Nasolacrimal duct opening to the inferior nasal meatus in human fetuses.

The purpose of this study is to describe the Hasner's membrane which is the main factor of congenital nasolacrimal duct obstruction. Hasner's membrane at the nasal end of the fetal nasolacrimal duct (NLD) is considered to rupture at and after birth. However, topographical anatomy around the membrane as well as a mechanism of rupture seems to be still obscure. We observed frontal or sagittal sections of 20 late-stage fetuses (28-33 weeks) and found the on-going rupture in 2 specimens. The present sections demonstrated that 1) the nasal dilation was not a simple ball-like structure but extended posteriorly and laterally; 2) dilation of the NLD consistently involved the lacrimal sac; 3) Hasner's membrane and ductal mucosal layer contained no macrophages and no or few arteries and nerves. The posterior extension of the NLD end ranged from 1-2 mm, while the lateral extension 3-5 mm although a site of the thinnest membrane varied in location between specimens. Moreover, the thickest NLD due to dilation was in the slightly orbital or upper side of the nasal end. Therefore, before surgical treatment of Hasner's membrane, evaluation using medical images seems to be necessary. Since the nasal epithelium on Hasner's membrane was most likely to destroy earlier than the NLD mucosal lining, observations of the membrane from the nasal cavity seemed helpful for diagnosis at which site would be broken and when.

Early fetal development of the medial canthal ligament and Horner’s muscle: a histological study

Horner's muscle is a well known structure that accelerates lacrimal drainage. However, the fetal topographical relationship between this muscle and the medial canthal ligament (MCL) seems to differ from the adult morphology because a fetal connective tissue band toward the eyelids has never been demonstrated.We examined horizontal and frontal sections of 15 specimens (20-30 weeks of gestation) from the large collection of human fetuses stored at the Complutense University in Madrid (Spain). Frontal sections demonstrated the orbicularis oculi muscle inserting to a raphe-like structure along the horizontal parts of the lacrimal canaliculi. In horizontal sections, the raphe-like structure corresponded to a fibrous tissue mass sandwiched by the superior and inferior lacrimal canaliculi. The tendons of Horner's muscle were divided into 1) the so-called "reflection tendon" that included the typical myotendineous junction at the insertion into the maxilla, and 2) the so-called "direct tendon" in the roof of the lacrimal sac. However, Horner's muscle did not insert into the canaliculi, but was simply attached to, or embedded in, the fibrous sheath around them. Notably, none of these connective tissue structures was attached to the tarsi. Horner's muscle and its tendon might contribute to formation of the bony attachment of the future MCL, but the main part of the MCL most likely originates from the raphe-like structure. The connection between the MCL and the tarsi seems to be established after birth due to the growth of connective tissue along the lacrimal canaliculi. Although congenital entropion is a rare condition among Westerners, the present study demonstrated that the tarsus is unlikely to be fixed at a late stage in Western fetuses (AU)

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Fetal check ligament connected between the conjunctiva and the medial and lateral recti.

PURPOSE: There seems to be little or no information about the morphology of the fetal eye check ligament. METHODS: The authors examined longitudinal and cross-histologic sections from the large collection of human fetuses at Universidad Complutense, Madrid. RESULTS: In longitudinal sections from 20 fetuses (four at each of 12, 15, 20, 25, and 30 weeks of gestation), a distinct connective tissue band was found connecting the medial and lateral recti and the limbus of the conjunctiva (sites at and around the lateral and medial angles of the conjunctival space). Silver impregnation revealed that the muscle endomysium (type 4 collagen dominant) was connected with composite fibers of the band (type 1 collagen). The cross-sections from three fetuses (20 weeks) exhibited a site-dependent difference in the rectus sheaths: the orbital-sided sheath suddenly increased in thickness when it tightly attached to the muscle bundles. The attaching orbital-sided muscle bundles reached 14% to 15% (or 18%-20%) in the cross-sectional area of the MR (or the LR). CONCLUSIONS: Taken together, the distinct connective tissue band extending to the conjunctiva was "originated from" the MR and LR rather than from a part of the muscles inserting into the connective tissue band. This band was most likely a primitive form of the check ligament. The authors hypothesize that the primitive check ligament conducts muscle tension to the conjunctiva to coordinate growth patterns between the anterior and posterior sides of the eyeball. This hypothesis may support en bloc recession for infantile esotropia.

