Retinal capillaries

Roth spot Possible sign of endocarditis where there is localized capillary retinal bleeding. 

At about four months gestation, mesenchymal cells emanating from the central hyaloid vessel at the optic disc invade the inner layers of the retina. These endothelial complexes develop into capillaries as vascularization proceeds anteriorly in all directions towards the ora serrata from the optic nerve. As this progresses, so the embryonic hyaloid vessels in the vitreous undeigo regression. These retinal vessels do not, however, reach the most anterior portion of the retina until 8 months gestation and the anterior temporal retinal periphery, ferthest removed from the optic nerve, is not vascularized until about full term (Flower and Patz, 1971). 

Frank RN, Dutas S, Mancini MA. Pericyte coverage is greater in the retinal than in the cerebral capillaries of the rat. Invest Ophtalmol Visual Sci 1987 28 1089-1091. 

Figure 14.2 Phase contrast microscopic images of conditionally immortalized cells forming the inner blood-retinal barrier (A) and time-course of [3H] adenosine uptake by TR-iBRB cells (B). A Conditionally immortalized rat retinal capillary endothelial cell line TR-iBRB, retinal pericyte cell line TR-rPCT and Muller cell line TR-MUL. B The [ H]adenosine (14 nM) uptake was performed at 37°C in the presence (closed circle) or absence (open circle) of Na+.

Blood-to-retina influx transport GLUT1 D-Glucose/Dehydroascorbic acid + TR-iBRB Isolated retinal capillary [5, 13, 14, 43, 47]... 

PAH efflux transport p-Aminohippuric acid ND Isolated retinal capillary [13]... 

Immunohistochemical study ND not determined GLUT1 facilitative glucose transporter MCT1 monocarboxylate transporter CRT creatine transporter LAT1 L-type amino acid transporter TAUT taurine transporter ENT equilibrative nucleoside transporter Oatp organic anion-transporting polypeptide PAH p-aminohippuric acid RUI retinal uptake index TR-iBRB rat retinal capillary endothelial cells. 

K. Hosoya, M. Tomi, S. Ohtsuki, H. Takanaga, M. Ueda, N. Yanai, M. Obinata, and T. Terasaki. Conditionally immortalized retinal capillary endothelial cell lines (TR-iBRB) expressing differentiated endothelial cell functions derived from a transgenic rat. Exp. Eye Res. 72 163-172 (2001). 

It exerts its haemostatic action by reducing capillary fragility, and is indicated in epistaxis, haematuria, retinal... 

Systemic glucocorticoid treatment can cause severe exacerbation of bullous exudative retinal detachment and lasting visual loss in some patients with idiopathic central serous chorioretinopathy (SEDA-20, 374 68). The atypical presentation of this condition can include peripheral retinal capillary nonperfusion and retinal neovascularization. The treatment of choice in patients with idiopathic central serous chorioretinopathy is laser photocoagulation. 

Hainsworth DP, Katz ML, Sanders DA, Sanders DN, Wright EJ, Sturek M. Retinal capillary basement membrane thickening in a porcine model of diabetes mellitus. 

The capillaries of the retina are lined by continuous, close-walled, endothelial cells, which are the primary determinant of the molecular selectivity that is the major function of the blood-retinal barrier. Bruch s membrane is a prominent structure associated with the retinal-vitreous barrier, yet it contributes relatively little to the barrier s filtration properties. 

Brimonidine also does not appear to alter retinal capillary blood flow or vasomotor activity of the anterior optic nerve. Measurements of blood flow velocities in central retinal, ophthalmic, nasal, and temporal posterior ciliary arteries do not change when 0.2% brimonidine is administered twice daily. When applied to human eyes, brimonidine appears to have little or no contralateral lowering effect on lOP. 

Because Treponema pallidum is sensitive to penicillin G, this antibiotic is the drug of choice for treatment of syphilis and syphilitic eye disease (see Table 11-1). Syphilitic eye disease can include interstitial keratitis (stromal inflammation and vascularization), episcleritis, scleritis, nongranulomatous or granulomatous iritis, iris papules (collections of dilated capillaries in the iris), chorioretinitis, papillitis, retinal vasculitis, and exudative retinal detachment. Probenecid can be added to procaine penicillin to decrease excretion of the penicillin by the kidneys, thus causing an increase in penicillin plasma levels. Penicillins are not used for the treatment of minor ocular infections such as blepharitis and conjimctivitis... 

Various other systemic chemotherapeutic agents have been associated with retinotoxic effects. Use of interferon-a, for example, has resulted in various retinal effects, including cotton-wool spot formation, macular edema, capillary nonperfusion, arteriolar occlusion, and intraretinal hemorrhage. Cisplatin and etoposide have induced retinal toxicity in both adults and children. 

Neighboring RPE cells are connected by tight]unctions that help to create the blood/retinal barrier separating the neuro-sensory retina from fenestrated capillaries in the choroid. The basement membrane of RPE, together with the adjacent basement membrane of the choroid, forms a structure known as Bruch s membrane. RPE cells possess a number of organic and ion transporters to help move polar molecules across the blood retinal barrier. These include transporters for amino acids, folate, ascorbic acid, myo-inositol, organic anions, glucose and lactate. 

Blood is supplied to the retina by the central retinal artery and choroidal blood vessels (Oyster, 1999). The central retinal artery arises from the ophthalmic artery, w hich in turn branches off the internal carotid artery. Upon entering the retina, the central retinal artery branches into deep capillary beds in the INL and superficial capillary beds in the GCL. Endothelial cells of retinal capillaries are joined by tight junctions, contributing to the blood/retinal barrier. There is litde or no autonomic regulation of the retinal circulation blood flow through these capillaries is instead primarily controlled by autoregulation (Wangsa-Wirawan and Linsenmeier, 2003). Retinal capillaries drain into the central retinal vein. 

Gitlin, J. and D Amore, P. (1983). Culture of retinal capillary cells using selective growth media. Microvasc. Res. 26, 74-80. 

Liversidge JM, Sewell HF, Forrester JV (1990) Interaction between Lymphocytes and cells of the blood-retina barrier Mechanisms of T lympohocyte adhesion to human retinal capillary endothelial cells and RPE cells in vitro. Immunology 71 390-396. 

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