Normal Anatomy and Anomalies of the Rectus Extraocular Muscles in Human: A Review of the Recent Data and Findings.

Development of modern surgical techniques is associated with the need for a thorough knowledge of surgical anatomy and, in the case of ophthalmologic surgery, also functional aspects of extraocular muscles. Thus, the leading idea of this review was to summarize the most recent findings regarding the normal anatomy and anomalies of the extraocular rectus muscles (ERMs). Particular attention was paid to the presentation of detailed and structured data on the gross anatomy of the ERMs, including their attachments, anatomical relationships, vascularization, and innervation. This issue of ERMs innervation was presented in detail, considering the research that has recently been carried out on human material using advanced anatomical techniques such as Sihler's technique of the nerves staining. The text was supplemented with a carefully selected graphic material (including anatomical specimens prepared specially for the purpose of this review) and discussion of the clinical cases and practical significance of the presented issues.

Does the disruption of horizontal anterior ciliary vessels affect the blood-aqueous barrier function?

PURPOSE: To investigate the significance of the anterior ciliary vessels (ACVs) preservation during the conventional horizontal strabismus surgery. METHODS: Patients (≥ 8 years) with horizontal strabismus were randomly allocated into group 1 (with ACV preservation) and group 2 (without ACV preservation). The surgical eyes in group 1 were further divided into group A (one rectus muscle operated) and group B (two rectus muscles operated). Similarly, eyes in group 2 were divided into group C (one rectus muscle operated) and group D (two rectus muscles operated). The success rate of ACV preservation was calculated. The anterior chamber flare measurements of each eye by laser flare photometry were recorded on the day prior to and after operation. The flare values between groups and between pre- and post-operation in each group were compared by one-way analysis of variance and a paired t-test respectively. RESULTS: In groups A and B, the success rate of ACV preservation was 82% (27/33) and 70% (28/40)respectively, and the flare values between pre- and post-operation showed no significant differences(4.378 ± 1.527, 4.544 ± 1.452, P = 0.526; 4.625 ± 1.090, 4.989 ± 1.468, P = 0.101 respectively). However, the postoperative values were significantly increased in group C and group D(4.661 ± 1.031, 5.039 ± 1.310, P = 0.025; 4.933 ± 1.691, 5.502 ± 1.430, P = 0.000 respectively). The postoperative flare readings of group D were significantly higher than group B, while group A and group C had no significant variation. CONCLUSION: ACV preservation probably has clinical significance in reducing the undesirable influence on the blood-aqueous barrier.

The Gracillimus Orbitis Muscle.

The gracillimus orbitis muscle is an anomalous, accessory, or supernumerary extraocular muscle that, although is rarely seen clinically in the human orbit, has been identified in 5% to 14% of dissected cadaver orbits. It arises from the medial surface of the levator near its origin and runs forward between the levator and superior oblique muscles resembling one of the other extraocular muscles. More anteriorly, it becomes thinner, less well defined, and mostly fibrous. Its major insertion is into the fascia surrounding the trochlea, while other fibers may travel to the supratrochlear artery, intermuscular septum, the levator or medial rectus muscle, and the fascia surrounding the superior ophthalmic vein. The function of this anomalous muscle remains unknown in most cases. Knowledge of its presence is important as the oculoplastic/orbital surgeon may encounter it during an eyelid or orbital procedure.

Ocular dysmotility after intra-arterial chemotherapy for retinoblastoma.

We report the case of a 15-month-old boy with retinoblastoma who developed exotropia secondary to a right medial rectus infarct after intra-arterial chemotherapy. He had unilateral sporadic group C tumor (International Classification of Retinoblastoma) and was treated with intra-arterial melphalan. One week after the first session of intra-ophthalmic arterial melphalan chemotherapy, he was noted to have orbital congestion, exotropia, and right adduction limitation. Magnetic resonance imaging was suggestive of a right medial rectus infarct. The tumor showed a good response to intra-arterial chemotherapy but the exotropia persisted.

