[Morphological observation on the anterior ciliary vessels in the horizontal rectus muscles of patients with concomitant horizontal strabismus].

Objective: To observe the number of blood vessels and the anatomical characteristics of the anterior ciliary vessels (ACVs) in the horizontal rectus muscles of patients with concomitant horizontal strabismus. Methods: Cross-sectional study. From July 2016 to September 2019 patients with concomitant horizontal strabismus treated by realignment surgeries in Xiamen Eye Center of Xiamen University were included. Patients who had previous operations on eyes were excluded. The high resolution surgical imaging of ACVs in the horizontal rectus muscles was performed during operation. The photos of ACVs in muscles were tagged and observed to compare the distribution of the various numbers of blood vessels and morphological characteristics of the ACVs in the medial and lateral rectus muscles. In addition, muscle tissues about 4 mm with an intact sheath were gained from patients undergoing the muscle resection. The muscle sections were stained with hematoxylin-eosin staining, and the arteriovenous properties and their distribution in muscles and fascia tissues were observed. The chi-square test was used for statistical analysis. Results: A total of 387 patients with concomitant horizontal strabismus (176 with esotropia, 211 with exotropia) were enrolled in this study, among whom 198 were male and 189 were female. The age ranged from 1 to 68 years (median, 13 years). Photos of ACVs in 742 horizontal rectus muscles from 383 patients were observed. Of the 351 medial rectus muscles, 24 (6.8%) contained 1 major (or bundle of) ACV, 163 (46.4%) contained 2 major (or bundles of) ACVs, and 164 (46.7%) contained 3 or more major (or bundles of) ACVs. Of the 391 lateral rectus muscles, 161 (41.2%) contained 1 major (or bundle of) ACV, 156 (39.9%) contained 2 major (or bundles of) ACVs, and 74 (18.9%) contained 3 or more major (or bundles of) ACVs. The distribution of ACVs in the medial and lateral rectus muscles was statistically different (χ(2)=133.87, P<0.01). According to the number and morphological characteristics of vessels, the ACVs in the medial and lateral rectus muscles were divided into 4 and 3 categories, respectively, as well as various types and subtypes. The rate of patients whose both eyes had the same type of ACVs in the medial or lateral rectus muscles was 31.6% (25/79) and 26.1% (29/111), respectively, and there was no significant difference (χ(2)=0.69, P=0.41). However, the ACVs of the same type from both eyes of the same patient were not identical in morphology. The ACVs in the medial and lateral rectus muscles with collateral circulation accounted for 3.7% (13/351) and 24.3% (95/391), respectively, and the difference was statistically significant (χ(2)=63.07, P<0.01). The hematoxylin-eosin staining of the medial lateral rectus tissues from 4 patients showed that the ACVs contained arteries and veins. The vessels in the medial rectus muscles were distributed in muscle tissue and fascia tissue, while the vessels in the lateral rectus muscles were only distributed in fascia tissue. Conclusions: Compared with the lateral rectus muscles, there are about 50% medial rectus muscles contain more than 3 major (or bundles of) vessels in patients with concomitant horizontal strabismus. The accompanying patterns of arteries and veins of ACVs are varied. ACVs are distributed in muscle tissue of the medial rectus muscles and in fascia tissue of the medial and lateral rectus muscles. (Chin J Ophthalmol, 2020, 56: 197-204).

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.

Distance between intramuscular nerve and artery in the extraocular muscles: a preliminary immunohistochemical study using elderly human cadavers.

PURPOSE: Extraocular muscles are quite different from skeletal muscles in muscle fiber type and nerve supply; the small motor unit may be the most well known. As the first step to understanding the nerve-artery relationship, in this study we measured the distance from the arteriole (25-50 µm in thickness) to the nerve terminal twigs in extraocular muscles. MATERIALS AND METHODS: With the aid of immunohistochemistry for nerves and arteries, we examined the arteriole-nerve distance at 10-15 sites in each of 68 extraocular muscles obtained from ten elderly cadavers. The oblique sections were nearly tangential to the muscle plate and included both global and orbital aspects of the muscle. RESULTS: In all muscles, the nerve twigs usually took a course parallel to muscle fibers, in contrast to most arterioles that crossed muscles. Possibly due to polyinnervation, an intramuscular nerve plexus was evident in four rectus and two oblique muscles. The arteriole-nerve distance usually ranged from 300 to 400 µm. However, individual differences were more than two times greater in each of seven muscles. Moreover, in each muscle the difference between sites sometimes reached 1 mm or more. The distance was generally shorter in the rectus and oblique muscles than in the levator palpebrae muscle, which reached statistical significance (p < 0.05). CONCLUSIONS: The differences in arteriole-nerve distances between sites within each muscle, between muscles, and between individuals might lead to an individual biological rhythm of fatigue in oculomotor performance.

