The aqueous humor may be secreted into this space after beta-adrenergic agonist stimulation, but this notion requires additional studies [ 20 ]. The iris inserts into the anterior side of the ciliary body and separates the aqueous compartment into a posterior and anterior chamber. The angle formed by the iris and the cornea is the anterior chamber angle 6. The aqueous humor is formed by the ciliary process, passes from posterior chamber to the anterior chamber through the pupil, and leaves the eye at the anterior chamber angle.
The posterior wall of the scleral sulcus is formed by a group of fibers, parallel to the limbus that project inward like a fibrous ring, called the scleral spur.
The spur is attached anteriorly to the trabecular meshwork and posteriorly to the sclera and the longitudinal portion of the ciliary muscle [ 26 ]. When the iris inserts into the anterior side of the ciliary body, it leaves a variable width of the latter structure visible between the iris and scleral spur, corresponding to the ciliary body band.
Gonioscopically, it appears as a brownish band. The trabecular meshwork consists of connective tissue surrounded by endothelium. This tissue may be divided into three portions: a uveal meshwork, b corneoscleral meshwork and c juxtacanalicular tissue 6. By gonioscopy, the trabecular meshwork can be separated into two portions: an anterior named non-pigmented and a posterior pigmented. The inner layers of the trabecular meshwork can be observed in the anterior chamber angle and are referred to as the uveal meshwork.
This portion is adjacent to the aqueous humor, is arranged in bands or rope-like trabeculae, and extends from the iris root and ciliary body to the peripheral cornea. These strands are a normal variant and are called by a variety names such as iris process, pectinated fibers, uveal trabeculae, ciliary fibers, and uveocorneal fibers.
The deeper layers of the uveoscleral meshwork are more flattened sheets with wide perforations. The outer layers, the corneoscleral meshwork, consist of 8 to 15 perforated sheets. The corneoscleral trabecular sheets insert into the scleral sulcus and spur. These sheets are not visible gonioscopically. The perforations are elliptical and become progressively smaller from the uveal meshwork to the deep layers of the corneoscleral meshwork [ 28 ].
The ultrastructure of the trabecular, uveal and corneoscleral meshworks is similar. Each sheet is composed of four concentric layers. The trabecular beams have a central core of connective tissue of collagen fiber types I and III and elastin. There is a layer composed of elastic fibers that provides flexibility to the trabeculae. The core is surrounded by a glass membrane, which is composed of fibronectin, laminin, heparin, proteoglycan and collagen type III, IV and V.
The endothelial layer is a continuous layer and covers all the trabeculae. The endothelial cells are larger, more irregular than corneal endothelial cells.
They are joined by gap junctions and tight junctions and have microfilaments, including actin filaments and intermediate filaments vimentin and desmin [ 30 ]. It can be seen, by slit-lamp examination, as a fine white ridge, just anterior to the meshwork, and with an indirect contact gonioscopic lens, it is identified at the point where the anterior and posterior beams of the cornea converge parallelepiped method to identify the transition between the cornea and the meshwork.
Gonioscopically, it has an irregular roughened pigmented surface. Support for Caregivers. Questions to Ask About Cancer.
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The middle layer choroid, ciliary body and the iris is vascular. The innermost layer the retina is nervous or sensory. The fluids in the eye are divided by the lens into the vitreous humor behind the lens and the aqueous humor in front of the lens. The lens itself is flexible and suspended by ligaments which allow it to change shape to focus light on the retina, which is composed of sensory neurons.
The ciliary body is a ring of tissue that encircles the lens. Aqueous fluid or aqueous humor is the clear fluid in the eye that provides nourishment and helps the eye maintain its shape as well as healthy pressure levels. Each of these functions is essential for the health of the eye — in fact, conditions such as ocular hypertension and glaucoma can occur if too much aqueous fluid is produced by the ciliary body.
The aqueous humor — which is constantly produced by the ciliary body — drains through a channel called the trabecular meshwork , located at the angle where the iris and cornea meet.
There must be a balance between how much aqueous humor is being produced and how much is drained in order to maintain a healthy amount of pressure in the eye. This is known as the intraocular pressure IOP. Ocular hypertension is the term used to describe higher-than-normal IOP.
This elevated pressure can in turn lead to glaucoma — the term used to describe a group of related eye conditions that cause damage to the optic nerve and can lead to blindness if left untreated. Carbonic anhydrase inhibitors such as Azopt brinzolamide and Trusopt dorzolamide.
Alpha-adrenergic agonists such as Alphagan P brimonidine and Iopidine apraclonidine.
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