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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
The aqueous humour is a clear watery fluid that fills the anterior chamber. The lens is a biconvex transparent structure assisting in the focusing of light onto the retina and separates the anterior and posterior chambers. The vitreous humour occupies the posterior chamber and together with the aqueous humour acts as a refractive medium, maintaining the shape of the eyeball, and helps to hold the retina in contact with the choroid. The optic nerve is formed at the optic disc and leaves the orbital cavity via the optic foramen to the middle cranial fossa.
Chronic Hyperglycemia Impairs Vision, Hearing, and Sensory Function
Published in Robert Fried, Richard M. Carlton, Type 2 Diabetes, 2018
Robert Fried, Richard M. Carlton
The aqueous humor exits the eye through the drainage angle, which is the angle formed inside the anterior chamber between the iris and the peripheral cornea. The aqueous humor filters through this angle and through the sclera, the white part of the eye, and then joins with the network of veins outside the eye. Any disruption of this outflow of aqueous humor can result in an increase in intraocular pressure.
Special Senses
Published in Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard, Toxicologic Pathology, 2018
Kenneth A. Schafer, Oliver C. Turner, Richard A. Altschuler
Aqueous humor is continuously produced by the ciliary processes. It forms in the posterior chamber, flows through the pupil, enters the anterior chamber, and exits through the filtration angle. The filtration angle contains a porous pectinate ligament extending from the root of the iris to the termination of Descemet’s membrane. Aqueous flows through spaces of the uveal and corneoscleral meshwork and into the angular aqueous plexus or canal of Schlemm (humans and nonhuman primates, rabbit, and rodents) (Teixeira and Dubielzig 2013). Any blockage in this continuous flow of aqueous humor causes intraocular pressure (IOP) to rise.
Enhanced Ectasia Screening in Patients with Uveitis and Isolated Systemic Inflammatory Disease
Published in Ocular Immunology and Inflammation, 2022
Ibrahim Toprak, Ebru Nevin Cetin, Selen Akbulut, Gokhan Pekel, Selcuk Yuksel, Veli Cobankara
In the uveitis group, most of the patients with KC (66.7%) and KC suspect (65%) had no SID and no significant relation was detected between topographic classification vs. type of uveitis, number of uveitis attacks and uveitis duration since the initial diagnosis. However, the presence of uveitis with or without SID might be important for showing a higher autoimmune propensity to react to ocular self-antigens, as well as an increased likelihood of damage to ocular tissues. Furthermore, the accumulation of inflammatory mediators in aqueous humor and tear, which are the major metabolic supplies for cornea, can also lead to ultrastructural corneal damage.23–26 On the other hand, topical corticosteroid treatments for recurrent uveitis attacks might also lead alterations in corneal collagen structure, since corneal thinning effects of corticosteroids are well established.
Multiplex protein analysis for the study of glaucoma
Published in Expert Review of Proteomics, 2021
The utilized multiplex technologies to profile protein expression accelerate early detection and monitoring of the molecular alterations in intraocular biofluids like aqueous humor. However, collection and storage of intraocular biofluids require standardized procedures for protein analysis and data interpretation. With regard to aqueous humor sampling, avoiding to touch the tissues surrounding the anterior chamber, such as lens, iris, and corneal endothelium, is particularly important, as tissue injury may result in the elevation in aqueous humor proteins and cytokines [108]. This aspect is supported by the cytokine increase detected in eyes with previous intraocular surgeries, which can apparently induce the elevation of aqueous humor cytokines over the years in a chronic fashion [76,87,94,95]. As another related concern to underline, many previous studies did not correct the aqueous humor titers of cytokines to total protein concentration in individual samples, or did not consider their relation to blood cytokines. In fact, systemic inflammatory conditions and elevation of serum cytokines may affect aqueous cytokine titers through a leakage or breakdown of the blood-aqueous barrier. It is for this reason that a coefficient reflecting the ratio of aqueous humor to serum levels is used in the studies of ocular inflammatory diseases for proper comparisons [109,110]. Further consideration of these facets is needed to clarify whether iris damage might influence the aqueous humor levels of cytokines in previous glaucoma studies.
Current methods and new approaches to assess aqueous humor dynamics
Published in Expert Review of Ophthalmology, 2021
Carol B. Toris, Meghal Gagrani, Deepta Ghate
Invasive methods to measure aqueous flow are done mainly in mice. These methods include the dye dilution technique [50] and the constant flow infusion technique [51]. For the dye dilution technique, a dye is placed into the anterior chamber and its mass is measured over time. One microneedle connected to an aspiration system and a second microneedle connected to an infusion system are inserted into the anterior chamber. A dye (usually a fluorescent tracer) is infused into the anterior chamber at a set rate through the infusion needle and aqueous humor is removed at the same rate through the aspiration needle. The perfusion pressure is set at episcleral venous pressure, which in the mouse is approximately 9 mmHg. This pressure at which the outflow through the trabecular meshwork is zero. Over time, the fluid infused into the eye is diluted by secreted aqueous humor. The aspiration tubing filled with the diluted tracer is cut into segments of a certain length containing a set volume. The fluorescence of the fluid aspirated from the tubing is measured with a spectrofluorometer. The magnitude of tracer dilution over time is a measure of aqueous flow [50].