Evaluating the Microcirculation of Normal Extraocular Muscles Using Quantitative Dynamic Contrast-Enhanced Magnetic Resonance Imaging.

PURPOSE: The purpose of this work was to evaluate the microcirculation of normal extraocular muscles using quantitative dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) (DCE-MRI). MATERIALS AND METHODS: The institutional review board approved the study. Forty-eight eyes were examined using quantitative DCE-MRI on a 3-T MRI system. Quantitative parameters, including the volume transfer constant (Ktrans), the fractional volume of extravascular extracellular space (Ve), and the rate constant (Kep) of each extraocular muscles, were analyzed. The type of DEC time-intensity curve (TIC) was evaluated. The parameters of bilateral extraocular muscles were compared using the Wilcoxon test. The difference in quantitative values of different extraocular muscles was compared using independent-samples Kruskal-Wallis test. RESULTS: No statistical differences of parameters were found between the left and right extraocular muscles (P > 0.05). Volume transfer constant values in medial rectus (MR) muscles and inferior rectus (IR) muscles were significantly higher than those in the lateral rectus (LR) muscles and superior rectus (SR) muscles (P < 0.05). The median Ktrans value of the MR (0.170) was higher than that of the IR (0.151); however, the difference was not significant (P > 0.05). In the 4 extraocular muscles, the Ve values of MR are the largest, followed by the IR, LR, and SR values. The DCE time-intensity curves of extraocular muscles are type II or type III. Medial rectus and IR are mainly type III, and LR and SR are mainly type II. CONCLUSION: The quantitative DCE-MRI can be used as an important and noninvasive technique to evaluate the microcirculation of extraocular muscles. Further investigations for other extraocular muscles diseases by using quantitative DCE-MRI are warranted.

Effect of Direct Glare on Orbicularis Oculi and Trapezius During Computer Reading.

PURPOSE: Unfavorable visual conditions during computer work may affect development of both eyestrain and musculoskeletal pain in the neck and shoulder area. The aim of the study was to investigate how direct glare affects symptom development, muscle activity, and muscle blood flow in m. orbicularis oculi and m. trapezius during reading on a computer screen. METHODS: Fifteen healthy young adults with normal binocular vision read text on a computer screen at an optimized computer workplace, 30 minutes with glare exposure and 30 minutes with appropriate lighting. Postural angles were continuously registered. Development of eye symptoms and musculoskeletal pain in the neck and shoulder area were recorded using VAS scales. Muscle activity and muscle blood flow were measured continuously using electromyography and photoplethysmography, respectively. RESULTS: Glare exposure resulted in significantly more pronounced eye pain, increased orbicularis muscle activity, and increased trapezius blood flow compared to reading with appropriate lighting. There were no significant differences in posture between the two light conditions. There were also significant associations between orbicularis oculi activity and both trapezius blood flow and neck pain during both conditions. CONCLUSIONS: Results from the current study show that direct glare conditions cause increased eyestrain and orbicularis oculi contraction during reading on a computer screen. This study also indicates that exposure to direct glare affects the trapezius muscle, possibly by an interaction between the visual system, sympathetic nervous system, and head-stabilizing muscles. In addition, there were associations between the use of orbicularis oculi, trapezius blood flow, and development of neck pain independent of the lighting.

Reliability of muscle blood flow measurements in orbicularis oculi.

PURPOSE: Orbicularis oculi muscle tension and muscle blood flow have been shown to be objective measures of eyestrain during visually demanding activities, such as computer work. In line with this, positive associations between eye-related pain and muscle blood flow in orbicularis oculi have been observed. A hypothesis regarding work situations with cognitive tasks and low-level muscle activity, such as computer work, proposes that muscle pain originates from the blood vessel-nociceptor interactions of the connective tissue of the muscle. Noninvasive muscle blood flow measurements in the orbicularis oculi muscle are preferable to using an invasive technique. The aim of this study was to test reproducibility and stability of muscle blood recordings in orbicularis oculi using photoplethysmography. METHODS: In the reproducibility tests, 12 subjects were tested twice within 1 to 5 weeks. To study the stability of the method, six of the subjects were randomly selected and tested four more times within 2 to 6 weeks. Test subjects were doing identical visually demanding computer work for 10 minutes in each test. RESULTS: The short-term repeatability of muscle blood flow measurements was considered good, but the stability of blood flow recordings over time in orbicularis oculi was low because of a greater within-subject maximum variability compared with between-subject average variability. CONCLUSIONS: Investigators should be aware of the effect of time, possibly attributed to confounding factors such as environmental changes and mental stress, when comparing photoplethysmography muscle blood flow recordings.

Application of retaining the vessels around the orbicularis oculi muscle in blepharoplasty.

