The blood retinal barriers refer to a complex network of specialized structures and tight junctions that tightly regulate the movement of substances between the blood vessels and the retina, a delicate and vital tissue in the eye. These barriers serve the crucial function of maintaining the unique microenvironment necessary for the normal functioning of the retina.
There are two main blood retinal barriers: the inner blood retinal barrier (BRB) and the outer BRB. The inner BRB is formed by the tight junctions between the endothelial cells of the retinal capillaries, which prevent the passage of many substances from the blood into the retinal tissue. Additionally, the presence of pigment epithelial cells further reinforces the inner BRB by forming a continuous layer between the capillaries and the retina.
The outer BRB is composed of tight junctions between the cells of the retinal pigment epithelium (RPE), a layer of cells located between the photoreceptor cells of the retina and the underlying choroid. This barrier prevents the leakage of substances from the retina into the choroid, maintaining the integrity of the retinal tissue.
The blood retinal barriers play a crucial role in protecting the sensitive retinal tissue from the potential harmful effects of circulating substances, pathogens, and inflammatory molecules. They help regulate the exchange of nutrients, oxygen, and waste products, ensuring the appropriate supply of essential molecules to the retina while preventing toxic substances from entering.
Understanding the blood retinal barriers is essential for diagnosing and managing various retinal diseases, as their dysfunction or disruption can lead to pathological changes within the retina, such as macular degeneration, diabetic retinopathy, and retinal edema.
