Kuhnt intermediary tissue as a barrier between the optic nerve and retina

Abstract

Utilizing adult albino rats and lanthanum nitrate as a tracer, electron microscopic studies were done to provide additional information on the blood-optic nerve barrier. Following injection into the cervical artery, lanthanum was observed to fill the intercellular space of the optic nerve parenchyma. Diffusion from the prelaminar optic nerve into the juxta-optic nerve retina was, however, prevented by the Kuhnt tissue at the level of the rod and cone layer. In this region, tight junctions were found between the glial cells of the Kuhnt intermediary tissue and were continuous from the tight junctions of the retinal pigment epithelial cells to the junctions (zonulae adhaerentes) of the outer limiting membrane. From the level of the outer limiting membrane to the inner limiting membrane there was no diffusion of lanthanum into the adjacent retina despite the absence of tight junctions, and the lanthanum which had diffused from the choroid was never observed in the area of the inner limiting membrane of the optic nerve head. It is in this region that the functional barrier may exist.

Detection of mild papilloedema using spectral domain optical coherence tomography

“…In normal conditions, there is no leakage into the peripapillary subretinal space because of the barrier property of the intermediary tissue of Kuhnt 15 17. Disruption of Kuhnt tissue results in a leakage from the optic nerve head into the peripapillary subretinal space.…”

The Glial Design of a Teleost Optic Nerve Head Supporting Continuous Growth

“…It is possible that these astroblasts constitute a source for the maintenance of the glial population in the optic nerve because they are con-stantly needed to support the newly formed ganglion cells' axons. In animals with a lamina cribrosa, there is a group of cells known as Kuhnt intermediary tissue, formed only by mature astrocytes, at the same location where the pool of astroblasts has been found (Okinami et al 1976;Triviño et al 1996;Schuck et al 2000). Similarly to the astroblasts of tench, these astrocytes also form a barrier between the retina and the optic nerve.…”

“…The glial elements that populate the NFL are Müller cells' processes, astrocytes, and microglial cells (Ogden 1978;Büssow 1980;Schnitzer 1985;Reichenbach and Robinson 1995;Vecino et al 1997;Lillo et al 1998). The optic disc has been widely studied in mammals (Okinami et al 1976;Büssow 1980;Morrison et al 1988;Hirata et al 1991;Ye and Hernández 1995;Triviño et al 1996;Fujita et al 2000;Hernández 2000), but little is known about the glial cytoarchitecture of this part of the ONH in other vertebrates (Springer and Mednick 1986;Dávila et al 1987;Prada et al 1989;Vecino et al 1997;Ott et al 1998;Schuck et al 2000). Nevertheless, several divergences among the glial cells from the ONH and the rest of the optic nerve were included in those studies.…”

Chemoarchitecture of glial fibrillary acidic protein (GFAP) and glutamine synthetase in the rat optic nerve: An immunohistochemical study

“…The tracer, lanthanum nitrate, freely diffused into the optic disc mainly along the perivascular space after an intravitreal injection, and was clearly observed in the intercellular space of optic nerve fibers to the level of the pigment epithelium 46) .…”

“…horseradish peroxidase and lanthanum nitrate) from the choroid into the optic nerve was observed, whereas the penetration of these tracers from the optic nerve into the retina was hardly seen [45][46] .…”