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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.

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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.

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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.

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Embryology

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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.

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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 (Figure 24–2).

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FIGURE 24–2
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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.)

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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 through ...

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