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Purpose To determine the narrowest diameter of the bony nasolacrimal canal. Methods Fifty-eight bony nasolacrimal canals from 29 Japanese cadavers (12 men and 17 women; average age at death, 83.4 years; range, 70-99 years) had been fixed in 10% buffered formalin before use. After exposing the medial (44 canals) or posterior half (14 canals) of the bony nasolacrimal canal, the part with the shortest anteroposterior or transverse diameter was determined on inspection. These positions from the canal entrance were measured, and the distance ratio, indicating where the shortest diameter was located in relation to the total length of the canal, was calculated. Results The shortest anteroposterior and transverse diameters were at the entrance to the canal in 32 of 44 canals (72.7%) and in 9 of 14 canals (64.3%), respectively. In the other canals, the shortest anteroposterior and transverse diameters were located at an average of 3.6 and 5.6 mm from the entrance, and the distance ratios were 29.0% and 46.7%, respectively. The mean shortest anteroposterior and transverse diameters were 5.6 and 5.6 mm, respectively. Conclusions The shortest anteroposterior and transverse diameters were at the entrance of the canal in most of the bony nasolacrimal canals. These results are comparable with the rate of obstruction at the canal entrance in primary acquired nasolacrimal duct obstruction.

PURPOSE To examine the relative positions of the lacrimal fossa (LF) and the bony nasolacrimal canal (BNLC) in relation to each other and a reference plane. METHODS Forty-two orbits and BNLCs from 21 Asian cadavers (9 men and 12 women; average age at death, 84.4 years; range, 70-99 years) had been fixed in 10% buffered formalin before use. After exposing the LF and the medial half of the BNLC, the authors measured the angles of the longitudinal axis of the LF and the BNLC relative to the aesthetic horizontal plane respectively. Based on these values, the relative orientation of the LF and the BNLC was determined and defined in terms of Δ BNLC-LF. A positive Δ BNLC-LF represents a nasolacrimal canal that descends posteriorly relative to the LF. RESULTS The mean LF, BNLC, and Δ BNLC-LF were 9.5°, 19.8°, and 10.3°, respectively. In 39 passages (92.9%), the Δ BNLC-LF was positive, representing a nasolacrimal canal that is more posteriorly oriented than the LF. In 3 passages (7.1%), the Δ BNLC-LF was equal to or less than 0°; 2 of them (4.8%) had a straight course and 1 passage (2.4%) had a negative value. CONCLUSIONS In most patients, the BNLC is directed more posteriorly than the LF. This finding may help in preventing an inadvertent false passage during probing and intubation in patients with epiphora.

PURPOSE To clarify the causative factor of Asian double eyelid. DESIGN Experimental anatomic study. PARTICIPANTS Twenty-six upper eyelids (13 right and 13 left) from 17 Japanese cadavers (9 males and 8 females, mean age at death: 73.1 years). METHODS The specimens, obtained from the central part of the upper eyelids, were dehydrated, embedded in paraffin, cut into 7-μm thick slices and stained with Masson trichrome. Statistical analysis was based on the Mann-Whitney U test. Statistical significance was defined as p < 0.05. MAIN OUTCOME MEASURES Orbicularis oculi muscle thickness and shape, with or without the levator extension, orbicularis oculi muscle bundle spacing, thickness of upper eyelid skin and subcutaneous tissue, fusional site between the levator aponeurosis and the orbital septum, with or without inferior drooping of fat tissue. RESULTS The orbicularis muscle was thinner at the skin crease of a double eyelid than at 10 mm from the eyelid margin in the single eyelid group (p = 0.029). In 3 specimens the skin crease of double eyelid was at the tip of the bending orbicularis muscle, which was thick. Although the skin crease in the region of a double eyelid was thinner than in other parts of the skin, excluding the simple crease regions, other outcome measures were not shown as definite causative factors in creating the Asian double eyelid. CONCLUSIONS The thickness of orbicularis oculi muscle or its bending shape, and the thickness of the skin at the skin crease, are major causative factors in Asian double eyelid formation.

PURPOSE This study was designed to examine the anatomical relationship between Horner's muscle and the lacrimal sac at 3 representative levels of the lacrimal sac and to verify the contribution of Horner's muscle to lacrimal sac drainage. METHODS Seven ocular specimens from 7 elderly Japanese cadavers, fixed in 10% buffered formalin, were analyzed. Axial sections were made parallel to the eyelid margin at 1 mm above the upper eyelid margin, 1 mm below the lower eyelid margin, and 3 mm below the lower eyelid margin. The vertical common fascial length, length of the lateral lacrimal sac wall, and the proportion between the 2 were measured for each specimen at the 3 levels. RESULTS The vertical common fascial length and its proportion to the length of the lateral lacrimal sac wall were statistically the same at all 3 levels of the lacrimal sac. CONCLUSIONS Based on the present anatomical findings, the activity of Horner's muscle may be the same for all sac levels, although this hypothesis should be examined by further experimental research, such as manometric studies of the sac at different levels along its length.

