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PubMed1999

From balance regulation to body orientation: two goals for muscle proprioceptive information processing?

This study was based on the assumption that the central processing of proprioceptive inputs that arise from numerous muscles contributes to both awareness and control of body posture. The muscle-spindle inputs form a "proprioceptive chain" which functionally links the eye muscles to the foot muscles. Here, we focused on the specific contribution of two links in the control of human erect posture by investigating how proprioceptive messages arising from ankle and neck muscles may be integrated by the central nervous system. Single or combined mechanical vibrations were applied to different muscle tendons at either one (ankle or neck) or both (ankle plus neck) body levels. The amplitude and the specific direction of the resulting oriented body tilts were analyzed by recording the center of foot pressure (CoP) through a force platform with four strain gauges. The results can be summarized as follows: (1) the vibration-induced whole-body tilts were oriented according to the muscles stimulated; furthermore, the tilts were in opposite directions when neck or ankle muscles on the same side of the body were stimulated; (2) except for the ankle antagonist muscles, co-vibrating adjacent or antagonist muscles at the same body level (ankle or neck) resulted in body sways, whose orientation was a combination of those obtained by stimulating these muscles separately; and (3) likewise, co-vibrating ankle and neck muscles induced whole-body postural responses, whose direction and amplitude were a combination of those obtained by separate vibration. We conclude that the multiple proprioceptive inputs originating from either one or both body levels may be co-processed in terms of vector-addition laws. Moreover, we propose that proprioceptive information from ankle and neck muscles may be used for two tasks: balance control and body orientation, with central integration of both tasks.

Adult↗

PubMed2006

Persistent diplopia and strabismus after cataract surgery under local anesthesia.

BACKGROUND AND PURPOSE: Diplopia is an infrequent complication described for retrobulbar local anesthesia. The objective of this study is to report the clinical characteristics and treatments for this surgical complication. METHODS: Retrospective study of medical records. PERIOD: 5.3 years ending February 2005. During this period, 20453 cataract surgeries were performed. The anesthesia used was retrobulbar block with ropivacaine diluted with hyaluronidase. Nineteen patients reported diplopia due to strabismus after the cataract surgical procedure and were referred for evaluation at the Extrinsic Ocular Motility Department. RESULTS: Persistent diplopia after cataract surgery occurred in 19 (0.093%) of the 20453 cases. The types of deviations found were: exotropia (n=3), esotropia (n=5), hypertropia (n=1), exotropia + hypertropia (n=5) and esotropia + hypertropia (n=5). Small deviations and dysfunction of the lateral rectus muscles were most commonly seen. Prism was applied to 4 patients, eye muscle surgery was the option in 8 patients, orthoptic treatment was performed in 3 patients and for 2 patients the decision was to only observe progress. Overall, binocular vision was restored in eleven of the nineteen patients. CONCLUSIONS: Persistent diplopia due to strabismus is an infrequent complication after cataract surgery with retrobulbar block. Etiology of this disorder of extrinsic ocular motility is variable, including mixed components. We stress the importance of adequate preoperative history of strabismus and evaluation of extrinsic ocular motility. Considering the reported incidence of this problem is as high as one in 25 cataract surgeries, one should advise the patient of the possibility of persistent postoperative diplopia and the possible need for surgical intervention and/or prism to treat the symptoms.

Adult↗

PubMed2004

Exogenous orienting of attention depends upon the ability to execute eye movements.

Shifts of attention can be made overtly by moving the eyes or covertly with attention being allocated to a region of space that does not correspond to the current direction of gaze. However, the precise relationship between eye movements and the covert orienting of attention remains controversial. The influential premotor theory proposes that the covert orienting of attention is produced by the programming of (unexecuted) eye movements and thus predicts a strong relationship between the ability to execute eye movements and the operation of spatial attention. Here, we demonstrate for the first time that impaired spatial attention is observed in an individual (AI) who is neurologically healthy but who cannot execute eye movements as a result of a congenital impairment in the elasticity of her eye muscles. This finding provides direct support for the role of the eye-movement system in the covert orienting of attention and suggests that whereas intact cortical structures may be necessary for normal attentional reflexes, they are not sufficient. The ability to move our eyes is essential for the development of normal patterns of spatial attention.

