Trabecular meshwork
Encyclopedia
The trabecular meshwork is an area of tissue in the eye
located around the base of the cornea
, near the ciliary body
, and is responsible for draining the aqueous humor from the eye via the anterior chamber
(the chamber on the front of the eye covered by the cornea).
The tissue is spongy and lined by trabeculocytes; it allows fluid to drain into a set of tubes called Schlemm's canal
flowing into the blood system.
The trabecular meshwork is assisted to a small degree in the drainage of aqueous humour by a second outflow pathway, the uveo-scleral pathway (5-10% of outflow occurs this way). The uveo-scleral pathway is increased with the use of glaucoma
drugs such as prostaglandins (e.g., Xalatan, Travatan).
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
located around the base of the cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
, near the ciliary body
Ciliary body
The ciliary body is the circumferential tissue inside the eye composed of the ciliary muscle and ciliary processes. It is triangular in horizontal section and is coated by a double layer, the ciliary epithelium. This epithelium produces the aqueous humor. The inner layer is transparent and covers...
, and is responsible for draining the aqueous humor from the eye via the anterior chamber
Anterior chamber
The anterior chamber is the fluid-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium. Aqueous humor is the fluid that fills the anterior chamber. Hyphema and glaucoma are two main pathologies in this area. In hyphema, blood fills the anterior chamber...
(the chamber on the front of the eye covered by the cornea).
The tissue is spongy and lined by trabeculocytes; it allows fluid to drain into a set of tubes called Schlemm's canal
Schlemm's canal
Schlemm's canal, also known as canal of Schlemm or the scleral venous sinus, is a circular channel in the eye that collects aqueous humor from the anterior chamber and delivers it into the bloodstream via the anterior ciliary veins....
flowing into the blood system.
Parts
The meshwork is divided up into three parts, with characteristically different ultrastructures:- Inner uveal meshwork - Closest to the anterior chamber angle, contains thin cord-like trabeculae, orientated predominantly in a radial fashion, enclosing trabeculae spaces larger than the corneoscleral meshwork.
- Corneoscleral meshwork - Contains a large amount of elastinElastinElastin is a protein in connective tissue that is elastic and allows many tissues in the body to resume their shape after stretching or contracting. Elastin helps skin to return to its original position when it is poked or pinched. Elastin is also an important load-bearing tissue in the bodies of...
, arranged as a series of thin, flat, perforated sheets arranged in a laminar pattern; considered the ciliary muscleCiliary muscleThe ciliary muscle is a ring of striated smooth muscle in the eye's middle layer that controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humour into Schlemm's canal. It changes the shape of the lens within the eye not the size of the pupil which is...
tendonTendonA tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
. - Juxtacanalicular tissue (also known as the cribriform meshwork) - Lies immediately adjacent to Schlemm's canal, composed of connective tissue ground substanceGround substanceGround substance is a term for the non-cellular components of extracellular matrix which contain the fibers.It is usually not visible on slides, because it is removed during the preparation process....
full of glycoaminoglycans and glycoproteins. This thin strip of tissue is covered by a monolayer of endothelial cells.
The trabecular meshwork is assisted to a small degree in the drainage of aqueous humour by a second outflow pathway, the uveo-scleral pathway (5-10% of outflow occurs this way). The uveo-scleral pathway is increased with the use of glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...
drugs such as prostaglandins (e.g., Xalatan, Travatan).
Role in Glaucoma
Glaucoma is thought to be caused by an increase in intraocular pressure. Pressure increases either when too much aqueous humor fluid is produced or by decreased aqueous humor outflow. The Trabecular meshwork is responsible for most of the outflow of aqueous humor.See also
- Argon laser trabeculoplasty
- GlaucomaGlaucomaGlaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...
- Intraocular pressureIntraocular pressureIntraocular pressure is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk from glaucoma...
- Ocular hypertensionOcular hypertensionOcular hypertension is intraocular pressure higher than normal in the absence of optic nerve damage or visual field loss.Current consensus in ophthalmology defines normal introcular pressure as that between 10 mmHg and 21 mmHg...
- TrabeculectomyTrabeculectomyTrabeculectomy is a surgical procedure used in the treatment of glaucoma to relieve intraocular pressure by removing part of the eye's trabecular meshwork and adjacent structures. It is the most common glaucoma surgery performed and allows drainage of aqueous humor from within the eye to underneath...
