Fig. 4.1
The lacrimal drainage system has numerous mucosal folds or valves across its length
The Valve of Rosenmüller
The so-called valve of Rosenmüller [4, 5] is situated, although only in a half of cases [6], at the junction between the common canaliculus and the sac [7]. This structure is not a valve, in truth, but only a mucosal fold. A valve-like mechanism here is contributed and functionally structured by movement of the common lacrimal canaliculus in blinking, which originates from contraction and relaxation by Horner’s muscle [8]. The internal canalicular orifice largely opens by a temporal traction of Horner’s muscle during eye closing but moves nasally during an eye opening [8].
The diverticulum, called the sinus of Maier [1, 2], is obvious, especially during eyelid closure, in which folds or membranes are not shown (Figs. 4.2 and 4.3). These folds or membranes only reflect a mucosal spare in the closed state of the internal canalicular orifice, allowing for expansion of the diverticulum. As the lacrimal sac comprises a cavernous structure [9, 10] and may not withstand dynamic movements during repetitive blinking, such a buffering structure may be necessary. Therefore, the movement of the internal canalicular orifice may not directly contribute to lacrimal drainage or antiregurgitation, but protects the sac against repetitive blinking.
Fig. 4.2
A sinus of Maier is shown here, into which the canalicular part is expanded (Elastica van Gieson stain)
Fig. 4.3
A sinus of Maier, in which a part of sac is expanded. The superior and inferior canaliculi separately empty into the sinus of Maier (Masson’s trichrome stain)
Studies for the valve of Rosenmüller have been mostly performed using cadavers. Although cadavers usually have closed eyelids, their Horner’s muscle tone was completely lost [11], which is similar to an eyelid in the opening state with closing of the internal canalicular orifice. This situation may show folds or membranes at the internal canalicular orifice. Cadaveric studies would evaluate only one aspect of the above process. Live patients enable us to observe opening and closing of the internal canalicular orifice. The valve of Rosenmüller may thus be a phantom anatomy.
The Valve of Hasner
The so-called valve of Hasner is only the terminal soft tissue component of the lacrimal excretory passage [12]. An imperforate valve will result in epiphora and signs of congenital nasolacrimal duct obstruction [12]. This soft tissue is situated at the meatal opening of the nasolacrimal duct (NLD), several millimeters inferiorly after NLD’s exit from the bony lacrimal canal [13, 14]. This soft tissue has been thought to prevent air current or fluid from within the nose being drawn up into the lacrimal duct.
The shape of this terminal soft tissue shows four types: wide-open type (12 %), valve-like type (8 %), sleeve-like type (14 %), and adhesive type (66 %) [14]. Judging from these variations, the wide open type at least should demonstrate regurgitation of air current or fluid [12]. Bert (quoted by Aubaret) [1, 2] found that colored fluids injected in the nose escaped from the lacrimal puncta only 3 times in 18 experiments, whereas direct injections into the duct invariably appeared at these points, showing that the terminal soft tissue of the lacrimal excretory passage usually shows valve-like mechanism but not always. Although Bert’s study has been reported more than 100 years ago, it has been under surgeons’ recognition.
Anatomy of the Medial Canthal Tendon (MCT)
History of the MCT Anatomy
The medial canthus is a complex anatomical region and the most striking entity here is the medial canthal tendon (MCT) [15–19]. The MCT was earlier known as the “medial canthal ligament” [20]. In view of inadequate information, some considered it to be a ligament, but others saw it simply as a large adhesion to the periosteum of the frontal process of maxilla [20].
A different opinion about the medial canthal region was published in 1970s by Lester T. Jones, who was the first to reconsider this classical anatomy. Jones and his colleague reported that the medial canthal ligament was not a ligament, but rather a tendon of the orbicularis oculi muscle (OOM) [17].
The classical teaching about MCT is its two limbs, i.e., the anterior and posterior [18, 21]. The anterior limb, which is stronger than the posterior limb [22], was thought to be situated in front of the lacrimal sac and connected to the anterior lacrimal crest and the medial aspect of the tarsal plate [18]. Ritleng et al. also stated that the anterior part of the medial canthal ligament was actually the tendon of the pretarsal OOM [3] and suggested to call it as the “medial palpebral tendon” [18]. Yamamoto et al. proposed that the MCT comprised an aggregate of muscle fibers from the orbital area of the OOM, as well as the tendon from the tarsal area [16].
Many anatomists worked on the anatomy of the MCT, however we revisited the anterior limb to include two lamellae, i.e., the anterior and posterior [23]. The anterior lamella is the tendon of the pretarsal part of the OOM [23]. The posterior lamella is the musculotendinous junction of the preseptal and orbital parts of the OOM [23]. The anterior limb continues to the pretarsal OOM without insertion into the tarsal plate [24].
The classical teaching with regards to the posterior limb is its attachment to the posterior lacrimal crest and tarsal plate and Horner’s being related to its posterior surface (Fig. 4.4) [18]. However, true fixation of the nasal aspect of the tarsal plate is performed by Horner’s muscle and the medial rectus capsulopalpebral fascia (mrCPF) [24] and not by the posterior limb of the MCT. Most researchers considered this posterior limb as a relative subsidiary structure, compared with the anterior limb [22, 25, 26], although some thought the posterior limb to have the same tough fibrous consistency as the anterior limb [27].
Fig. 4.4
Important bony landmarks in medial canthal anatomy
The Truth of the Posterior Limb of the MCT
The classical anatomical teaching has been that the medial canthus is supported by the anterior and posterior limbs of the MCT and the Horner’s muscle. The posterior limb of the medial canthal ligament, as a deep or reflected part arising from the main ligament [18, 25], was thought to be merely a thin fascial expansion [28] or simply a thin and weak structure to assist the anterior limb [26]. The posterior limb of the MCT was thought to be attached behind the lacrimal sac and contiguous with the lacrimal fascia, and thus helped to support the upper part of the lacrimal sac [25].
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