Adult↗

PubMed1989

Prednisone and cyclosporine in the treatment of severe Graves' ophthalmopathy.

It is uncertain what is the most appropriate medical therapy for patients with severe Graves' ophthalmopathy. Therefore, we carried out a single-blind, randomized clinical trial to compare the efficacy of prednisone with that of cyclosporine in 36 patients who had been euthyroid for at least two months. The two groups, each consisting of 18 patients, were similar in age, sex, and the duration and severity of ophthalmopathy. The initial dose of cyclosporine was 7.5 mg per kilogram of body weight per day, and that of prednisone was 60 mg per day, which was subsequently tapered to 20 mg per day. During the 12-week treatment period, 11 prednisone-treated and 4 cyclosporine-treated patients responded to therapy (61 percent vs. 22 percent; P = 0.018); response was manifested by decreases in eye-muscle enlargement and proptosis and improved visual acuity and total and subjective eye scores. There were no differences at base line between the patients who later responded and those who did not. Prednisone was tolerated less well than cyclosporine. After 12 weeks, patients who did not respond were treated for another 12 weeks with a combination of cyclosporine and a low dose of prednisone. Among the 9 patients who initially received prednisone, the addition of cyclosporine resulted in improvement in 5 (56 percent); among the 13 patients who received cyclosporine initially, 8 (62 percent) improved after the addition of prednisone. Combination therapy was better tolerated than prednisone treatment alone. We conclude that single-drug therapy with prednisone is more effective than cyclosporine in patients with severe Graves' ophthalmopathy. The combination can be effective in patients who do not respond to either drug alone.

Adult↗

PubMed1992

Stimulation of glycosaminoglycan production in cultured human retroocular fibroblasts.

Histologic examination of the retroocular connective tissues in Graves' ophthalmopathy (GO) reveals lymphocytic infiltration and an accumulation of glycosaminoglycans (GAG), hydrophilic macromolecules produced locally by fibroblasts. We studied the in vitro effect on fibroblast GAG production of several cytokines and growth factors likely to be secreted by these activated lymphocytes or macrophages. Cultures were established from retroocular connective tissue, extraocular muscle perimysium, and pretibial skin obtained from patients undergoing orbital decompression or eye muscle surgery for severe GO and from normal individuals. Confluent cultures were treated with one of the compounds and labeled with [3H]glucosamine or [35S]sulfuric acid for quantitation of [3H]GAG or [35S]GAG accumulation. Of the various compounds examined, only interleukin-1 (IL-1) and transforming growth factor (TGF)-beta significantly stimulated [3H]GAG accumulation in a dose- and time-dependent fashion. There was no difference in sensitivity to the GAG-stimulating effect of IL-1 or TGF-beta between fibroblasts from the four anatomical sites studied or between normal and GO patient fibroblasts. In conclusion, both IL-1 and TGF-beta are potent stimulators of [3H]GAG accumulation by retroocular connective tissue and perimysial fibroblasts, as well as by fibroblasts from the dermal sites studied. Stimulation of GAG production by these cytokines, released from lymphocytes or macrophages infiltrating the retroocular space, may play a role in the accumulation of GAG in the retroocular and perimysial connective tissues in GO.

Cells, Cultured↗

PubMed1982

Diplopia in autoimmune thyroid disease.

Diplopia without obvious exophthalmos, caused by infiltrative endocrine ophthalmopathy, developed in 12 patients with clinical and laboratory confirmation of autoimmune thyroid disease. In eight patients, the diplopia alone prompted medical attention, which led to the diagnosis of autoimmune thyroid disease. A hypotropia secondary to restrictive tightening of the inferior rectus muscle, producing vertical diplopia, was the most common manifestation of the disorder. The ocular muscle imbalance in autoimmune thyroid disease is caused by mechanical orbital restriction of the extraocular muscle, not by an innervational defect. Evidence of orbital restriction of the eye muscles can establish the diagnosis, regardless of the patient's thyroid function.

