The lower-positioned transverse ligament (LPTL) is one of the main supporting structures of the upper eyelids [1Kakizaki H, Zako M, Miyaishi O, et al. Posterior aspect of the orbital septum is reinforced by ligaments Jpn J Ophthalmol 2005; 49: 477-80.,2Kakizaki H, Zako M, Nakano T, et al. Modified course of the lower-positioned transverse ligament Br J Plast Surg 2005; 58: 1035-6.], and usually exists in puffy upper eyelids [3Yuzuriha S, Matsuo K, Kushima H. An anatomical structure, which results in puffiness of the upper eyelid and a narrow palpebral fissure in the Mongoloid eye Br J Plast Surg 2000; 53: 466-72.]. Since the LPTL regulates upper eyelid height [3Yuzuriha S, Matsuo K, Kushima H. An anatomical structure, which results in puffiness of the upper eyelid and a narrow palpebral fissure in the Mongoloid eye Br J Plast Surg 2000; 53: 466-72.], when a thick LPTL occurs as in blepharoplasty or blepharoptosis surgery, incision of the LPTL is recommended to secure appropriate upper eyelid height [3Yuzuriha S, Matsuo K, Kushima H. An anatomical structure, which results in puffiness of the upper eyelid and a narrow palpebral fissure in the Mongoloid eye Br J Plast Surg 2000; 53: 466-72.].

The LPTL was believed to be positioned around the lateral horn of the levator aponeurosis, and to run in parallel with a junction between the orbital septum and the levator aponeurosis (junction) [3Yuzuriha S, Matsuo K, Kushima H. An anatomical structure, which results in puffiness of the upper eyelid and a narrow palpebral fissure in the Mongoloid eye Br J Plast Surg 2000; 53: 466-72.]. However, some different anatomical findings on the LPTL have been reported [1Kakizaki H, Zako M, Miyaishi O, et al. Posterior aspect of the orbital septum is reinforced by ligaments Jpn J Ophthalmol 2005; 49: 477-80.,2Kakizaki H, Zako M, Nakano T, et al. Modified course of the lower-positioned transverse ligament Br J Plast Surg 2005; 58: 1035-6.]. The LPTL was shown to originate from the trochlea, run inferolaterally and to pass the junction, where it reflected the posterior aspect of the orbital septum, and finally to reach the lateral orbital rim (Fig. 1). That is, the true LPTL differs from the tissue running parallel to the junction.

Fig. (1) Modified course of the lower-positioned transverse ligament (LPTL) (top: superior; left: medial). Reprinted with permission of the Japanese Journal of Ophthalmology (Kakizaki H, et al. Posterior aspect of the orbital septum is reinforced by ligaments. Jpn J Ophthalmol 2005; 49: 477-80). The LPTL originates from the trochlea and runs in an inferolateral direction. The LPTL passes over the junction between the orbital septum and levator aponeurosis, attaches onto the posterior aspect of the orbital septum, and runs towards the lateral orbital rim. The LPTL was harvested in the part that the arrow indicates. Tr, trochlea; Jun, junction of the orbital septum and the levator aponeurosis; LA, levator aponeurosis; LG, lacrimal gland; MTL, medial horn tensing ligament; OS, orbital septum; Lig, ligaments on the posterior aspect of the orbital septum; PO, periosteum.

Fig. (2) Light microscopic findings. (A) Lower-positioned transverse ligament. Collagen bundles are scattered and thin. (B) The parallel tissue on the junction between the orbital septum and the levator aponeurosis. Thick collagen bundles with a few elastic fibres congregate.

Fig. (3) Transmission electron microscopic findings. (A) Lower-positioned transverse ligament. (B) The parallel tissue on the junction between the orbital septum and the aponeurosis. Both tissues contain microfibrils with the same periodicity and thickness.

From histological findings, the LPTL was thought to contain tighter collagen bundles than the Whitnall ligament [3Yuzuriha S, Matsuo K, Kushima H. An anatomical structure, which results in puffiness of the upper eyelid and a narrow palpebral fissure in the Mongoloid eye Br J Plast Surg 2000; 53: 466-72.]. However, since the above noted histological results were obtained before elucidation of the precise course of the LPTL, it was uncertain whether the true LPTL was adequately harvested. As well, the LPTL has not been examined using transmission electron microscopy.

In the present study, we histologically examined the LPTL and the tissue running parallel to the junction using light and transmission electron microscopy.

Ten upper eyelids of 6 Asian patients (5 females and 1 male, average age 61.8 years old, range, 41-75), who underwent blepharoptosis repairs, were examined. Eight eyelids showed involutional blepharoptoses, and 2 blepharoptoses after cataract surgery. Patients with preceding traumas and/or past eyelid surgeries were excluded. All patients were informed of the study, and proper consent and approval were obtained preoperatively. All methods for securing human tissue were humane and complied with the tenets of the Declaration of Helsinki.

