The fluid produced by the eye is known as aqueous humour. It feeds the eye and keeps it under pressure. Aqueous humour flows from the ciliary body into the anterior chamber, then through the trabecular meshwork, spongy tissue at the front of the eye, and into a drainage canal (which is a dark blue region next to the trabecular meshwork.
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The fluid does not flow freely through the trabecular meshwork in open-angle glaucoma, causing an increase in intraocular pressure, optic nerve damage, and vision loss. The majority, but not all, types of glaucoma are characterised by high intraocular (eye) pressure. When some of the fluid (aqueous humour) produced by the ciliary body of the eye flows freely out of the eye, intraocular pressure remains normal. This fluid nourishes the eye while also keeping it under pressure.
Aqueous Humor Function
The following are the functions of aqueous humour:
Keeping the intraocular pressure and the globe's shape.
Supplying nutrients and oxygen to ocular tissue such as the posterior cornea, trabecular meshwork, and lens.
Metabolic byproducts are removed from intraocular cells.
The function of the aqueous humour is used to increase the amount of light that reaches the retina.
Aqueous Humor Production
On average, the ciliary body produces aqueous humour around 2.5 μl per minute. The three processes that play a part in this production include the following:
While diffusion and ultrafiltration are passive processes, they aid in the collection of ultrafiltrated plasma within the stroma of the ciliary body. After that, the ciliary body epithelium actively secretes aqueous fluid into the posterior chamber. A Na+/K+ ATPase hydrolyzes ATP for energy in this active process.
Water from the ciliary body's stroma follows the Na+/K+ ATPase as it actively transports Na+ ions into the posterior chamber of the eye.
It is important to note that the sympathetic nervous system influences aqueous humour secretion. The activation of beta-2 adrenoceptors as well as alpha-2 adrenoceptors increases and decreases the production of aqueous humour, respectively.
What are the Chambers of the Eye?
The anterior chamber, posterior chamber, and vitreous chamber are the three chambers of your eye. The vitreous chamber is the large chamber at the back of your eye; the anterior chamber is the space between your cornea and iris, and the posterior chamber is the space between your iris and your eye's lens.
Aqueous humour fills both the anterior and posterior chambers.
Aqueous Humor Drainage
The aqueous fluid drains from the AC through the trabecular meshwork into the canal of Schlemm, which then drains to the episcleral veins. Schlemm's canal (SC) is a circular structure in the scleral sulcus, just behind the corneoscleral junction, that looks like a lymphatic vessel. The inner wall of the SC communicates with the AC, while the outer wall communicates with the episcleral veins.
While the trabecular meshwork drains the majority of aqueous humour, the uveoscleral route drains about 10% of it. The aqueous humour flows across the iris as well as the anterior side of the ciliary muscle into the suprachoroidal space, which is a space between the sclera and choroid.
Aqueous Humor Location
The anterior and posterior chambers of the eye contain aqueous, thin, watery fluid. The anterior chamber is located between the iris (the coloured part of the eye) and the cornea's inner surface (the front of the eye). The posterior chamber is behind the iris and ahead of the lens.
A large portion of the eyeball is made up of vitreous humour. It is a clear gel-like substance found behind the lens and in front of the retina at the back of the eye.
Composition of Aqueous Humor
Aqueous humour's composition is directly related to its function within the eye.
The ultrafiltration of the aqueous humour by the ciliary body produces nearly protein-free liquid, providing an optically clear medium for vision.
The high lactate level is caused by anaerobic glycolysis by cells of the anterior eye segment, such as the lens epithelium. The high concentration of ascorbic acid protects against UV-radiation, which can result in the formation of free radicals.
How Does Aqueous Humor Work?
Without getting too technical, the ciliary body constantly produces aqueous humour (located in the anterior chamber near the lens of the eye). For proper functioning, the production must be balanced by drainage at an equal rate.
Even minor changes in the production or outflow of aqueous humour are significant because they have a big impact on your intraocular pressure.
When intraocular pressure rises, it can cause glaucoma, a leading cause of vision loss.
Aqueous and Vitreous Humor
Vitreous is a clear substance that is 99 percent water. The remaining 1% is collagen and hyaluronic acid, which give vitreous a gelatinous consistency. The vitreous, in addition to maintaining the shape of the eye, absorbs shocks as well as keeps the retina properly connected to the back wall of the eye. On its way to the retina, the light passes through the vitreous.
In children, the consistency of the vitreous is similar to that of egg whites. It becomes more liquid as people age. The retina can separate from the back wall of the eye due to thinning vitreous, resulting in floaters — spots that appear to float in the field of vision. This separation is known as posterior vitreous detachment, and it affects the majority of people by the age of 70. As long as no retinal tearing occurs, this condition usually resolves on its own.