Disorders of the lacrimal system are among the most common problems
encountered in pediatric ophthalmology. Approximately 6% of
infants are born with nasolacrimal duct obstruction (NLDO). Many
of these will improve spontaneously, but because NLDO is so common,
lacrimal surgery is one of the most frequent surgical procedures
performed by pediatric ophthalmologists.
The lacrimal system functions by producing, distributing, and
eliminating tears. Tears are produced by the lacrimal gland in the
superolateral orbit, flow across the eye into the lacrimal puncta, travel
through the lacrimal canaliculi to the lacrimal sac, then into the
nares via the nasolacrimal duct (NLD) (Figure 24–1). The
contraction of the eyelid muscles creates a pumping effect, which facilitates
the normal drainage of tears.
Drawing of lacrimal system.
A proper tear layer is vital to ocular health for several reasons.
First, the natural flow of tears continuously rinses debris and
other irritants from the eyes. Second, a normal tear film is required
for comfort. Patients with dry eyes have recurrent symptoms of ocular
irritation. Third, the tear film is important for normal vision.
The tear film is the first surface that light rays come into contact with
on the eyes. A regular smooth surface is required to focus these
light rays properly. If the tear film is unstable, patients experience
intermittent blurred vision.
The lacrimal drainage system begins as a nest of ectodermal cells
at the site of the future lacrimal sac. Cords of cells extend from
this site to the eyelids and into the nares. Canalization of this
tissue results in the formation of the lacrimal sac, canaliculi,
and NLD. This canalization begins at the lacrimal sac and extends
distally. The last portion to canalize is the opening of the NLD
into the nares.
NLDO is by far the most common lacrimal problem encountered in
children, occurring in approximately 6% of infants. It
results from incomplete canalization of the NLD during embryological development.
Because the opening of the duct into the nares is normally the last
portion to canalize, this is the most common site of obstruction
Nasolacrimal duct obstruction. The tears drain into the
nasolacrimal duct, where they encounter a membrane at the site of
obstruction, causing the tears to flow back to the eyelid and onto
the cheek. (Modified and reprinted with permission from Lueder GT.
Balloon catheter dilation for treatment of older children with nasolacrimal
duct obstruction. Arch Ophthalmol.
2002;120:1685–1688. Figure 1. Copyright American Medical
Association. All Rights Reserved.)
The blocked flow of tears produces 2 clinical problems. The first
is overflow tearing (epiphora). Because
the tears cannot drain into the nares, they back up ...