Location of the vascular arcade superficial and deep to the Muller muscle related to blepharoptosis surgery.

The aim of this study is to elucidate the location of the vascular arcades of the Muller muscle as it is related to blepharoptosis surgery. A total of 28 eyelids of 14 patients were observed. In 4 hemifaces of 2 fresh Korean adult cadavers, injection of red latex and dissection were performed via a cutaneous and conjunctival approach. Measurements were performed for determination of distances from the upper margin of the tarsal plate to the visible vascular arcades. Two parallel vascular arcades were observed through the conjunctiva. The distance from the upper margin of the tarsal plate to the visible vascular arcade was 6.86 ± 0.53 mm (lower arcade) and 11.71 ± 0.73 mm (upper arcade), respectively. Using the skin approach, an upper vascular arcade was observed between the levator aponeurosis and the Muller muscle. Using the conjunctival approach, a lower vascular arcade was observed between the conjunctival epithelium and the Muller muscle. We hope that these two vascular arcades can be regarded as landmarks for placating the Muller muscle in blepharoptosis surgery.

Arterial vascularization of the extraocular muscles on its importance for orbital approaches.

The anatomic description of the arterial supply of the muscles of the eyeball was studied because medial and lateral approaches to the orbit to treat various disorders might severely damage the main trunk of the ophthalmic artery. The different arterial pedicles for each muscle, as well as their origins and points of penetration into the muscle, were studied in 19 male human orbits. In all cases, the muscular branches originated from the ophthalmic artery, and generally from the inferior face of this artery, just after crossing the optic nerve. The inferomedial muscular trunk arose from the distal of the ophthalmic artery (63.16%). The inferolateral muscular trunk, the superior oblique, levator palpebrae superioris, superior rectus, lateral rectus, and medial rectus arose from the lacrimal artery (43.36%), the bend of the ophthalmic artery (36.84%), the supraorbital artery (36.84%), the distal end of the ophthalmic artery (52.6%), the lacrimal artery (89.47%), and the inferomedial muscular trunk (84.51%), respectively. Complications resulting from damaging the artery can cause inadequacy in eye position, mobility, superior oblique function, or binocular vision, which are expected to be corrected postoperatively.

Accurate course and relationships of the intraorbital part of the ophthalmic artery in the sagittal plane.

INTRODUCTION: Knowledge of variations in the course and distribution of the intraorbital part of ophthalmic artery (OA) is necessary for the diagnosis and treatment of anterior cranial and orbital disorders. MATERIAL: 38 human cadaver dissections to demonstrate the microsurgical anatomy of the intraorbital part of the OA were studied in three stages, considering its neighbourhood with the optic nerve in the sagittal plane. RESULTS: The first part of the OA was located on the inferolateral aspect of the optic nerve in 89.47%. The diameter and the length of the first part of the OA were 1.69+/-0.34 mm and 7.58+/-0.89 mm. 73.68% of the cases crossed the optic nerve superiorly, and 26.31% inferiorly. The diameter and length of the second part of the OA were as 1.52+/-0.29 mm and 4.12+/-0.85 mm. The diameter and length of the third part of the OA were 1.07+/-0.18 mm and 4.12+/-0.85 mm. The first branch of the intraorbital part of the OA was the central retinal artery in 26.31% of the specimens. CONCLUSION: A better understanding of the vascular anatomy of the orbit should allow for the modification of surgical techniques to reduce bleeding during biopsy or excision of orbital structures.

[The effect of preventing anterior segment ischemia by preservation of anterior ciliary vessels in rabbit].

