HOW
DO TEARS NORMALLY FUNCTION?
Tears are made primarily by the lacrimal gland,
which is anatomically located under the outer
one-third of the upper eyelid. With each blink,
the eyelid spreads tears over the surface of the
eye and pumps excess tears towards ducts in both
the upper and lower eyelids. These ducts then
drain the tears into the nose via the nasolacrimal
duct.
WHAT CAUSES TEARING DISORDERS?
Epiphora, or watery eyes, can be congenital or
acquired.
Congenital lacrimal duct obstruction (in either
one or both eyes) occurs in approximately 20%
of infants. This percentage is even higher in
premature babies. In most infants, the obstruction
is caused by a membrane at the base of the tear
duct just before the duct enters the nose.
Acquired (adult-onset) nasolacrimal duct obstruction
can be caused by several factors. Involutional
(age-related) nasolacrimal duct obstruction is
the most common cause. Other causes include trauma,
sinus disease, nasal polyps, tumour or infection.
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