Central nervous system
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha in Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
The eye is the special sense organ of sight (Figs 11.52a,b). It is situated in the orbital cavity, surrounded by adipose tissue that affords protection from trauma. It is almost spherical with an anterior bulge, comprising three layers: an outer fibrous layer, a middle vascular layer and an inner nervous layer. It contains three substances: the aqueous humour, the lens and the vitreous humour. The outer fibrous layer forms a complete sphere, the anterior one-sixth is known as the cornea and the posterior five-sixths the sclera. It has no blood supply but derives its nourishment from lymph. The middle vascular layer forms nine-tenths of a sphere incomplete anteriorly. It comprises the choroid, ciliary body and the iris. The innermost layer forms three-quarters of a sphere (posteriorly) and is known as the retina. This has an outer pigmented layer and an inner nervous layer. It contains special cells designed for vision – rods and cones. The optic disc (or blind spot) is that part of the retina where the optic nerve enters the eyeball.
Optic nerve
Fiona Rowe in Visual Fields via the Visual Pathway, 2016
The intraorbital portion of the optic nerve includes the optic disc and the portion of the optic nerve within the posterior scleral foramen. The optic disc is the commencement of the optic nerve. It is approximately 1.5 mm in diameter and is significantly paler in colour than the surrounding retina. The optic disc is located about 3 mm nasal to and about 0.8 mm above the fovea. It is composed of axons of ganglion cells that leave the eye through the lamina cribrosa. The optic disc is oval in shape and the optic cup is a funnel-shaped depression within the disc where the central retina vessels enter and leave the eye. There are no ganglion cell axons in the optic cup (see Figure 5.1). The layers of the retina and choroid terminate at the edge of the optic disc and the absence of photoreceptors in this area explains the blind spot of the visual field. Posterior to the optic disc, the nerve fibres become myelinated.
The Problems
John Greene, Ian Bone in Understanding Neurology a problem-orientated approach, 2007
A normal optic disc is shown in 94a. Myopia makes the disc look enlarged and pale, and hypermetropia makes it look pink and small. Fundal examination in the acute phase of optic neuritis is usually normal but sometimes shows swelling of the optic nerve head (papillitis) (94b). Swelling may also be seen in AION, often associated with pallor and haemorrhages in the arteritic form. Optic disc swelling in the presence of normal visual acuity is typically papilloedema (94c), which should be presumed to be due to raised intracranial pressure unless proved otherwise. Optic atrophy (94d) is the end stage of a range of different optic nerve pathologies.
Quantitative Study of Human Scleral Melanocytes and Their Topographical Distribution
Published in Current Eye Research, 2020
Dan-Ning Hu, Shen Yao, Codrin E. Iacob, Jerome Giovinazzo, Richard B. Rosen, Hans E. Grossniklaus, Jodi Sassoon
Each H&E-section and S-100 stained section was examined microscopically at 100x − 400x magnification by a senior masked reviewer using an Olympus BH2 microscope. In the H&E section, the fibroblasts were recognized by the blue-colored oval nuclei and pink-colored cytoplasm and the melanocytes were recognized as cells with pigment granules in the cytoplasm. In S-100 stained sections, the melanocytes were stained red by AEC, whereas fibroblasts remained unstained by AEC. The numbers of these two cell types were counted in a high magnification (400 X) rectangle field (360 μm x 450 μm, 0.16 mm2). The density of cells was expressed as cell number/mm2 (equal to cell number per high magnification area timed 6.25). Melanocytes and fibroblasts were counted in 10 randomly selected fields (x 400) in each of the anterior, equatorial and posterior areas. The anterior areas began 1 mm behind the Schwalbe’s line and extended 4 mm posteriorly. The equatorial areas began 2 mm anterior to the equator and extended 4 mm posteriorly. The posterior area was a circular region extending 4 mm from the margin of the optic disc
Melanocortin 5 Receptor Expression and Recovery of Ocular Immune Privilege after Uveitis
Published in Ocular Immunology and Inflammation, 2022
Tat Fong Ng, Ambika Manhapra, David Cluckey, Yoona Choe, Srujan Vajram, Andrew W. Taylor
Enucleated eyes from EAU mice with or without treatment were fixed in Davidson’s fixative for 24 hours and then transferred to 10% buffered formalin for an additional 24 hours. The eyes were subsequently embedded in paraffin, after which 5-µm sections were cut and stained with H&E. The images were taken using a CX33 microscope (Olympus) and QColor 5 camera system and software (Olympus). Presented are the retinal sections at two optic disk diameters from the center of the optic nerve. Thickness of the retina and the outer nuclear layer (ONL) were measured using ImageJ software of full-length retinal sections centered on the optic nerve (representative images in Supplemental Figure 2). Measurements were made at 0.5, 1.0, 1.5, 2 mm to the right and left (−0.5, −1.0, −1.5, −2 mm) of the optic nerve head.
Sympathetic Ophthalmia - An Overview
Published in Ocular Immunology and Inflammation, 2023
Mamta Agarwal, Aleksandra Radosavljevic, Mudit Tyagi, Francesco Pichi, Aisha A. Al Dhanhani, Aditi Agarwal, Emmett T. Cunningham
FA in SO demonstrates a delay in choroidal perfusion seen as choroidal hypofluorescence during the acute uveitic phase.91 Usually, the optic disc shows leakage from the disc vessels or staining of the nerve head. Vascular leakage can also be seen. In the acute phase of SO, two patterns of FA can be identified. Most commonly, multiple, bilateral, pinpoint hyperfluorescent dots at the level of the RPE are visualized during the early and mid-phase of the study, corresponding to the RPE bumps over the OCT undulations.98 In the late phase of the angiography, there is an increase in the fluorescence intensity that gradually enlarges and leaks with pooling of dye in the sub-membranous spaces (Figure 3).100,101 The pattern with initial pinpoint hyperfluorescent leaks is seen more frequently and is virtually identical to that seen in the acute phase of VKH disease.