OBJECTIVE: To investigate the effect of preserving anterior ciliary vessels (ACVs) on the prevention of anterior segment ischemia syndrome (ASI) during the surgery of extraocular muscles. METHODS: Thirty-two adult New Zealand white rabbits were randomly divided into four groups. ACVs of the right eyes were preserved among all of the rabbits, and were cut off in all of the left eyes. Group A: internal and external recti were cut off in two eyes; Group B: superior and inferior recti were cut off in two eyes; Group C: internal, external and superior or inferior recti were cut off in two eyes; Group D: all of the recti were cut off in two eyes. All rabbits were observed under slit microscope. The intraocular pressure (IOP), the total protein and lactic acid in the aqueous humor were recorded preoperatively and postoperatively. Eyes were enucleated at the forth week postoperatively to obtain the iris and the ciliary body for histopathologic study and electron microscopy. RESULTS: No signs of ASI were observed in the right eyes of all four groups under the slit lamp and under the light and election microscopes. The IOP and levels of ingredients of aqueous humor (total protein and lactic acid) showed no difference between preoperative and postoperative interval. No obvious ASI was observed in the left eyes of group A. Mild reactions of ASI were observed in the left eyes of group B. Moderate to severe reactions of ASI were observed in the left eyes in group C and group D. The IOP reduced from (17.21 +/- 3.76) mm Hg (1 mm Hg = 0.133 kPa) preoperatively to (14.48 +/- 3.36) mm Hg postoperatively in group C (P < 0.05); and from (16.68 +/- 2.33) mm Hg reduced to(3.17 +/- 0.92) mm Hg in group D. (P < 0.05). The level of total protein and lactic acid in the aqueous humor increased from (505.3 +/- 5.0) mg/L and (7.54 +/- 0.47) g/L preoperatively to (811.9 +/- 44.4) mg/L and (11.00 +/- 3.59) g/L postoperatively in group C, respectively (P < 0.05). In group D, the level of total protein and lactic acid in the aqueous humor increased from (504.6 +/- 4.1) mg/L and (7.17 +/- 1.44) g/L preoperatively to (1025. 8 +/- 78.3) mg/L, (8.23 +/- 1.68) g/L postoperatively, respectively (P < 0.05). There were various histopathological changes under the light and electron microscope in groups C and D. While no obvious ischemic changes were observed in group A. CONCLUSION: Two vertical muscles cut off at one eye simultaneously would produce mild reactions of ischemia, while three or more muscles cut off simultaneously could obstruct blood flow in eyes and induce ASI. Preservation of the ACVs could avoid the occurrence of ASI.

Investigation of hemodynamic changes after strabismus surgery using color Doppler imaging.

PURPOSE: To investigate hemodynamic changes after strabismus surgery using color Doppler imaging (CDI). METHOD: Group 1 patients (n = 13) underwent surgery on a single horizontal rectus muscle, and group 2 (n = 13) underwent surgery on both horizontal rectus muscles. Subjects with no systemic or ophthalmologic disorders were selected as controls (n = 16). In group 1 and group 2, CDI of the ophthalmic artery (OA), the central retinal artery (CRA), and the nasal and temporal posterior ciliary arteries (PCAs) was performed before surgical correction and on postoperative days 1 and 7. For each vessel, peak systolic (V(max)), end diastolic (V(min)), and mean (V(mean)) blood flow velocities were measured, in addition to the resistivity index (RI) and pulsatility index (PI). RESULTS: V(max) in the OA on postoperative day 1 was higher in group 2 than in group 1 (P =.004). V(min) in the OA on postoperative day 1 was significantly higher in group 2 than in the controls (P =.001) and group 1 (P =.001). For group 2, comparison of the OA preoperative findings to the findings on postoperative day 1 showed that V(min) (P =.003) and V(mean) (P =.02) increased significantly, and the RI (P =.01) and PI (P =.006) decreased significantly. These significant differences were not observed on day 7 (P >.05). CONCLUSION: Surgery on both horizontal rectus muscles in an eye causes hemodynamic changes in the OA in the early postoperative period.

Intraorbital anatomy of the koala (Phascolarctos cinereus).

