Cunha-Vaz J G
Doc Ophthalmol. 1976 Oct 15;41(2):287-327. doi: 10.1007/BF00146764.
The Blood-Retinal Barrier (BRB) is a situation of restricted permeability which is present between the blood and the retina. This barrier has a well defined anatomic substrate, particular permeability characteristics and appears to play a role of major importance in the pathophysiology and therapeutics of retinal disease. The BRB phenomenon operates fundamentally at two levels, retinal vessels and chorioepithelial interface, forming which may be better called an inner BRB and an outer BRB. The main structures involved are, for the inner BRB, the endothelial membrane of the retinal vessels, and for the outer BRB, the retinal pigment epithelium. 'Zonulae occludentes' are present in these membranes forming complete belts around the cells, sealing off the spaces between them. Other structures appear to play an accessory role. Both barriers show an apparent predominance of processes of active transport over mechanisms of passive transfer, these being extremely restricted. Much information on the pathophysiology of the BRB mechanism has been obtained from studies of its experimental breakdown. In this way, a breakdown of the inner BRB may be induced by acute distension of the vessel walls, ischaemia, chemical influences, defects in the endothelial cells and failure of the active transport system, whereas experimental ischaemia, mechanical distension of the pigment epithelial membrane, defects in the pigment epithelium and failure of the active transport systems can cause a breakdown of the outer BRB. The increased permeability of the inner BRB, and of the outer BRB, appears to be related to changes in the vascular endothelial membrane and retinal pigment epithelium, respectively. In clinical ophthalmology there are two methods for the diagnosis of breakdown of the BRB, fundus fluorescein angiography and vitreous fluorophotometry. Vitreous fluorophotometry being capable of detecting functional alterations of the barrier before any pathological changes are apparent. There is evidence of an intimate relationship between breakdown of the BRB and almost every retinal disease, particularly the vascular retinopathies and the pigment epitheliopathies. Diabetic retinopathy, hypertensive retinopathy, retinal vein obstruction, blood diseases, trauma or surgery to the eye, temporary arterial obstruction, perivasculitis, Behçet's and Coats' diseases, retinoblastoma, hemangioblastoma and retinal neovascularization are examples of situations where a breakdown of the inner BRB has been demonstrated. On the other hand, examples of breakdown of the outer BRB include situations of choroidal ischaemia, detachment of the pigment epithelium, choroidal neovascularization, photocoagulation, retinal detachment, Koyanagi's disease, central serous choroidopathy, multifocal inner choroiditis and acute placoid pigment epitheliopathy.
血视网膜屏障（BRB）是血液与视网膜之间存在的一种通透性受限的状态。该屏障具有明确的解剖学基础、特定的通透性特征，并且在视网膜疾病的病理生理学和治疗中似乎起着至关重要的作用。BRB现象主要在两个层面发挥作用，即视网膜血管和脉络膜上皮界面，由此形成的可更好地称为内BRB和外BRB。涉及的主要结构，对于内BRB来说，是视网膜血管的内皮膜，对于外BRB来说，是视网膜色素上皮。“紧密连接”存在于这些膜中，围绕细胞形成完整的带，封闭它们之间的间隙。其他结构似乎起辅助作用。两个屏障都显示出主动转运过程明显优于被动转运机制，被动转运机制极为有限。关于BRB机制病理生理学的许多信息是通过对其实验性破坏的研究获得的。通过这种方式，内BRB的破坏可由血管壁急性扩张、缺血、化学影响、内皮细胞缺陷和主动转运系统功能障碍引起，而实验性缺血、色素上皮膜机械扩张、色素上皮缺陷和主动转运系统功能障碍可导致外BRB的破坏。内BRB和外BRB通透性增加似乎分别与血管内皮膜和视网膜色素上皮的变化有关。在临床眼科中，有两种诊断BRB破坏的方法，即眼底荧光血管造影和玻璃体荧光光度测定法。玻璃体荧光光度测定法能够在任何病理变化明显之前检测到屏障的功能改变。有证据表明BRB破坏与几乎每种视网膜疾病都密切相关，特别是血管性视网膜病变和色素上皮病变。糖尿病性视网膜病变、高血压性视网膜病变、视网膜静脉阻塞、血液疾病、眼外伤或手术、暂时性动脉阻塞、血管周围炎、白塞病和科茨病、视网膜母细胞瘤、成血管细胞瘤和视网膜新生血管形成都是已证明内BRB破坏的例子。另一方面，外BRB破坏的例子包括脉络膜缺血、色素上皮脱离、脉络膜新生血管形成、光凝、视网膜脱离、小柳原田病、中心性浆液性脉络膜病变、多灶性内层脉络膜炎和急性扁平状色素上皮病变。
