ABSTRACT
The punctum is a funnel-shaped structure surrounded by a ring of connective tissue that is approximately 0.2 to 0.3 mm in diameter. The upper and lower puncta open on a slight elevation of the posterior margin of the lid corresponding to the junction of the cilia and lacrimal portions of the lids. Inferior to the punctum is the vertical component of the canaliculus, which is 2 mm in length and 1½ to 2 mm in diameter. The canaliculi lie within the eyelid margin and proceed medially for 8 mm and then join, in most cases, the common canaliculus, 3 to 5 mm in length, which empties into the lacrimal sac at the junction of its upper third and lower two-thirds (Fig. 1). The common internal punctum may have folds of tissues surrounding it acting as a valve that may prevent decompression at the lacrimal sac in cases of mucocele or pyocele.