This is the first documented study of the anatomical details of the contents of the normal koala orbit, excluding the bulbus oculi. Baseline data were established which are necessary for understanding and treating ocular disease in the koala (Phascolarctos cinereus). The anatomy of the orbital contents of the koala were examined and described from animals that presented dead or were euthanized for humane reasons. Dissections of the orbital cavity were performed under magnification. Polymethyl methacrylate (PMMA) casts of the nasolacrimal system and the vascular supply of the orbit were also made in order to study these systems. The superficial lymphatic drainage of the conjunctival tissues was studied by subcutaneous injection of Evan's Blue into the palpebral conjunctiva of a freshly deceased animal, and by Microfil casts of the efferent lymphatics. In general, the orbital contents of the koala are consistent with those of other carnivorous polyprotodont and herbivorous diprotodont marsupials.

Delayed orbital hemorrhage after routine strabismus surgery.

PURPOSE: To report a case of delayed rectus muscle hemorrhage after strabismus surgery. METHODS: Case report. RESULTS: Rectus muscle hemorrhage occurred 36 hours after strabismus surgery in a 26-year-old man, causing temporary loss of vision and reduced ocular motility. Urgent lateral cantholysis and orbital exploration to restore hemostasis were undertaken. Full recovery of vision occurred and a small residual motility disturbance was present 3 months postoperatively. CONCLUSION: Delayed rectus muscle hemorrhage poststrabismus surgery is rare but can have sight-threatening effects. When vision is threatened because of optic nerve compromise, urgent orbital exploration may allow full recovery of function.

Traumatic intramuscular orbital haemorrhage.

Retrobulbar haemorrhage is an uncommon but well-documented complication of retrobulbar anaesthetic blocks in ocular surgery. Peribulbar anaesthesia has been advocated to be equally effective but safer. The incidence of retrobulbar haemorrhage with peribulbar blocks is very low. We report a case in which a peribulbar anaesthetic for cataract surgery resulted in sight-threatening retrobulbar haemorrhage within the medial rectus muscle and required an anterior orbitotomy and direct decompression of the muscle. The surgery was successful. This case illustrates a potentially serious complication of peribulbar anaesthesia, with the successful outcome achieved by rapid definitive diagnosis and intervention.

Hemodynamic changes after strabismus surgery.

AIM: The aim of this study was to investigate the hemodynamic changes that may occur in the retrobulbar circulation after strabismus surgery, using color Doppler ultrasonography (CDI). METHODS: Fifteen healthy volunteers (control group, n=15) and sixteen patients diagnosed with strabismus were enrolled in the study. Either recession or resection was planned on one horizontal rectus muscle in the eyes of Group 1 (n=11) and on two horizontal rectus muscles in the eyes of Group 2 (n=10). CDI was performed to measure peak systolic velocity (V(max)), end-diastolic velocity (V(min)) and mean blood flow velocity (V(mean)) in the ophthalmic artery (OA), central retinal artery (CRA) and posterior ciliary artery (PCA) in the control group and in Groups 1 and 2, both preoperatively and 2-7 days postoperatively. RESULTS: The postoperative resistivity indexes in Groups 1 and 2 were found to be different from those in the control group. Preoperative V(max) and postoperative V(min) and V(mean) values of the vessels in Group 2 were different from those in both Group 1 and the control group (p<0. 001). In both treatment groups, the differences between postoperative and preoperative measurements of the parameters in the OA, CRA and PCA demonstrated statistical significance (p<0.001). CONCLUSION: After strabismus surgery on the horizontal recti, there are some alterations in the retrobulbar blood flow with a significant difference between pre- and postoperative blood flow velocities after single and double rectus surgery. The clinical significance of these results needs to be determined because CDI may be a useful tool in the investigation of hemodynamic alterations after anterior segment interventions that may cause anterior segment ischemia.

Anterior segment ischemia after strabismus surgery with microvascular dissection.

Anterior segment ischemia is a rare but well-known complication of extraocular muscle surgery.(1) Several surgical techniques have been used to prevent this complication in high-risk patients. A number of studies have suggested that microvascular dissection and preservation of the anterior ciliary vessels during strabismus surgery may reduce the risk of ischemic complications. (2-4) We present a case in which anterior segment ischemia occurred despite the use of this vessel-sparing technique.

The role of Müller's muscle reconsidered.