Human orbital muscle: a new point of view from the fetal development of extraocular connective tissues.

PURPOSE: In the human body, the orbital muscle is a limited smooth-muscle tissue extending between hard tissues. To provide better understanding of its function, the authors re-examined its development in fetuses. METHODS: Using 20 human fetuses (12-25 weeks of gestation), semiserial horizontal or sagittal paraffin sections were prepared at intervals of 20 to 100 µm. In addition to routine histology, the authors performed silver staining as well as immunohistochemistry for alpha smooth-muscle actin (SMA), vimentin, S100 protein, and tyrosine hydroxylase. RESULTS: Up to 12 weeks, the orbital muscle appeared as a plate-like mesenchymal condensation between the ciliary and sphenopalatine ganglia. Up to 15 weeks, the thick smooth-muscle layer provided an inferoposterior wall for the orbit. A notable feature was a difference in fatty tissue development between the ocular (anterior) and posterior sides of the orbital muscle. At 20 and 25 weeks, SMA immunoreactivity and the amount of smooth-muscle basal lamina were decreased, in contrast to an increase in the number of collagenous fiber bundles. Nerves for the orbital muscle are unlikely to contain sympathetic fibers until 15 weeks. CONCLUSIONS: The authors hypothesize that, in the early stage, the orbital muscle separates the orbital content from the surrounding loose spaces to maintain conditions adequate for the development of orbital fat and other connective tissues. Later, the orbital muscle is replaced by collagenous fibers and seems to provide guidance for calcification of the inferoposterior bony orbital wall. Vimentin-positive osteoprogenitor cells appear to migrate from the perichondrium of the sphenoid and ethmoid.

Histotopographical study of human periocular elastic fibers using aldehyde-fuchsin staining with special reference to the sleeve and pulley system for extraocular rectus muscles.

The aim of this study was to investigate the detailed configuration of periocular elastic fibers. Semiserial paraffin sections were made using 40 whole orbital contents from 27 elderly cadavers and stained by the aldehyde-fuchsin method. Periocular tissues were classified into three types according to directions of the elastic fibers, i.e., tissues containing anteroposteriorly running elastic fibers, those with mediolateral fibers, and those with meshwork of fibers. Anteroposterior elastic fiber-dominant tissue was seen in the upper eyelid and newly defined pulley plate for the medial and lateral recti (MR, LR). Mediolateral fibers were predominant in the central part of the inferior rectus pulley. In the pulley plates for the MR and LR, anteroposteriorly running fibers encased the striated muscle. Tenon's capsule and the epimysium of the recti were mediolateral fiber-dominant. However, at the entrance of the muscle terminal where Tenon's capsule reflects and continues to the epimysium, composite elastic fibers provided a meshwork-like skeleton. The elastic mesh was also seen around the lacrimal canaliculi. The pulley for the recti seemed to be composed of two parts--a connective tissue plate encasing the recti and specialized Tenon's capsule at an entrance or porta of the muscle. For both parts, elastic fibers were major functional components. The anteroposterior elastic fibers in the MR and LR pulley plates, especially, seemed to receive anteroposteriorly directed stress and tension from these striated muscles. The elastic interfaces seemed to prevent any concentration of stress that would interfere with periocular striated muscle functions, including hypothetical active pulleys.

An unusual case of congenital convergent convergent strabismus fixus.