Purpose To examine the junctional variations of the levator palpebrae superioris (LPS) muscle, the levator aponeurosis, and Muller muscle in Asians. Methods Postmortem specimens of 17 upper eyelids and orbits of 13 Asians (9 right and 8 left; average age, 78.5 years old) were used. Full-thickness sagittal sections of the central part of the upper eyelids and orbits were microscopically examined using Masson trichrome staining. Results Peripheral branching of the LPS muscle was demonstrated in 12 specimens. Five of these showed that the complete origin of Muller muscle was from the inferior branch, whereas the levator aponeurosis originated from the superior branch. In the other 7 specimens, part of the Muller muscle origin was from the orbital smooth muscle network. The superior branch was significantly thicker (average: 340.8 μm) than the inferior branch (average: 247.5 μm) (p = 0.014). Two specimens did not demonstrate any branching structures, and most areas of the distal end of the LPS muscle was connected to Muller muscle. The other 3 specimens also did not demonstrate these branching structures, and Muller muscle was seen originating from the orbital smooth muscle network and from the inferior aspect of the LPS muscle. Conclusions The authors demonstrated variations of the junctional anatomy of the LPS muscle, the levator aponeurosis, and Muller muscle. These new anatomical findings may help better understanding of the anatomy of the upper eyelid and the relations to the orbital smooth muscle network.

PURPOSE To examine the anatomical relationships of the anterior ethmoidal foramen (AEF), medial canthal tendon (MCT), and lacrimal fossa (LF) in Japanese individuals. METHODS Thirty-eight orbits from 19 Japanese cadavers (7 men and 12 women; average age at death, 89.3 years) were used in this experimental anatomical study. The AEF, MCT, and superior border of the LF were exposed. The following distances were then measured: 1) from the point at the medial orbital rim directly anterior to the AEF to the superior border of the MCT (AEF-MCT), and 2) from the superior border of the LF to the superior border of the MCT (LF-MCT). RESULTS (AEF-MCT) and (LF-MCT) distances were 9.40±1.92 (mean±standard deviation) and 4.21±1.18 mm, respectively. No values of (LF-MCT) exceeded the mean (AEF-MCT) (9.40 mm). CONCLUSIONS The transcutaneous anterior ethmoidal nerve block can be reliably performed without injury to the lacrimal sac by inserting a needle approximately 9 mm superior to the superior border of the MCT.

Purpose: To identify microscopically lateral tarsal fixation in Asians. Methods: Specimens from 19 postmortem lateral eyelids and orbits of 11 Asians (11 right, 8 left; aged 45–96 years at death) were used. Samples damaged on sectioning and samples without tarsal plates were excluded. The samples were fixed in 10% buffered formalin and examined under a microscope. Two levels of tarsus were observed in the upper and lower eyelids, suggesting the possibility of different means of fixation. The first and second sections, which were incised parallel to the eyelid margin, were obtained at 1 mm and 5 mm from the upper eyelid margin, and at 1 mm and 3 mm from the lower eyelid margin. The sections were stained with Masson trichrome. Results: The first sections of all upper eyelids and those of the lower eyelids except one showed tarsal fixation by both the lateral rectus capsulopalpebral fascia (lr-CPF) and the tendon-ligament complex of the lateral canthal tendon (LCT), which in several cases received the muscle of Riolan. The second sections of all upper eyelids showed fixation by the lr-CPF and the ligamentous part of the LCT. The second sections of the lower eyelids were mostly similar to the second sections of upper eyelids, though some showed only ligamentous fixation. The lr-CPF in all cases included a small amount of smooth muscle fibers. Conclusions: The lateral aspect of the tarsus is supported by the lr-CPF and the LCT, which in some cases includes the muscle of Riolan.

