Two Types of the Sinus of Maier: An Anatomic Study

Purpose: To show the morphological characteristics of two different types of the sinus of Maier, one with a lacrimal sac diverticulum supplied by separate canalicular openings, and the other with a terminal dilatation of the common lacrimal canaliculus. Methods: Twelve coronal specimens (6 right and 6 left) from 6 Japanese cadavers (age range, 70-90 years at death) and 15 axial specimens of 11 Japanese cadavers (8 right, 7 left; age range, 45-89 years at death), fixed in 10% buffered formalin, were used. All specimens were stained with Masson's trichrome. Results: The sinus of Maier, with a lacrimal sac diverticulum supplied by separate canalicular openings, was shown in one coronally sectioned group, with a diameter of 1.29mm. The mucosa between both openings (0.282mm length) comprised stratified squamous epithelia, which was characteristic of the lacrimal canaliculi. The diverticular mucosa was lined by a stratified columnar epithelium, which corresponded to the lacrimal sac. The sinus of Maier, with a terminal dilatation of the common lacrimal canaliculus and with a diameter of 0.51mm, was demonstrated in one axially sectioned group. Conclusions: The morphological characteristics of two types of the sinus of Maier were described in this study. One type was the lacrimal sac diverticulum supplied by separate canalicular openings, and the other was the terminal dilatation of the common lacrimal canaliculus.