OBJECTIVE: To investigate the effect of retaining the vessels around the orbicularis oculi muscle on reducing local swelling after blepharoplasty. METHODS: A total of 309 patients undergoing blepharoplasty (total incision) were observed and randomly assigned to three groups; (A) conventional operation; (B) preservation of deep vessels; (C) preservation of anterior vessels of orbicularis oculi muscle. The groups were compared based on intraoperative blood loss, operation time, swelling, satisfaction, and complications. RESULTS: Among the 309 patients, 39 were lost to follow-up. c Additionally, A had the shortest operation time, followed by C with slightly longer duration. On the 7th day, 15th day, and 1 month after surgery, both B and C demonstrated significantly lower levels of swelling compared to A. Moreover, patient satisfaction was higher in B and C than in A. CONCLUSION: Retaining either superficial or deep veins of the orbicularis oculi muscle can effectively reduce short-term postoperative swelling. However, when retaining the superficial central group of this muscle during surgery, it is crucial to strictly control the amount of surrounding tissue around vessels.

Eye-related pain induced by visually demanding computer work.

PURPOSE: Eye strain during visually demanding computer work may include glare and increased squinting. The latter may be related to elevated tension in the orbicularis oculi muscle and development of muscle pain. The aim of the study was to investigate the development of discomfort symptoms in relation to muscle activity and muscle blood flow in the orbicularis oculi muscle during computer work with visual strain. METHODS: A group of healthy young adults with normal vision was randomly selected. Eye-related symptoms were recorded during a 2-h working session on a laptop. The participants were exposed to visual stressors such as glare and small font. Muscle load and blood flow were measured by electromyography and photoplethysmography, respectively. RESULTS: During 2 h of visually demanding computer work, there was a significant increase in the following symptoms: eye-related pain and tiredness, blurred vision, itchiness, gritty eyes, photophobia, dry eyes, and tearing eyes. Muscle load in orbicularis oculi was significantly increased above baseline and stable at 1 to 1.5% maximal voluntary contraction during the working sessions. Orbicularis oculi muscle blood flow increased significantly during the first part of the working sessions before returning to baseline. There were significant positive correlations between eye-related tiredness and orbicularis oculi muscle load and eye-related pain and muscle blood flow. Subjects who developed eye-related pain showed elevated orbicularis oculi muscle blood flow during computer work, but no differences in muscle load, compared with subjects with minimal pain symptoms. CONCLUSIONS: Eyestrain during visually demanding computer work is related to the orbicularis oculi muscle. Muscle pain development during demanding, low-force exercise is associated with increased muscle blood flow, possible secondary to different muscle activity pattern, and/or increased mental stress level in subjects experiencing pain compared with subjects with minimal pain.

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.

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.

Intraorbital Arteriovenous Fistula Presenting with Impaired Extraocular Movement After a Provocation Test at the Third Segment of the Ophthalmic Artery.

BACKGROUND: Distal catheterization in the ophthalmic artery beyond the origin of the central retinal artery has been attempted to avoid visual complications in cases of transarterial embolization (TAE). Although avoiding visual complications is important, extraocular complications have been rarely reported and discussed. Here, we report a case of an intraorbital arteriovenous fistula (AVF) presenting with impaired extraocular movement after a provocation test and discuss the potential risks associated with TAE at the third segment of the ophthalmic artery. CASE DESCRIPTION: A 53-year-old man was referred to our hospital for a newly diagnosed vascular lesion on the left optic chiasm. A left internal carotid angiogram revealed an intraorbital AVF fed by distal branches of the left ophthalmic artery taking a recurrent course toward the proximal ophthalmic artery, and the anterior branches of the inferior lateral trunk draining into the tortuous basal vein of Rosenthal with a varix. Neither the cavernous sinus nor the superior ophthalmic vein was opacified as draining routes of this lesion. A provocation test was done for diagnostic and therapeutic purposes at the third segment of the ophthalmic artery. During the test, the patient developed a transient impaired adduction of the left eye without any visual field deficit; therefore, TAE was avoided. The patient made an uneventful recovery and was recommended a transcranial transvenous embolization for a radical treatment. CONCLUSIONS: In intraorbital hypervascular lesions, occlusion of the third segment of the ophthalmic artery is associated with a potential risk of extraocular complications.

Measurement of contractile force of skeletal and extraocular muscles: effects of blood supply, muscle size and in situ or in vitro preparation.

