Blood–retinal barrier

The blood–retinal barrier, or the BRB, is part of the blood–ocular barrier that consists of cells that are joined tightly together to prevent certain substances from entering the tissue of the retina.[1] It consists of non-fenestrated capillaries of the retinal circulation and tight-junctions between retinal epithelial cells preventing passage of large molecules from choriocapillaris into the retina.

Structure

The blood retinal barrier has two components: the retinal vascular endothelium and the retinal pigment epithelium.[2] Retinal blood vessels that are similar to cerebral blood vessels maintain the inner blood-ocular barrier. This physiological barrier comprises a single layer of non-fenestrated endothelial cells, which have tight junctions. These junctions are impervious to tracer, so many substances can affect the metabolism of the eyeball. The retinal pigment epithelium maintains the outer blood–retinal barrier.[3]

Clinical significance

Diabetic retinopathy

Diabetic retinopathy, eye damage that frequently occurs as a result of diabetes, is related to the breakdown of the blood–retinal barrier.[4] The barrier becomes more leaky in patients with diabetic retinopathy.[5]

Other animals

Animal models have shown that the blood–retinal barrier becomes more permeable to substances in hypertensive animals (those with high blood pressure).[6]

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See also
  • Blood–air barrier – Membrane separating alveolar air from blood in lung capillaries
  • Blood–brain barrier – Semipermeable capillary border that allows selective passage of blood constituents into the brain
  • Blood–ocular barrier – A physical barrier between the local blood vessels and most parts of the eye itself
  • Blood–testis barrier – A physical barrier between the blood vessels and the seminiferous tubules of the animal testes
  • Blood–thymus barrier – A barrier formed by the continuous blood capillaries in the thymic cortex

References
  1. Biologyonline.org. Blood–retinal barrier. Retrieved on July 19, 2007.
  2. Vinores, SA (1995). "Assessment of blood–retinal barrier integrity". Histology and Histopathology. 10 (1): 141–54. PMID 7756735.
  3. Pardianto, G; et al. (2005). "Blood–retinal-barrier". Mimbar Ilmiah Oftalmologi Indonesia. 2: 68–69.
  4. Azza B. El-Remessy, Mohamed Al-Shabrawey, Yousuf Khalifa, Nai-Tse Tsai, Ruth B. Caldwell and Gregory I. Liou. 2006. Neuroprotective and Blood–retinal Barrier-Preserving Effects of Cannabidiol in Experimental Diabetes. American Journal of Pathology, Volume 168, Pages 235-244. Retrieved on July 19, 2007.
  5. Lobo, CL; Bernardes, RC; Cunha-Vaz, JG. (2000). "Alterations of the Blood–retinal Barrier and Retinal Thickness in Preclinical Retinopathy in Subjects With Type 2 Diabetes". Archives of Ophthalmology. 118 (10): 1364–1369. doi:10.1001/archopht.118.10.1364. PMID 11030818.
  6. S Lightman, E Rechthand, C Latker, A Palestine and S Rapoport. Assessment of the permeability of the blood–retinal barrier in hypertensive rats. Hypertension, Volume 10, Pages 390-395. Retrieved on July 19, 2007.
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