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Central nervous system
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
Both eyes should appear as roughly spherical structures. The transverse section through the normal eye as demonstrated in Figs 11.55b,c shows the eyelid, cornea, anterior chamber and the posterior chamber. This is behind the lens, and is occupied by the vitreous body or humour, sometimes known simply as the vitreous. The cornea is seen as a thin hypoechoic layer parallel to the eyelid. The anterior chamber is filled with anechoic fluid and is bordered by the cornea, iris and the anterior reflection of the lens capsule. The normal lens is anechoic, and the normal vitreous body is relatively echolucent in a young healthy eye. The evaluation of the retrobulbar area includes the optic nerve, extraocular muscles and bony orbit. Each optic nerve may be demonstrated as a hypoechoic structure approximately 2–3 mm thick, directed medially from the posterior aspect of the globe.
Development of Ophthalmic Formulations
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
Paramita Sarkar, Martin Coffey, Mohannad Shawer
Aqueous humor is a clear fluid that is secreted by the ciliary body via the filtration of blood passing through the ciliary body capillaries. It has several functions including maintaining the shape of the eye by controlling its pressure, providing nutrition to the cornea and lens, and providing transport of waste materials away from surrounding tissues. The aqueous humor is composed mainly of water; high concentrations of ascorbic acid, glucose, and amino acids; and limited levels of proteins. Aqueous humor flows from the ciliary body in the posterior chamber (behind the iris) into the anterior chamber (between the iris and the cornea). Aqueous humor flows out of the eye through the trabecular meshwork (a network of collagen fibers and endothelial-like trabecular cells) into Schlemm’s canal and through the uveoscleral route [24]. The entire volume of the aqueous humor is about 0.2 mL and is replaced every 1–2 h [19]. Maintaining the intraocular pressure (IOP) of 10–20 mmHg is a balancing act of production and drainage.
Designing for Head and Neck Anatomy
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
The eye is an approximate sphere with a 2.5 cm (1 in.) diameter (Forrester, Dick, McMenamin, Roberts, & Pearlman, 2016, p. 13). Refer to Figure 3.7 to study eye structures. When you look at a person’s face you see just a portion of the white sclera of the eyeball surrounding the colored iris and the dark central pupil. The cornea, the clear front window of the eye, lies in front of the iris and the structurally deeper crystalline lens. The sclera, but not the cornea, is covered by the conjunctiva, a thin mucous membrane which is the outermost layer of the exposed eyeball and contiguous with the inner layer of the eyelid. It effectively prevents the migration of small foreign bodies or liquids into the eye socket and the cranium. The eyeball is not one fluid-filled balloon-like structure. It actually has three chambers. The anterior chamber lies between the cornea and the iris and bulges slightly under the upper and lower eyelids. The smaller posterior chamber lies between the iris and the crystalline lens. The fluid in these two chambers is called the aqueous humor. The third chamber, the vitreous chamber, between the crystalline lens and the retina, at the posterior of the eye, holds a more viscous fluid, the vitreous humor.
Repeatability and reproducibility of anterior lens zonule length measurement using ArcScan insight 100 very high-frequency ultrasound
Published in Expert Review of Medical Devices, 2023
Zehui Zhu, Han Zou, Hongzhe Li, Xueer Wu, Yiyi Wang, Zhangliang Li, Yune Zhao
Most published studies using the Insight 100 have focused on phakic IOL implantation. Accurate measurements of the anterior eye segment’s anatomy play a critical role in selecting the appropriate IOL size before surgery [6,10,11]. Anterior segment optical coherence tomography (AS-OCT) and ultrasound devices are utilized for measuring various anterior segment structural parameters, including anterior chamber depth, anterior chamber angle distance, sulcus-to-sulcus, and other relevant metrics. AS-OCT enables swift image acquisition and high-resolution scans. However, it is limited by its inability to display the ciliary body, ciliary sulcus, and the complete space between the iris and the crystalline lens with clarity. In comparison to AS-OCT, the Insight 100 examination procedure is notably more intricate and requires additional time. However, the primary benefit of utilizing Insight 100 is its ability to produce highly precise images of the entire anterior ocular segment, which includes the ciliary muscle, the equator of the lens, and the posterior lens capsule.