Contractile forces can be measured in situ and in vitro. To maintain metabolic viability with sufficient diffusion of oxygen, established guidelines for in vitro skeletal muscle preparations recommend use of relatively thin muscles (< or =1.25 mm thick). Nevertheless, forces of thin extraocular muscles vary substantially between studies. Here, we examined parameters that affect force measurements of in situ and in vitro preparations, including blood supply, nerve stimulation, direct muscle stimulation, muscle size, oxygenated or non-oxygenated buffer solutions and the time after interruption of vascular circulation. We found that the absolute forces of extraocular muscle are substantially lower when examined in vitro. In vitro preparation of 0.58 mm thick extraocular muscle from 3-week-old birds underestimated contractile function, but not of thinner (0.33 mm) muscle from 2-day-old birds. Our study shows that the effective criteria for functional viability, tested in vitro, differ between extraocular and other skeletal muscle. We conclude that contractile force of extraocular muscles will be underestimated by between 10 and 80%, when measurements are made after cessation of blood supply (at 5-40 min). The mechanisms responsible for the declining values for force measurements are discussed, and we make specific recommendations for obtaining valid measurements of contractile force.

The anatomy of the muscle insertion (scleromuscular junction) of the lateral and medial rectus muscle in humans.

PURPOSE: To analyze the histologic features of the insertion of the medial and the lateral rectus muscles in humans. METHODS: Postmortem study performed on 49 extraocular muscles from 21 subjects without known ocular disease. All muscles were obtained no longer than 8 hours after death, after consent for autopsy. Thirty-seven lateral recti muscles and 12 medial recti muscles were studied with light microscopy (hematoxylin-eosin and Goldner stains) as well as with enzyme histochemistry and immunohistochemistry, with monoclonal-human tenascin C antibody. RESULTS: Light microscopic studies of muscle insertions of the lateral and the medial rectus muscle demonstrated muscle tissue connecting directly to the sclera without a tendon. These findings were confirmed immunohistochemically with tenascin C-antibody staining. CONCLUSIONS: Based on the results of this postmortem study in humans the term "muscle tendon" should be used with caution for the insertional area (scleromuscular junction) of the lateral and medial extraocular muscles. Light microscopy, histochemistry, and immunohistochemistry demonstrate that the tissue at the scleromuscular junction contains striated muscle with minimal connective (tendinous) tissue connecting to the sclera. To the best of the authors' knowledge, this is the first study in which enzyme histochemistry and immunohistochemistry have been used to investigate the anatomy of the insertional area (muscle-tendon-sclera junction) of the extraocular muscles in humans.

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.

Capillaries of human overacting extraocular muscles.

The capillaries of overacting inferior oblique muscles from children with strabismus and of dog inferior oblique muscles were ultrastructurally described. Biopsy material was used in all instances. The mean diameter of the capillary lumen was 2.03 microns for the human inferior oblique and 2.76 microns for the dog inferior oblique. Quantitative estimates of capillary basement membrane width were obtained by two different methods of measurement. The capillaries of human and dog inferior oblique muscles were compared with capillaries of human gastrocnemius muscle and of dog quadriceps muscle. The data were statistically evaluated. It was found that the mean basement membrane width of capillaries of overacting inferior oblique muscles is quite similar to that of the dog normal inferior oblique muscles, showing 2,049 A in overacting muscles and 1,976 A in normal muscles. With both methods of measurement, the mean basement membrane width of inferior oblique muscles appeared thicker than the mean basement membrane of capillaries of the leg muscles in man and in dog as well. It is suggested that the thickening of the capillary basement membrane of inferior oblique muscles represents a regional characteristic. Marked variation in the thickness of the basement membrane was encountered in all muscles.

The effect of complete tenotomy on blood flow to the anterior segment of the canine eye.

The relative importance of the anterior ciliary arteries to blood flow to the anterior segment and the quadrant distribution of blood to the iris, ciliary body, and ciliary processes were determined in canines with the use of 15 +/- 3 mum 103Ru microspheres with the reference blood flow method. Recti muscles were isolated in both eyes. Then with one eye serving as a sham-operated control, anterior ciliary artery blood flow was disrupted by recti tenotomy immediately prior to microsphere injection. Tenotomy resulted in a significant decrease in blood flow to the anterior segment (0.14 +/- 0.03 ml/min/gm vs. 0.26 +/- 0.05 in the untenotomized control) and to the unit iris, ciliary body and ciliary processes (I, CB, CP) (0.92 +/- 0.16 ml/min/gm vs. 1.44 +/- 0.22 in the untenotomized control). Blood flow values for the anterior segment and the unit I, CB, CP in the tenotomized eye were 50% to 60% of those of the control eyes, indicating that the majority of blood flow to the canine anterior segment is not disrupted by complete tenotomy. In the control eye, blood flow values for the medial quadrant of the unit I, CB, CP were significantly higher (p < 0.05) than those of the inferior or superior quadrants. Blood flow values for all quadrants in tenotomized eyes were 55% to 70% of those for control eyes. Therefore the anterior ciliary arteries do not contribute the majority of blood flow to the canine anterior segment.