Relationships among systemic blood pressure, intraocular pressure, and open-angle glaucoma

Several vascular factors, including systemic hypertension (or high blood pressure [HBP]), ocular perfusion pressure, and nocturnal hypotension, have been identified as risk factors for the development and progression of glaucoma. The results of epidemiologic studies of these factors and their relationships to intraocular pressure (IOP) and open-angle glaucoma (OAG) have been contradictory. Inconsistent definitions of HBP and OAG, inconsistent design, and differing population characteristics within these studies have obfuscated definitive conclusions. Here, we review the relationships among blood pressure, IOP, and OAG.     

The role of blood pressure in glaucoma

Although intraocular pressure (IOP) remains an important risk factor for glaucoma, it is clear that other factors can also influence disease development and progression. More recently, the role that blood pressure (BP) has in the genesis of glaucoma has attracted attention, as it represents a clinically modifiable risk factor and thus provides the potential for new treatment strategies beyond IOP reduction. The interplay between blood pressure and IOP determines the ocular perfusion pressure (OPP), which regulates blood flow to the optic nerve. If OPP is a more important determinant of ganglion cell injury than IOP, then hypotension should exacerbate the detrimental effects of IOP elevation, whereas hypertension should provide protection against IOP elevation. Epidemiological evidence provides some conflicting outcomes of the role of systemic hypertension in the development and progression of glaucoma. The most recent study showed that patients at both extremes of the blood pressure spectrum show an increased prevalence of glaucoma. Those with low blood pressure would have low OPP and thus reduced blood flow; however, that people with hypertension also show increased risk is more difficult to reconcile. This finding may reflect an inherent blood flow dysregulation secondary to chronic hypertension that would render retinal blood flow less able to resist changes in ocular perfusion pressure. Here we review both clinical and experimental studies that have attempted to clarify the relationships among blood pressure, OPP and blood flow autoregulation in the pathogenesis of glaucoma.     

婴幼儿眼压及其影响因素

婴幼儿的眼球处于生长发育中,角膜厚度和巩膜硬度均与成年人有所不同,在临床工作中,不应以成年人的正常眼压值范围来评估婴幼儿眼压.婴幼儿在测量中不能配合,多需镇静催眠,测量状态与成年人完全不同,婴幼儿在镇静状态下和在清醒状态下测量得到眼压值有显著差异.同时,眼压计选择的不同、中央角膜厚度、年龄等因素均可影响眼压值测量结果.因而,选择一种适合婴幼儿的眼压计,考虑相关因素对眼压值的影响,得到婴幼儿的正常眼压值对临床疾病的评估非常重要.     

中国陕西省农村人群血压、眼压和原发性开角型青光眼流行病学调查

目的：调查中国陕西省农村≥50岁人群原发性开角型青光眼、眼内压与全身血压的联系。 方法：2003-07／12，采用整体随机分层抽样法在陕西省洋县、靖边县及富平县调查8500人，其中≥50岁人群2125人，所有受检人员均进行标准问卷调查及详细的眼科检查，包括视力检查、裂隙灯检查、测量眼压及散瞳后直接检眼镜检查眼底。受检者于坐位测量血压。若有可疑青光眼性视盘损害或眼压高于22mmHg者则应进行视野检查。 结果：≥50岁人群中有1775人完成了青光眼的相关检查，受检率为83．53％。通过相关分析，发现此人群中眼压与全身性血压有显著相关性；眼压与收缩压均随年龄的增长而显著升高。通过多因素logistic回归分析，显示原发性开角型青光眼与低舒张期灌注压有显著联系，但未发现原发性开角型青光眼与高血压的显著联系。 结论：中国陕西省农村≥50岁人群中原发性开角型青光眼的患病率与中国其他报道相近。证实较低的舒张期灌注压是原发性开角型青光眼的一个重要危险因素。     

The relation between intraocular pressure change and plasma natriuretic peptide under simulated hypobaric conditions

Purpose:

To ascertain whether the changes in intraocular pressure (IOP) that occur during hypobaric hypoxic exposure are related to plasma N-terminal pro-brain natriuretic peptide (BNP) levels.

Materials and Methods:

The study group comprised 26 healthy participants (all male, mean age 23.1 years). IOP was measured at local ground level, (792 m above sea level), then while in a chamber providing hypobaric hypoxic conditions (the subjects were exposed to a pressure equivalent to 9144 m for 1-3 min), and again after exit from the chamber. In each condition, the mean of three consecutive measurements of IOP was calculated for each eye. For BNP measurements, blood samples were drawn before the participants entered the chamber and just after they left the chamber.

Results:

IOP during hypobaric hypoxic exposure (18.00 ± 3.70 mmHg) was significantly greater than that before (15.66 ± 2.10 mmHg, P < 0.001) or after (16.10 ± 2.63 mmHg, P = 0.001) the exposure. IOP levels before and after the exposure were not significantly different (P = 0.136). Plasma BNP levels measured before and after exposure to hypobaric hypoxic conditions were not significantly different (P = 0.462).

Conclusion:

Plasma BNP levels did not change after short-term hypobaric hypoxic exposure, while the IOP increased. This increase may have been caused by some other systemic factors. As the hypobaric hypoxic conditions were reversed, IOP decreased to normal levels.     

