Quick Facts
The outer five layers of the retina receives its blood supply from vessels in the choroid. The inner layers of the retina receive blood from the ophthalmic artery via the central retinal artery.
Structure and/or Key Features
The retina requires a blood supply from two sources in order to maintain proper function. The outer five layers of the retina are supported metabolically by diffusion from the vasculature of the choroid (choriocapillaris). The inner layers of the retina receive blood from capillaries that arise from the central retinal artery, a branch of the ophthalmic artery. The central retinal artery passes within the optic nerve to enter the eye through the lamina cribrosa. It then divides into superior and inferior branches, which in turn give rise to superior and inferior nasal and superior and inferior temporal branches. Each of these branches supplies a quadrant of the retina. They do not overlap or anastomose with each other, thus, if an artery becomes blocked, loss of vision occurs in the corresponding quadrant. These vessels run within the layer of nerve fibers and the ganglion cell layer of the retina and are easily visualized through an ophthalmoscope. Arterioles arising from these arteries pass deeply, into the layers of the retina to form capillary networks. These capillary beds can be found in three layers:
- radial peripapillary capillaries, within the layer of nerve fibers;
- inner capillaries, within the inner aspect of the layer of nerve fibers and ganglionic layer;
- outer capillaries, in the inner plexiform and inner nuclear layers (Standring, 2016).
On approaching the fovea, capillaries terminate by joining a single-layered macular capillary ring that results in a capillary free region around the fovea. Additionally, capillaries are absent as the retina thins peripherally near the ora serrata.
Retinal blood vessels share much of the same morphology as those in other parts of the body; however, they lack an internal elastic lamina in the arterial wall, and smooth muscle may be found in the tunica adventitia. Capillaries are not fenestrated in order to maintain a “blood-retina barrier.” Instead, the endothelium contains tight junctions to maintain a tight seal (Standring, 2016).
References
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.
