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Results for “Human retina”

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At least 19 recordsLinked to original sources
PubMed1976

[Centrifugal fibers in the human retina].

The examination of 16 human retina stained in toto according to the Gallego method (1953) demonstrated the presence of centrifugal optic fibers. These fibers appear as large argyrophilic axons and can be traced as of the papille, amongst the centripetal optic fibers. The centrifugal fibers show a high degree of ramification which may extend over a quarter of the total retinal surface and terminate in the internal plexiform layer. Elsewhere the existence of perivascular and intravascular axon terminals as well as short axon ganglion nerve cells were demonstrated.

Humans↗
PubMed1977

Pigment epithelial ensheathment and phagocytosis of extrafoveal cones in human retina.

The association between extrafoveal cone outer segments and pigment epithelial cells was studied by transmission electron microscopy in three human retinas; ages 5,45 and 60. The pigment epithelial apical surface from a fourth human retina, age 38,was viewed in the scanning electron microscope. Multiple villous-like apical processes protrude from the pigment epithelium into the space above each cone. Sometimes one or more of these processes is sheet-like in form and contains a wealth of intracellular organelles, including mitochondria. One or more of the villous-like procesess reaches the cone and expands to ensheath the upper one-third of the outer segment. Llike vertebrate rods, extrafoveal human cones shed their terminal disks in packets and these packets are phagocytosed by the ensheathing apical processes. The phagosomes then ascend in the processes toward the pigment epithelia soma. Digestion of phagosomes appears to begin in the apical processes.

Adult↗
PubMed1979

A comparative histopathological study of argon and krypton laser irradiations of the human retina.

A series of comparative exposures to both argon and krypton lasers have been made at 3 locations in a human retina--the fovea, the macula, and intraretinal vessels. In the fovea argon irradiations resulted in damage to both the inner and outer retinal layers as a result of absorption within the pigment epithelium and the macular pigment, while krypton exposures damaged the outer retina and the choroid. In the macula both systems resulted in damage to the outer retina, and again sufficient krypton radiation passed into the choroid to induce blood vessel occlusion, haemorrhage, and oedema. When intraretinal vessels were irradiated, only with argon was sufficient energy absorbed within the vessels to damage them or their surroundings in the inner retina. The implications of these findings are discussed in relation to the therapeutic uses of lasers.

Argon↗
PubMed2026

Single-cell analysis of the human retina reveals stage-linked microglial states and neural-immune circuit rewiring in diabetic retinopathy.

Diabetic retinopathy (DR) is a major cause of vision loss worldwide. Here, we conduct single-cell RNA sequencing of twenty human retina samples (from living and post-mortem donors) across non-diabetic, diabetic, and DR states to create a comprehensive transcriptomic atlas. We identify two stable microglial populations-homeostatic and inflammatory-that exist along a functional continuum, plus a neutrophil cluster within C1QA+ myeloid cells with dynamic transitions occurring throughout disease progression. Module-level analysis reveals divergent transcriptional trajectories: homeostatic microglia maintain energetic programs while selectively upregulating stress elements, whereas inflammatory microglia layer additional pro-inflammatory programs onto preserved biosynthetic foundations. Eleven co-expression modules organize into two major axes: an inflammatory-stress axis, and a regulatory/metabolic-motility axis, with a stable translation module persisting across disease stages. Cell communication analysis further highlights sophisticated neural-immune interactions, particularly between photoreceptors and microglia. Our findings provide insights into the complex cellular dynamics of DR progression and suggest potential therapeutic targets for early intervention.

Humans↗
PubMed1979

A light microscopic study of the developing human neural retina.

Human embryonic and fetal eyes from 4 mm to 200 mm crown-rump length (26 days to 21 weeks of gestation) were studied in 0.75-micron sections impregnated with silver and toned with gold. The layer of Chievitz was formed by an inward migration of ganglion-cell and Müller-cell nuclei from the outer neuroepithelium and then, after further changes in nuclear location, the layer of Chievitz was cleared of ganglion-cell nuclei to become the definitive inner plexiform layer. Müller-cell nuclei later populated all retinal layers in the fetus. The argyrophilic Müller-cell cytoplasm associated with neuronal development is discussed in relation to glia-neuron interactions, with emphasis on the particular needs of retinal tissue.

Fetus↗
PubMed1977

Acoustic microscopy of the human retina and pigment epithelium.

An acoustic microscope uses sound waves rather than light to image a sample, and displays viscoelastic rather than optical properties. The Stanford instrument, operating at frequencies near 1,000 MHz, achieves resolution and magnification that is comparable to a light microscope. Using this instrument, we examined sections of normal human retina and pigment epithelium and found that characteristic degrees of acoustic attenuation or phase shift were produced by structures such as cell nuclei, rod and cone outer segments, Bruch's membrane, red blood cells, and ocular pigment. Resolution was better with thin than thick sections, and fixation did not significantly alter the acoustic properties of the tissues studied. A comparison of iris tissue from albino and pigmented rabbits showed that melanin was a particularly strong acoustic attenuator. Acoustic microscopy may provide a new and direct means of probing the physical structure of tissues and cells.

Acoustics↗
PubMed1979

Arterial bifurcations in the human retina.

The branching angles and relative diameters of blood vessels in 51 arterial bifurcations in the retina of a normal human eye were measured. In eight other bifurcations, only the total branching angles were measured. The results are compared with theoretical predictions in an attempt to understand the physiological principles governing branching in the cardiovascular system.

Adult↗
PubMed1977

Macrophage infiltration in the human retina.

The retinal tissues were examined by light microscopy and by scanning and transmission electron microscopy in a human eye in which there was extensive infiltration by macrophages. The stimulus to macrophagic infiltration was an immune response in a mixed sympathetic and lens-induced ophthalmitis which occurred after surgical treatment for glaucoma. The inflammatory infiltrate was so exuberant that the cells were considered to be predominantly exogenous and the sites of entry into the eye included the pars plana, the optic disc, and the retinal and choroidal blood vessels. Within the retina it appeared that the macrophages migrated via the nerve fibre layer and via the subretinal and subpigment epithelial spaces.

Glaucoma↗
PubMed1975

Histopathology of ruby and argon laser lesions in monkey and human retina. A comparative study.

Suprathreshold fundus lesions produced by ruby and argon laser photocoagulation were studied within 24 hours by light and electron microscopy. It was shown that damage was maximal in the outer retina in all ruby laser lesions and extramacular argon laser lesions. In both monkey and human, inner retinal damage occurred independently of outer retinal damage in macular lesions produced by the argon laser. In lesions produced by equal energy, inner retinal damage was more severe in humans than in monkeys. In both species outer retinal damage was less severe in the foveal than the parafoveal region and this disparity was greater in humans than in monkeys. These findings are important to the therapeutic use of argon laser energy for mascular disease. In particular, absortion of energy in the inner retina reduces the energy available in the treatment of subretinal lesions in the foveal area, and causes unwanted neuroretinal damage. The higher sensitivity to argon laser irradiation of the human fovea compared with the monkey fovea, has not been appreciated when defining laser safety limits.

Animals↗