It is a traditional teaching that the levator aponeurosis is the main transmitter of the levator palpebrae muscle. However, there are several points that raise doubts in this fundamental concept of the levator aponeurosis as being the primary interconnecting mechanism in upper lid elevation. Despite the structural integrity of the levator complex, drooping of the upper eyelids is seen to develop in situations such as Horner's syndrome and in times of excessive fatigue and sleepiness. Amid the controversy in the literature regarding the specific role of the levator aponeurosis in the lid-elevating mechanism, we have observed that the levator aponeurosis fails to make constant attachment to the tarsal plate. This has led us to speculate on the possible role of the posterior lamella - Müller's muscle - as the primary transmitter of the levator muscle action to the tarsal plate.

High resolution magnetic resonance imaging of neurovascular orbital anatomy.

PURPOSE: This study describes the magnetic resonance imaging (MRI) anatomy of the blood vessels and nerves of the orbit to provide a morphological basis for the interpretation of clinical findings. METHODS: Seven volunteers aged 29 to 54 years underwent high-resolution MRI of the orbit on a 1 Tesla unit (Impact, Siemens, Germany). T1-weighted oblique-sagittal, coronal, and axial images were obtained using a surface coil. Anatomic structures on the magnetic resonance images were identified by comparison with corresponding histologic sections of the orbit. RESULTS: The ophthalmic artery and most of its branches (central retinal artery, posterior ciliary arteries, lacrimal artery, anterior and posterior ethmoidal arteries, supratrochlear artery, supraorbital artery, dorsal nasal artery) are visualized. The superior ophthalmic vein, the lacrimal vein, the medial ophthalmic vein, the inferior ophthalmic vein, the medial and lateral collateral veins, and the vorticose veins are also delineated. Furthermore, branches of the oculomotor nerve, the abducens nerve, the frontal nerve, the nasociliary nerve, the lacrimal nerve and the infraorbital nerve are identified in the magnetic resonance images. CONCLUSION: High-resolution MRI is capable of delineating the orbital arteries, veins, and nerves. This is mainly based on two principles. First, blood vessels appear mostly dark on magnetic resonance images because of the signal void of flowing blood. Second, the bright background of the orbital fat on T1-weighted magnetic resonance images accounts for the good soft-tissue contrast in the orbit. With improved MRI technology and reduced imaging time, high-resolution-MRI may be applied routinely for diagnostic purposes.

Preservation and observation of anterior ciliary vessels in rectus muscles during strabismus surgery.

PURPOSE: To observe the form and number of the anterior ciliary vessels (ACV) in rectus muscles. To train technician in preservation and observation of ACV, so preservation can be done in cases with a risk of anterior segment ischemia (ASI). METHODS: Curved foreign knife, iris hook, plastic rubber band and standard operating loupes (3x.) or microscope were used in the surgery on 34 cases of comitant strabismus and 18 cases of paralytic strabismus. RESULTS: The ACVs per muscle in medial, lateral, superior, inferior rectus were 3.08, 3.26, 3.50 and 3.50 respectively in 89 muscles of 52 surgical strabismus cases. All ACVs in 16 rectus muscles and 90 out of 220 ACVs in 73 rectus muscles were too small or too short to be dissected. The success rate of ACV preservation was 91.5% (119/130). 105 out of 130 vessels were saved using loupe magnification and 14 pit pf 130 vessels were saved under operating microscope. CONCLUSIONS: The number of ACV in rectus muscles are more than 2 in our observation cases. The ACV preservation has the clinical value of allowing us to perform muscle surgery on three or more rectus muscles simultaneously and get final surgical results more earlier after ACV in each muscle are dissected and preserved otherwise staged surgery are needed. The each strabismus surgeon must know this technique.

Volkmann's ischemic contractures and blowout fractures.

Volkmann's ischemic contractures have long been recognized by orthopedic surgeons as a sequela of increased pressure within osseofascial muscle compartments. We present evidence that the same mechanism is a cause of fibrosis and contracture of extraocular muscles following orbital blowout fractures. Surgical treatment of a specific, recognizable type of blowout fracture is proposed.