PURPOSE To investigate the two-fold structure of the levator aponeurosis, which is partly composed of independent smooth muscles. MATERIALS AND METHODS Fifteen upper eyelids of 12 Asian postmortems, with age at death ranging from 72 to 91 years, were examined. In 9 eyelids, posterior lamella tissue of the upper eyelid was removed to observe the stratified structures of the levator aponeurosis. Six full-thickness eyelids were used to observe the attachment site or the continuity between the levator aponeurosis and its surrounding tissues. The eyelids were incised perpendicularly in the center of the eyelid; samples were stained with Masson trichrome and antismooth muscle actin antibody and examined microscopically. RESULTS Masson trichrome staining demonstrated the two-layered nature of the levator aponeurosis. The anterior layer was characterized by thick, robust fibrous tissue, and the posterior by thinner fibrous tissue. Although both layers contained muscle structures, the posterior layer contained more than the anterior. Immunostaining with antismooth muscle actin antibody revealed that the muscle in both layers was smooth muscle. The anterior layer continued to the orbital septum and the submuscular fibroadipose tissue; the posterior layers, located in front of Muller muscle and its tendon, attached to the anterior inferior one-third of the tarsus. Part of the anterior layer went through the orbicularis oculi muscle and attached to the subcuticular tissue. CONCLUSIONS The levator aponeurosis is stratified, consisting of two layers than contain smooth muscle components in their proximal portions. It pulls mainly the preaponeurotic fat and anterior eyelid lamella. This partially regulates the tension of the eyelid and contributes to the ordered movement of the upper eyelid.

Purpose This study was designed to examine the distance from the posterior lacrimal crest to the posterior margin of the Horner's muscle origin (the PLC-HMO distance), considering their complex anatomical relationship. Methods Eight macroscopic specimens from 8 Japanese cadavers and 7 microscopic specimens from 7 Japanese cadavers, fixed in 10% buffered formalin, were analyzed. Macroscopically, the PLC-HMO distance was measured at 2 mm superior to the most posterior point of the muscle origin (Group A), directly at the most posterior point (Group B) and 2 mm inferior to the most posterior point (Group C). Microscopically, the PLC-HMO distance was measured in axial sections at 1 mm above the upper eyelid margin (Group 1), 1 mm below the lower eyelid margin (Group 2), and 3 mm below the lower eyelid margin (Group 3). Results In the macroscopic study, the average PLC-HMO distance was 2.94, 2.57, and 2.05 mm for Groups A, B and C, respectively. The distance for Group C was significantly smaller than that of Group A (p = 0.006). In the microscopic study, the average PLC-HMO distance was 3.62, 3.74, and 3.14 mm for Groups 1, 2 and 3, respectively (no significant difference). Conclusions The PLC-HMO distance was approximately 2-4 mm with some specimens showing a smaller distance inferiorly.

Purpose To examine the positional relationship between the ethmoidal foramina and the frontoethmoidal suture. Methods Eighty-four orbits of 42 Japanese cadavers (24 male and 18 female cadavers; average age at death, 81.0 years; range, 61-101 years), fixed in 10% buffered formalin, were used for investigation. The most anterior or posterior ethmoidal foramen was defined as the anterior or posterior ethmoidal foramen, respectively. All the intermediate foramina were determined as the accessory foramina. The vertical distances from the frontoethmoidal suture to the anterior, posterior, and accessory ethmoidal foramina were examined. Results Seventeen anterior ethmoidal foramina (20.2%) were situated above the frontoethmoidal suture (mean distance, 1.8 mm), and 2 posterior ethmoidal foramina (2.3%) were situated at 1.0 mm and 1.5 mm above the suture. Although accessory ethmoidal foramina were detected in 32 orbits (38.1%), one accessory foramen (middle ethmoidal foramen) was identified in 30 orbits, and 2 foramina (additional deep-middle ethmoidal foramina), in 2 orbits. One middle ethmoidal foramen (3.1%) and 1 deep-middle ethmoidal foramen (50.0%) were located at 1.5 mm above the suture. In total, 2 of the 34 accessory ethmoidal foramina (5.9%) exhibited the extrasutural location. Conclusions Several ethmoidal foramina were situated above the frontoethmoidal suture. The anterior ethmoidal foramen most frequently showed the situation, followed by the accessory and posterior foramina, in order. Our findings help predict the anatomical variations in the location of the ethmoidal foramina in relation to the frontoethmoidal suture, thereby enhancing safety for medial orbital wall surgery.

PURPOSE To characterize the macroscopic anatomy of the vertical lacrimal canaliculus and the lacrimal punctum in relation to the tarsal plate. METHODS Twenty-eight eyelids of 7 cadavers (mean age at death, 79.1 years; range, 65-93 years) were used for the investigation. The harvested eyelids were incised vertically around the central part of the upper and lower eyelids. The whole superior border of the upper tarsal plate and the whole inferior border of the lower tarsal plate were exposed by removing the soft tissues adjacent to them. We first examined whether these tarsal plates contained a lacrimal punctum. If the lacrimal punctum was found, we inserted a lacrimal probe to the punctum and measured the length covered by the tarsal plate using a millimeter ruler. RESULTS All the tarsal plates contained the lacrimal punctum, and the mean length of the canaliculi covered by the tarsal plates was 2.82 mm (range, 2.3-3.0 mm) in the upper eyelid and 2.39 mm (range, 2.3-2.5 mm) in the lower eyelid. CONCLUSIONS Since the length of the vertical lacrimal canaliculus including the lacrimal punctum is generally 2 mm, they are considered as tarsal components in both the upper and lower eyelids.

