China
Africa
Explore chapters and articles related to this topic
Basic Chemical Hazards to Human Health and Safety — I
Published in Jack Daugherty, Assessment of Chemical Exposures, 2020
The retina is the compact neural structure in the eye that is responsible for converting an ocular light image to a neural impulse that the brain can interpret. On the inside of the eye, the retina is normally protected from exposure to chemicals. Internally absorbed COCs can affect retina, causing lesions and other changes such as retinal edema or hemorrhage. A few COCs cause acute narrowing of the retinal arteries, leading to damage to the optic nerve with ultimate loss of vision. Below the retinal surface layer lies the ganglion cell layer, composed of neuron cell bodies extending to the mid-brain via the optic nerve. Some COCs act directly on the neural cell bodies, while others attack the optic nerve, such as methyl alcohol. The degree of loss of visual acuity depends on the severity of the exposure.
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).
Low-level occupational exposure to BTEX and dyschromatopsia: a systematic review and meta-analysis
Published in International Journal of Occupational Safety and Ergonomics, 2023
Younes Sohrabi, Fatemeh Rahimian, Esmaeel Soleimani, Soheil Hassanipour
The most common deficit in color discrimination in the BTEX-exposed subjects was in the blue–yellow axis, suggesting that the D-15d detects early neurotoxic effects of organic solvents [12–14,16,18,19]. Taking into account the subclinical nature of acquired dyschromatopsia, the D-15d has been regarded as the method of choice for neurotoxicity in human studies [30,37,38,54]. One study concluded that the total confusion index was more sensitive than the CCI in the evaluation of acquired dyschromatopsia [15]. While the findings of the cross-sectional studies regarding the dyschromatopsia in BTEX-exposed workers were consistent, the results of two studies investigating visual evoked potential, electroretinogram and contrast sensitivity were controversial [12,17]. Allam et al. [12] reported that prolonged occupational exposure to a mixture of organic solvents may affect the optic tract functions in the form of increased latency of visual evoked potential response, altered quality of color vision and decreased contrast sensitivity. They also concluded that such exposure may affect the retinal ganglion cell layer with increased latency of P50 of the pattern electroretinogram response. In contrast, Gong et al. [17] found no abnormalities in the visual evoked potential test in the exposed subjects with impaired color vision and contrast sensitivity Overall, these findings suppose that low-level exposures to mixtures of organic solvents might affect the retina and optic nerve. However, further studies are needed to substantiate whether such an impact affects Brodmann’s areas of the visual cortex in the brain.
Glaucoma Detection Using Optical Coherence Tomography Images: A Systematic Review of Clinical and Automated Studies
Published in IETE Journal of Research, 2022
Hina Raja, Muhammad Usman Akram, Taimur Hassan, Aneeqa Ramzan, Amtual Aziz, Hira Raja
The ganglion cell layer (GCL) analysis opens new ingresses in the field of neuro-ophthalmology for detecting and monitoring optic neuropathies. GCL analysis demonstrates a high correlation with perimetry, thus facilitating the future predications and staging of the disease [65]. Wang et al. [66] investigated the significance of retinal ganglion cell layer (GCL) thickness in a glaucoma patient using FD-OCT and manual segmentation. Horizontal scans were obtained from one eye of 20 and 26 control and glaucoma patients, respectively. Manual segmentation extracted various layers and their thicknesses were determined; patients were separated into two groups depending on their foveal sensitivity. The thicknesses of the RNFL and RGC+ inner plexiform layer (low sensitivity group) were less than that of the high sensitivity group. Furthermore, the thinning of RGC + IPL showed association with the loss in the visual field test (10–2). The conclusion was made that local measures of retinal ganglion cell layer thickness showed a qualitative agreement with the VF.
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].