Aqueous humour


A transparent, watery fluid similar to plasma, but containing low protein concentrations.

It is secreted from the ciliary epithelium.

It is a structure supporting the lens.

It fills both the anterior and the posterior chambers of the eye.

Not to be confused with the vitreous humour, which is located in the space between the lens and the retina, also known as the posterior cavity or vitreous chamber.

Its composition includes amino acids transported by ciliary muscles, 98% water, with electrolytes of Sodium 142, Potassium 2.2 – 4.0, Calcium1.8 Magnesium 1.1 Chloride 131, HCO3- = 20, Phosphate 1, pH 7.4 Osm. 304, Ascorbic acid, Glutathione, and Immunoglobulins

The aqueous humour maintains the intraocular pressure and inflates the globe of the eye.

Its hydrostatic pressure keeps the eyeball in a roughly spherical shape and keeps the walls of the eyeball taut.

The aqueous humour provides nutrition for the avascular ocular tissues; posterior cornea, trabecular meshwork, lens, and anterior vitreous.

The aqueous humour may transport ascorbate in the anterior segment to act as an antioxidant agent.

The aqueous humour contains immunoglobulins that may indicate a role in immune response to defend against pathogens.

It provides for expansion of the cornea and increases protection against dust, wind, pollen grains and some pathogens.

Secreted into the posterior chamber by the non-pigmented epithelium of the ciliary body (pars plicata).

It is continually produced by the ciliary processes and this rate of production must be balanced by an equal rate of aqueous humour drainage.

Aqueous humor is produced in a continuous fashion by the ciliary body in the posterior chamber and drains into the anterior chamber of the eye. 

A majority of aqueous humor drains through the trabecular meshwork and a minority of aqueous outflow is drained through the uveoscleral pathway. 

Primary open-angle glaucoma is the most common type of glaucoma: characterized by increased resistance to drainage in the trabecular meshwork.

The drainage angle between the cornea and iris remains open in primary open-angle glaucoma.

5 alpha-dihydrocortisol may be involved in production of aqueous humour.

Even small variations in the production or outflow of aqueous humour will have a large influence on the intraocular pressure.

Aqueous humour drainage route is first through the posterior chamber, then the narrow space between the posterior iris and the anterior lens, through the pupil to enter the anterior chamber.

From the anterior chamber, the aqueous humour exits the eye through the trabecular meshwork into Schlemm’s canal.


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