Purpose To analyze the distribution and characteristics of upper eyelid skin elastic fibers in different areas of skin thickness and in relation to the eyelid crease. Methods We used 12 postmortem eyelids (6 right, 6 left) of 10 Asian cadavers (mean age: 77.1 years at death), fixed in 10% buffered formalin. Full-thickness sagittal sections of the upper eyelids were dehydrated, embedded in paraffin, and cut in 7-μm-thick sections. The sliced sections were stained with elastica van Gieson. Results The upper eyelid skin was divided in 2 areas; the thinner and thicker areas. The average distance from the eyelid margin to the border between the 2 areas was 17.8 mm (range, 12.8-24.0 mm). Ten eyelids showed a small amount of elastic fibers in the thinner skin area, and 2 eyelids were rich in elastic fibers in the same area. The volume of elastic fibers multiplied in the thicker skin area. The elastic fibers in the eyelid margin area were fine and nonfragmented, whereas in other areas they were thicker and more fragmented. A part below the skin creases showed the same concentration of elastic fibers to other areas of the upper eyelid skin. Conclusions Most upper eyelids demonstrated a small amount of elastic fibers in the thinner skin area and a larger amount in the thicker area. The eyelid margin elastic fibers had a normal morphology, whereas in other areas they were more disintegrated, thicker, and fragmented. The eyelid creases and the elastic fiber concentration were unrelated.

Purpose To describe the anatomic characteristics of Muller's muscle tendon. Materials and methods Twelve postmortem, buffered formalin (10%)-fixed eyelids (6 right, 6 left) of 10 Asians (aged 62 to 92 years at death; mean age: 77.1 years) were used. Full-thickness sagittal sections of the upper eyelid specimens were dehydrated and embedded in paraffin and cut in 7-μm-thickness sagittal sections. Sliced sections were stained with elastica van Gieson. The concentration of the elastic fibers in Muller's muscle tendon was analyzed and compared with the concentration in the levator aponeurosis. Fat deposition and the dimensions of Muller's muscle tendon were also analyzed. Results Both Muller's muscle tendon and the levator aponeurosis contained elastic fibers, which were more abundant in Muller's muscle tendon. Fat deposition in Muller's muscle tendon was demonstrated only in one specimen from an 84-year-old male. The average length of Muller's muscle tendon was 2.56 mm (range: 1.40-5.64 mm), and the average thickness of the tendon was 0.27 mm (range: 0.08-0.88 mm). There was no correlation between cadaver age and muscle length or thickness. Conclusions Muller's muscle tendon is rich in elastic fibers with minimal age-related fat deposition.

A detailed understanding of the relationship between the ethmoidal sinus and the intracranial cavity is essential to prevent intracranial penetration during orbital surgery. The authors analyzed 10 postmortem orbits with their adjacent skull bases of 5 Asian cadavers (3 males and 2 females; mean age of 80 years at death). After removing all orbital contents, skull and brain, the medial orbital wall, ethmoidal cells, and ethmoidal roof were also removed. From the intracranial cavity view, the ethmoidal roof was situated just lateral to the cribriform plate. From the orbital view, the location of the roof was close to the superior border of the medial orbital wall. These anatomical observations may be useful to prevent intracranial penetration and cerebrospinal fluid leakage during medial orbital wall decompression.

Purpose To examine gender differences in bony nasolacrimal canal entrance diameters in cadavers. Methods Fifty-seven orbits from 29 Japanese cadavers (37 orbits from 19 men and 20 orbits from 10 women), aged 61 to 96 years at death (mean: 79.5 years; men: 77.8 years; women: 82.7 years), were fixed in 10% buffered formalin. The anteroposterior and transverse diameters of the bony nasolacrimal canal entrance were measured. The diameters were compared between genders using Student's t test. Results The mean anteroposterior diameters in all subjects, men, and women, were 6.9, 6.8, and 7.2 mm, and the equivalent transverse diameters were 5.7, 6.1, and 5.0 mm, respectively. There was no significant gender difference in the anteroposterior diameter (p = 0.287), but the transverse diameter was significantly shorter in women than in men (p = 0.004). Conclusions The transverse diameter of the bony nasolacrimal canal entrance was significantly shorter in women than in men, which may be a possible factor contributing to the higher incidence of primary acquired nasolacrimal duct obstruction in women.