21. Aqueous humor:
a. is mainly produced by the non-pigmented epithelium of the
pars
plana
b. is only produced by active transport mechanisms
c. is actively extruded into the lateral intercellular channels at a
constant rate
d. is kept optically clear by the tight junctions between the
endothelial cells of the iris capillaries and of
the non-pigment
epithelium
e. when nascent, is hypertonic compared to anterior chamber
aqueous
22. The composition of aqueous humor:
a. is solely dependent on the nature of the freshly secreted
fluid
b. is slightly hypertonic compared to plasma with respect to
concentrations of sodium, potassium and bicarbonate
c. has a very low concentration of ascorbic acid
d. is lower in glucose concentration, but higher in lactate
concentration when compared to plasma
e. contains low levels of amino acids, but high levels of protein when
compared to plasma
23. Intraocular pressure:
a. remains constant if aqueous production is constant
b. has a population distribution that is skewed to the right
c. is decreased when acetazolamide is administered, by decreasing
the rate of sodium and bicarbonate transport into
the posterior
chamber
d. can be increased by use of long term steroids
e. is usually measured by indentation at the slit lamp
24. The vitreous:
a. has an anterior cup known as the lenticular fossa
for the posterior
surface of the lens
b. contains a channel running antero-posteriorly that contained the
hyaloid artery, a branch of the central retinal
artery, that nourished
the lens in utero
c. is strongly attached to the vitreous base, which extends from the
ora serrata to the pars plana
d. is attached to the posterior lens capsule by Wieger’s ligament
e. is immediately related to Retinal Pigment Epithelium
25. The extraocular muscles:
a. are of skeletal type
b. consist of muscle bundles which are made up of many fibres that
are approximately 100-300 microns in diameter
c. are covered in a fibrous sheath called epimysium from their origin
to their insertion, that is continuous with Tenon’s
capsule
d. take their origin from rhe common tendinous ring
e. have dense innervation for fine control of eye movements