The Blood Ocular Barrier: An Anatomical Review
The blood ocular barriers serve critical functions in maintaining physiological conditions in the human eye. The blood ocular barrier is primarily divided into two components, the blood aqueous barrier and the blood retinal barrier, itself divisible into the inner and outer blood retinal barrier. The existences of such barriers were postulated following the discovery of the blood brain barrier in the late 19th century. Understanding of the blood barrier was in part due to experiments in which trypan blue was injected intravenously into the circulation of animals resulting in bright blue staining of the tissues of the animal’s body globally with the exception of the brain and spinal cord, which was described as snow white. Further derivatives of these experiments lead to the discovery of the blood aqueous barrier. The blood retinal barrier was subsequently discovered by studying the effect of histamine on blood vessels around the body. Peripherally histamine increases permeability of blood vessels however cerebral and retinal vessels are unique in this way, as histamine has no effect on their permeability.
