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Impact of Retinal Stimulation on Neuromodulation
Published in Yu Chen, Babak Kateb, Neurophotonics and Brain Mapping, 2017
The most familiar of the retina’s ten layers is the one with photoreceptors, split into the outer and inner segments of rods and cones. Photoreceptors need nourishment from another retinal layer, the retinal pigment epithelium (RPE). The constant interaction between the RPE and the rod photoreceptors is termed the visual cycle, triggered by lighting changes. Cones have a chemical interchange with Mueller cells. The external limiting membrane (or outer limiting membrane) separates the cell bodies of the photoreceptors from their outer and inner segments. The line of cell bodies is termed the outer nuclear layer of the retina. Oftentimes, a photoreceptor integrity line is evaluated on retinal imaging, but it is not a retinal layer. It simply represents the junction between the outer and inner segments of the photoreceptors, and its assessment is useful for determining the progress of various diseases.
Modeling Neuroretinal Development and Disease in Stem Cells
Published in Deepak A. Lamba, Patient-Specific Stem Cells, 2017
The retina is the main light-sensing region of the eye. The light sensing is carried out by a group of cells lining the back of the retina called the photoreceptors. The cells are involved in the conversion of the light signal into a chemical signal by the process of phototransduction, which is passed onto the downstream inner retinal neurons. The retina has three main cellular layers: the outer nuclear layer where the photoreceptors reside; the inner nuclear layers, which contain the main excitatory inner neurons called the bipolar cells along with two types of inhibitory interneurons called the horizontal and amacrine cells; and finally, the ganglion cell layer, which contains the retinal ganglion cells (RGCs) whose axons project to the central visual cortical areas (Figure 11.1). As stated previously, photoreceptors are the light-sensing cells of the retina. There are two main types of photoreceptors in the vertebrate retina, the rod and the cone. Cone photoreceptors are born earlier than the rods and are critical for high acuity vision and crowd the central part of the retina. One of the earliest photoreceptor genes expressed is cone–rod homeobox gene (Crx) (Furukawa et al., 1997). Following specification, the photoreceptors take up either a rod or a cone fate. The cone photoreceptors subsequently decide between short and medium wavelengths (and long wavelength in Old World primates like humans) (Hunt et al., 1998).
Annotated retinal optical coherence tomography images (AROI) database for joint retinal layer and fluid segmentation
Published in Automatika, 2021
Martina Melinščak, Marin Radmilović, Zoran Vatavuk, Sven Lončarić
To detect IRF, SRF, and PED, the knowledge of their location within or outside specific retinal layers can be used to facilitate their detection and differentiation. The retina is histologically divided into 10 layers: (1) internal limiting membrane (ILM), (2) retinal nerve fibre layer (RNFL), (3) ganglion cell layer (GCL), (4) inner plexiform layer (IPL), (5) inner nuclear layer (INL), (6) outer plexiform layer (OPL), (7) outer nuclear layer (ONL), (8) external or outer limiting membrane (ELM or OLM), (9) photoreceptor layer, and (10) retinal pigment epithelium/Bruch’s membrane complex (RPE/BM). The layers visible in the OCT scan have been correlated to these histological layers, with the exception of a few additional zones observed in the photoreceptor layer for which the exact histological counterpart is not yet defined [36].
Fish-oil supplementation improves retinal injury induced by diabetes and hypercholesterolemia in male Wistar rats
Published in Egyptian Journal of Basic and Applied Sciences, 2020
Hassan IH El-Sayyad, Doaa A. Ali, Mohamed E Hanafy
At the ultrastructural level, the control and those supplemented with fish oil showed normal retinal cell layers. The pigment epithelium is firmly attached to the Bruch’s membrane with underlying choriocapillaris lined by flattened endothelial cells. The apical cell surfaces have a fine arrangement of microvilli which takes as irregular-shaped structures. The basal cell membrane is irregular and in-folded (Figure 2(a)). The photoreceptors of outer segments are inter-digitated with microvilli of the pigment epithelium. Their cell bodies consist of frequently traversed regular-stacked thin membranes (Figure 2(b)). The outer nuclear layer is composed of closely packed nuclei of the photoreceptors and distinguished by its distinctive rosette-shaped thick heterochromatin and the very thin coat of cytoplasm (Figure 2(c)). Internally, the inner nuclear layer is distinguished by two major types of cells; horizontal and bipolar cells (Figure 2(d)). The ganglion cells vary in size with centrally located nuclei composed mainly of euchromatin. At its periphery and in between the ganglion cells, nerve fibers are distributed (Figure 2(e)).