In blepharoptosis repairs, at first, the anterior surface of the tarsus was exposed. Dissection under the orbicularis oculi muscle was advanced superiorly to expose the junction. The orbital septum was transversely incised above the junction, because the transverse septal incision just on the junction sometimes complicates detection of the LPTL. Then, dissection was extended superomedially to confirm the course of the LPTL, which running on the aponeurosis was also confirmed to distinguish it from the Whitnall ligament [4Anderson RL, Dixon RS. The role of Whitnall's ligament in ptosis surgery Arch Ophthalmol 1979; 97: 705-.,5Ettl A, Zonneveld F, Daxer A, Koornneef L. Is Whitnall's ligament responsible for the curved course of the levator palpebral superioris muscle? Ophthalmic Res 1998; 30: 321-6.]. We then harvested the LPTL in a part that ran inferolaterally immediately before crossing the junction. We also harvested the parallel tissue on the junction in the lower part in which the LPTL was harvested. Each of the tissues was divided into 2 parts; one was fixed in 10% buffered formalin and the other in 2% glutaraldehyde. Tissue sections of the formalin-fixed specimen were stained with Elastica van Gieson [6], which were also used in a former study [3Yuzuriha S, Matsuo K, Kushima H. An anatomical structure, which results in puffiness of the upper eyelid and a narrow palpebral fissure in the Mongoloid eye Br J Plast Surg 2000; 53: 466-72.], and examined light-microscopically (BX-40, OLYMPUS, Tokyo, Japan). The histological results we obtained were compared with those histological results presented earlier [3Yuzuriha S, Matsuo K, Kushima H. An anatomical structure, which results in puffiness of the upper eyelid and a narrow palpebral fissure in the Mongoloid eye Br J Plast Surg 2000; 53: 466-72.]. As well, ultra-slice sections fixed in glutaraldehyde were stained with lead and uranyl acetate and were examined with a transmission electron microscope (JEM-1200EX||, JEOL, Tokyo, Japan).

Light-microscopically, the LPTL in all cases contained looser and thinner collagen bundles with less elastic fibres than the tissue running parallel to the junction (Fig. 2A). The LPTL was histologically analogous to the previously reported Whitnall ligament [3Yuzuriha S, Matsuo K, Kushima H. An anatomical structure, which results in puffiness of the upper eyelid and a narrow palpebral fissure in the Mongoloid eye Br J Plast Surg 2000; 53: 466-72.], while the tissue on the junction (Fig. 2B) was analogous to the previously reported LPTL [3Yuzuriha S, Matsuo K, Kushima H. An anatomical structure, which results in puffiness of the upper eyelid and a narrow palpebral fissure in the Mongoloid eye Br J Plast Surg 2000; 53: 466-72.]. Electron microscopic findings showed that collagen microfibrils of the LPTL (Fig. 3A) had almost the same periodicity and thickness as those in the parallel tissue on the junction (Fig. 3B).

The LPTL showed a different light-microscopic composition to that of the tissue running parallel to the junction, although both tissue architectures could not be distinguished electron microscopically, indicating that the strength of each tissue was different. Each tissue could have specific physiological functions depending on their anatomical position. Since the LPTL contains looser and thinner collagen bundles and less elastic fibres than the parallel tissue, the strength loaded onto the LPTL might be less than that on the parallel tissue. Thus, most upper eyelids, except ones with a very robust LPTL [2Kakizaki H, Zako M, Nakano T, et al. Modified course of the lower-positioned transverse ligament Br J Plast Surg 2005; 58: 1035-6.,3Yuzuriha S, Matsuo K, Kushima H. An anatomical structure, which results in puffiness of the upper eyelid and a narrow palpebral fissure in the Mongoloid eye Br J Plast Surg 2000; 53: 466-72.], can move appropriately without restriction by the LPTL. Also, the tighter and thicker composition of the parallel tissue is reasonably suitable for repetitional eye blinking because the junction provides a pivotal position to lift the preaponeurotic fat pad [7Kakizaki H, Zako M, Nakano T, et al. The levator aponeurosis consists of two layers that include smooth muscle Ophthal Plast Reconstr Surg 2005; 21: 281-4.].

The LPTL reinforces the orbital septum, with which it sustains a preaponeurotic fat pad [1Kakizaki H, Zako M, Miyaishi O, et al. Posterior aspect of the orbital septum is reinforced by ligaments Jpn J Ophthalmol 2005; 49: 477-80.]. Especially in Asians, a supporting structure is necessary for the orbital septum because preaponeurotic fat tends to drop inferiorly and project anteriorly due to puffiness. This is why the LPTL is a desirable structure to support the preaponeurotic fat pad. However, the smaller elasticity of the LPTL sometimes causes a problem in which the extension of the levator aponeurosis is disturbed. Ordinary thin collagen bundles of the LPTL may be an adaptation to compensate for this drawback. Since the LPTL runs obliquely [1Kakizaki H, Zako M, Miyaishi O, et al. Posterior aspect of the orbital septum is reinforced by ligaments Jpn J Ophthalmol 2005; 49: 477-80.], roughly coinciding with the direction of blinking, the LPTL needs to be incised in cases with insufficient eyelid closure in blepharoptosis repairs.

The LPTL shares some common macroscopic features with Whitnall ligament [8Kakizaki H, Zako M, Nakano T, et al. Anatomical study of the lower-positioned transverse ligament Br J Plast Surg 2004; 57: 370-2.], indicating that both structures may have derived from the same origin [8Kakizaki H, Zako M, Nakano T, et al. Anatomical study of the lower-positioned transverse ligament Br J Plast Surg 2004; 57: 370-2.,9Hwang K, Kim DJ, Chung RS, Lee SI, Hiraga Y, et al. An anatomical study of the junction of the orbital septum and the levator aponeurosis in Orientals Br J Plast Surg 1998; 51: 594-8.]. Although the present study did not histologically examine the Whitnall ligament, compared to light-microscopic findings of the Whitnall ligament [3Yuzuriha S, Matsuo K, Kushima H. An anatomical structure, which results in puffiness of the upper eyelid and a narrow palpebral fissure in the Mongoloid eye Br J Plast Surg 2000; 53: 466-72.], the LPTL showed histological similarities. In this, the present study largely supports the hypothesis that both ligaments share the same origin.

The LPTL is a loose and inelastic structure, which is a different structure from that of the tissue running parallel to the junction, but showed similarities to the Whitnall ligament. Although there may be some limitations in the present study in terms of blepharoptoses and age-related degenerative changes, we believe that the results here will help towards a precise understanding of the anatomy of the upper eyelid.