Aqueous outflow is affected by the:
a. trabecular meshwork
the main bulk of aqueous drains through this pressure dependent system
the pressure difference between the intraocular pressure and the pressure
within the episcleral vessels affects the drainage
drainage increases with increased intraocular pressure and low episcleral
vessels and decreases with low intraocular pressure or high episcleral
vessels (as in Valsalva's manoeuvre or blockage of the superior vena cava)
the position of the iris can affect the flow of aqueous, when the pupil
is constricted, the trabecular meshwork opens wider and offers more areas
for active transport. Conversely, the iris in a dilated pupil can impede
the main resistant is offered by juxtacanalicular layer of the trabecular
aqueous enters the Schlemm's canal by a process of phagocytosis.
from the Schlemm's canal the aqueous leaves the eye via the episcleral
b. uveoscleral system
about 10 to 30% of aqueous drains through this system.
it is pressure independent
intercellular space between the ciliary muscle fibres and the loose connective
tissue of the suprachoroidal space.
aqueous reaches the suprachoroidal space and leave the eye either through
the sclera or large vessels leaving the sclera.