are used clinically, most are unlikely to have a significant effect on aqueous flow. Exceptions are the beta-adrenergic agonists that, under certain circumstances, are able to increase flow, the corticosteroids that may have a stimulating effect on flow, and three classes of drugs that have therapeutically useful suppressing effects on flow: carbonic-anhydrase inhibitors, beta-adrenergic antagonists, and alpha 2-selective adrenergic agonists. 5. Timolol, which has a remarkably consistent suppressing effect on flow during the day, has no effect on the flow of sleeping subjects. By contrast, acetazolamide and apraclonidine are able to reduce the flow of sleeping subjects. 6. Acute doses of beta-adrenergic antagonists and alpha 2-agonists are not additive, but beta-adrenergic antagonists and carbonic-anhydrase inhibitors are partly additive. 7. The eye adapts partly to the chronic use of timolol and recovers from its effects when it is discontinued. 8. The rate of disappearance of the effect of beta-adrenergic antagonists is longer for the noncardioselective agents, such as timolol and levobunolol, but is relatively short for the cardioselective agent, betaxolol. 9. The rate of aqueous flow is insensitive to moderate changes of intraocular pressure. Clinical studies can provide suggestive leads for more basic investigations or test specific hypotheses. Biochemical, biologic, and pharmacologic approaches in simpler, more controlled experimental conditions are necessary to determine the fundamental processes that bring about aqueous formation in the living eye. The combination of many disciplines (eg, studying molecules, cells, tissues, organs, and the intact living system) has the best chance of furthering our understanding of the aqueous circulation.
基于荧光光度法的临床实验，可以对房水在人眼各腔室中的流动情况得出一些观察结果。1. 正常受试者的房水流动速率为2.75±0.63微升/分钟，这是根据正常办公时间内的测量平均值得出的。正常范围（95%）为1.8至4.3微升/分钟。2. 房水流动存在昼夜节律，上午时段流速最高，下午时段稍低，睡眠期间的流速约为上午的一半。这种节律的激素基础尚不清楚，但已知单侧霍纳综合征患者的双眼均存在这种节律。3. 10岁以后流速略有下降，每十年下降3.2%。男性和女性的房水流动没有显著差异。4. 在临床上使用的数百种药物中，大多数不太可能对房水流动产生显著影响。例外情况是β-肾上腺素能激动剂，在某些情况下能够增加房水流动；皮质类固醇可能对房水流动有刺激作用；还有三类药物对房水流动有治疗上有用的抑制作用：碳酸酐酶抑制剂、β-肾上腺素能拮抗剂和α2选择性肾上腺素能激动剂。5. 噻吗洛尔在白天对房水流动有显著一致的抑制作用，但对睡眠受试者的房水流动没有影响。相比之下，乙酰唑胺和阿可乐定能够降低睡眠受试者的房水流动。6. β-肾上腺素能拮抗剂和α2激动剂的急性剂量没有相加作用，但β-肾上腺素能拮抗剂和碳酸酐酶抑制剂有部分相加作用。7. 眼睛会部分适应噻吗洛尔的长期使用，停药后会从其作用中恢复。8. 非心脏选择性药物如噻吗洛尔和左布诺洛尔的β-肾上腺素能拮抗剂作用消失的速率较长，而心脏选择性药物倍他洛尔的作用消失速率相对较短。9. 房水流动速率对眼内压的适度变化不敏感。临床研究可为更基础的研究提供提示性线索或检验特定假设。在更简单、更可控的实验条件下采用生化、生物学和药理学方法，对于确定活体眼中房水形成的基本过程是必要的。多学科结合（例如研究分子、细胞、组织、器官和完整的活体系统）最有机会增进我们对房水循环的理解。