Factors affecting ocular pulse amplitude in eyes with open angle glaucoma and glaucoma‐suspect eyes

Purpose: To investigate the associations between ocular pulse amplitude (OPA) as measured by dynamic contour tonometry (DCT) and ocular and systemic factors in patients with open angle glaucoma (OAG) and in glaucoma suspects. Methods: One hundred and seventy‐three glaucoma‐suspect patients were consecutively enrolled. All subjects underwent intraocular pressure (IOP) measurement by DCT and Goldmann applanation tonometry (GAT), OPA measurement by DCT, Humphrey visual field (HVF) examination and central corneal thickness measurements. Arterial pulse amplitude (APA) and ocular perfusion pressure (OPP) were defined as the difference between systolic and diastolic BP and the difference between mean arterial pressure and IOP, respectively. All subjects also completed a systemized questionnaire on systemic vascular morbidities. Results: Seventy‐four eyes were diagnosed with OAG, based on HVF results. The overall mean CCT was 538.2 ± 37.6 μm. In all 173 eyes, OPA was associated with spherical equivalent (SE, p < 0.001) and with IOP by GAT (p = 0.013) by multivariate analysis. Multivariate analysis of the 77 subgroup eyes of patients for whom BP parameters were available also revealed that OPA was associated with SE (p = 0.007) and with IOP by GAT (p < 0.001). When the subjects were classified into the groups with low, intermediate and high cardiovascular risk based on the questionnaire, there was no difference in OPA among these groups (p > 0.05). Conclusions: Ocular pulse amplitude was associated with IOP measured by GAT and SE in patients with OAG and in glaucoma suspects. There was neither significant correlation between systemic hemodynamic parameters and OPA, nor difference of OPA in patients with different cardiovascular risk. OPA is primarily a measure of pressure, and there are certain limitations towards its use as a hemodynamic index.     

青光眼昼夜眼压波动

病理性高眼压和较大的昼夜眼压波动是青光眼视神经损害进展的重要危险因素.眼压具有波动性,正常人眼压波动的峰值多出现于凌晨,这种波动与体位、眼灌注压、眼轴等有关.正常眼压性青光眼患者眼压波动是视野进展的重要危险因素,且经24小时眼压监测发现大部分眼压是存在异常的,因此需根据其昼夜眼压曲线明确诊断和针对性治疗;原发性开角型青光眼患者昼夜眼压波动规律与正常人相似,眼压高峰多在夜间,但波动范围可能比正常人大,且双眼的波动呈明显的一致性;激光周边虹膜切开术后的慢性闭角型青光眼患者的昼夜眼压波动较大,其眼压波动与基线眼压和房角粘连程度呈正相关.与激光和药物相比,小梁切除术更有利于控制长期和昼夜的眼压波动.抗青光眼药物中前列腺素类药物是控制昼夜眼压波动效果最好的滴眼剂.     

原发性开角型青光眼进展的危险因素研究概况

原发性开角型青光眼(POAG)进展的危险因素包括全身性及眼部因素,眼部因素包括眼压及非眼压因素.在以往的多中心研究中,眼压对于由高眼压症发展为POAG及其在POAG进展中的作用已经明确,而目前降低眼压也是临床惟一有效地延缓、控制青光眼视神经损害进展的主要因素.制定目标眼压,进行降眼压治疗尤其是控制昼夜眼压波动对于阻止青光眼进展非常重要.非眼压危险因素包括高龄、中央角膜厚度增厚、视乳头出血、晶状体囊膜剥脱征、初始的青光眼严重程度及双眼罹患青光眼等.其他因素包括近视、青光眼家族史、眼部低灌注压、低血压、心血管疾病、高血压、高血脂等血管或血液性因素.POAG进展的危险因素研究在一定程度上揭示了POAG的发病机制及临床发病规律,对于指导临床医师决定随诊频率、选择治疗方案及提高治疗效率意义重大.     

Association between ocular pressure and certain health parameters

Intraocular pressure (IOP) was measured in a mixed population of 12,803 apparently healthy employed people. Mean IOP was 13.5 +/- 3.3 mmHg, without sex difference. Frequency distribution demonstrated skewness towards high values. IOP weakly correlated with age (R = 0.06), and older subgroups showed more marked skewness, but further analysis showed this effect to be spurious. The correlations of IOP with heart rate and with systolic blood pressure were small, but stronger than with age (R = .16 and .15, respectively). Moreover, when corrected for heart rate, the effect of age was nullified. Other factors found to be correlated with IOP included blood glucose and hemoglobin concentration, smoking, and height. None of these factors significantly increased the correlation between IOP and heart rate or blood pressure, and the skewness was not fully explained by any of these factors or their combinations. The value of the epidemiologic approach to detection of factors responsible for ocular hypertension is stressed.     

辯證地認識眼壓在青光眼診斷中的地位

青光眼是不可复性且盲的主要病因之一,防盲的关键在于早期诊断早期治疗 眼压是表演光眼诊断的一个重要指标 眼压测量值的统计学正常值范围与每一个体生理学上要求的正常眼压(健常眼压)是不同的概念 本文对影响眼压水平的因素、对眼压正常值的统计学认识及影响不同个体的健常眼压水平的因素问题进行了讨论,提出要辩证地认识眼压在青光眼诊断中的地位。认为眼压是诊断青光眼不可缺少的指标之一,但不能将某一特定的眼压值作为青光眼与正常人的分水兹