BACKGROUND: Convergent strabismus fixus is classified into congenital and acquired types; however, there are only a few detailed case reports of congenital convergent strabismus fixus. Here, we report a rare case of this condition in which the eyeball was shown by imaging diagnosis to be fixed with a hard cord-like material in the orbit. To our knowledge, there have been no previous reports of congenital convergent strabismus fixus caused by an abnormal cord-like material that was clearly identifiable by imaging. CASE REPORT: The patient was a 16 year old female who visited our department for consultation regarding restoration of normal appearance of her strabismus. She had undergone strabismus surgery at the age of 3 years, but a forced duction test was strongly positive in all directions, and the eyeball was not mobile at the time. The initial surgery performed was a tenotomy of the medial rectus muscle and inferior rectus muscle and resection of the lateral rectus muscle of the right eye. The eye position and eye movement remained unchanged after surgery. At this time, MRI of the orbital region was performed, and an abnormal cord-like material connecting the posterior eyeball to the orbital wall was detected in the orbit. The cord-like material was pulling strongly on the posterior eyeball, congenitally fixing the eye position internally. CONCLUSION: We experienced a rare case in which a hard cord-like material in the orbit congenitally fixed the position of the eyeball. On MRI, the intensity of the cord-like material was clearly different from those of the muscle and nerve tissues. Considering the linearity of the cord-like material and the results of a forced duction test, the cord-like material probably consisted of fairly hard tissue, similar to bone.

A case of a slipped medial rectus muscle after strabismus surgery.

BACKGROUND: A slipped muscle after strabismus surgery is a well known complication, but only a few cases have been reported in the medical literature. Here, we report a case of a slipped medial rectus muscle that occurred after strabismus surgery for esotropia. CASE REPORT: The patient was a 10 year old male with an acquired esotropia of 20 PD at distance. For treatment, 3.5 mm bilateral medial rectus recessions was performed. There were no complications during the procedure. On postoperative day 8, the eye position was orthotropic in primary position, but a right exotropia was observed in left gaze. The boy was frequently observed rubbing his right eye after surgery. The right exotropia increased to 30 PD 2 months after surgery. Limited adduction of the right eye, a large widening of the lid fissure on adduction, and mild exophthalmos were observed. Based on the above findings, a slipped medial rectus was suspected, and a second surgery, advancement of the right medial rectus muscle was performed 2.5 months after the initial procedure. After this second procedure, the eyes became orthotropic, and the adduction disorder, large widening the lid fissure, and mild exophthalmos resolved. CONCLUSION: The slipped muscle may have been caused by insufficient suture and/or excessive rubbing of the eye by the patient. When divergent strabismus is observed after recession of the medial rectus muscle, a slipped muscle should be considered as a differential diagnosis.

Treatment for A and V strabismus by slanting muscle insertions.

PURPOSE: To evaluate the therapeutic effects of surgically slanting extraocular muscle insertions. RESEARCH DESIGN: Observational case series. METHODS: We performed slanting recession and resection on medial or lateral rectus muscles. We created a slanting surgical reinsertion line with a 3-4 mm difference between upper and lower corners of the muscles, in 31 patients with A or V strabismus (V exotropia in 16 patients; A exotropia in 12; A esotropia in 3). Cases with V exotropia with moderate or marked overaction of inferior oblique muscle were excluded. RESULTS: V exotropia: The average amount of V pattern was 17.9 PD before and 7.6 PD after surgery. Slanting surgery reduced the V pattern in 15 of 16 patients. The mean amount of reduction was 10.3 PD in the V pattern and 29.8 PD in upgaze. A exotropia: The average amount of the A pattern was 26.6 PD before and 6.3 PD after surgery. Slanting surgery reduced the A pattern in 8 of 12 patients. The mean reduction was 20.3 PD in the A pattern and 36.4 PD in downgaze. A esotropia: The average amount of the A pattern was 23 PD before and 8 PD after surgery, reducing the A pattern in 1 of 3 patients. CONCLUSION: The surgical technique of slanting muscle insertions for correction of A and V strabismus is a suitable procedure for reducing or eliminating A and V patterns.