aqueous humour


Also found in: Dictionary, Thesaurus, Encyclopedia, Wikipedia.
Related to aqueous humour: vitreous humour

aqueous humour

The watery fluid filling the front chamber of the eye between the back of the CORNEA and the front of the IRIS.

aqueous humour

fluid that fills the space between the cornea and the lens of the vertebrate EYE (see Fig. 156 ).

humour, aqueous

Clear, colourless fluid that fills the anterior and posterior chambers of the eye. It is a carrier of nutrients for the lens and to a larger extent the cornea, especially of glucose and essential amino acids. It contributes to the maintenance of the intraocular pressure. It is formed in the ciliary processes, flows into the posterior chamber, then through the pupil into the anterior chamber and leaves the eye through the trabecular meshwork passing to the canal of Schlemm and then to veins in the intrascleral venous plexus (Fig. H3). A small amount (10% to 15%) also flows out of the eye via the uveoscleral pathway. The aqueous in the anterior chamber is a component of the optical system of the eye. It has an index of refraction of 1.336, slightly lower than that of the cornea, so that the cornea/aqueous surface acts as a diverging lens of low power. It is a fluid very similar to blood plasma but with a much lower concentration of protein and a higher concentration of ascorbate.The rate of aqueous humour outflow varies between 2.0 μl/min and 3.0 μl/min via both the conventional (trabecular meshwork and Schlemm's canal) and the unconventional (uveoscleral) pathways. This rate is normally equal to the rate of aqueous secretion. If the rate of outflow is lower than the rate of secretion intraocular pressure increases. See aqueous flare; ultrafiltration.
Fig. H3 Outflow of aqueous humourenlarge picture
Fig. H3 Outflow of aqueous humour
References in periodicals archive ?
They all increase aqueous humour outflow both via the uveoscleral route and may also increase trabecular outflow by varying degrees.
2]) selective agonists involves reduction of aqueous humour production and brimonidine also increases uveoscleral outflow.
Aqueous humour production and flow has been reported to be reduced in the eyes of people with DM, (1-4) with the severity being dependent on the degree of retinopathy.
d) Aqueous humour production is related to the degree of retinopathy
Aqueous humour is derived from the blood plasma of the capillaries within the ciliary processes of the ciliary body.
Following production, the primary aqueous humour enters the posterior chamber, behind the iris and in front of the crystalline lens, and passes through the pupil into the anterior chamber where it circulates prior to exiting the internal eye via the ACA.
At selected wavelengths, as for the aqueous humour, absorption occurs in the lens.
Table 1: Summary of typical damage to ocular tissue from IR exposure Ocular Structure Typical Damage Cornea Loss of transparency, opacification, haze, exfoliation, debris Aqueous Humour Flare Iris Swelling, cell death, miosis, hyperaemia/inflammation Lens Anterior opacities, sutures more visible Vitreous Humour Haze Retina Oedema, burns, depigmentation Table 2: Infrared sources and their detailed effects on the eye Wavelength Sources 400-700nm Sun, broad band arc lamps, flash and incandescent lamps 488, 514.