Adult↗

PubMed2001

Congenital fibrosis of the extraocular muscles associated with cortical dysplasia and maldevelopment of the basal ganglia.

BACKGROUND: Congenital fibrosis of the extraocular muscles (CFEOM) is a rare condition that has been traditionally regarded as a primary eye muscle disease. Recent studies, however, suggest that CFEOM may be the result of a primary neuropathy with secondary myopathic changes. PURPOSE: To describe a previously unrecognized association between congenital fibrosis of the extraocular muscles and structural abnormalities of the brain. DESIGN: Small case series. METHODS: Detailed clinical examinations and neuroradiologic studies were performed on the three affected family members. In addition, genetic analysis of the family was performed. RESULTS: The three affected family members, mother and two children, have the ocular features of 'classic' congenital fibrosis of the extraocular muscles. All showed dilation of the left lateral ventricle secondary to hypoplasia of the body and tail of the ipsilateral caudate nucleus. There was fusion of an enlarged caudate nucleus head with the underlying putamen. Both children showed widespread bilateral cortical dysplasia. Genetic analysis of the family was inconclusive but consistent with linkage to the CFEOM1 locus on chromosome 12. Chromosomal analysis of the affected individuals did not show evidence of a deletion of chromosome 12 and haplotype analysis was not suggestive of a microdeletion. CONCLUSIONS: Cerebral cortical and basal ganglia maldevelopment can be found in individuals with CFEOM. This suggests that neuroimaging should be considered in the initial diagnostic evaluation of these patients, particularly if there is developmental delay.

Abnormalities, Multiple↗

PubMed2004

Classification and surgical management of patients with familial and sporadic forms of congenital fibrosis of the extraocular muscles.

PURPOSE: To outline the clinical features and surgical treatment of patients with familial and sporadic (simplex) forms of congenital fibrosis of extraocular muscles (CFEOM) from 2 countries, and to classify them according to phenotype and mode of inheritance. DESIGN: Observational and experimental study. METHODS: Twenty-eight affected individuals from 20 families with familial or sporadic CFEOM underwent assessment of ocular motility, visual acuity, slit-lamp biomicroscopy, tonometry, and ophthalmoscopy. Seventeen patients had a variety of eye muscle procedures and ptosis repair. RESULTS: There were 1 Iranian family with autosomal dominant CFEOM, 4 Iranian families with autosomal recessive disease, and 15 simplex cases with various CFEOM phenotypes. Two simplex patients had unilateral disease. All other cases were bilateral. Inferior rectus recession improved hypotropia and Bell's phenomenon in the patients with infraducted eyes and chin elevation. Horizontal muscle recession, sometimes combined with opposite muscle resection, corrected horizontal strabismus satisfactorily in most cases. Ptosis was repaired by frontalis sling and/or levator resection. CONCLUSION: Definite recessive CFEOM was present only in Iranian patients. American patients had the classic phenotype of dominant CFEOM, which was also observed in some of the Iranian patients. The surgical management of patients with CFEOM is challenging. Correction of vertical and horizontal strabismus was addressed using large muscle recessions. Ptosis repair should aim at placing the lid level 1 to 2 mm above the pupil in the primary position to avoid exposure keratopathy.

Adolescent↗

PubMed1994

The possible role of nystagmus in motion sickness: a hypothesis.

An alternative hypothesis to that provided by conflict theory is formulated to account for motion sickness. The new approach is predicted on the oculocardiac reflex (i.e., bradycardia produced by extra-ocular muscle traction) (18) and empirical evidence that retrobulbar anesthesia significantly lowers the incidence of emesis after strabismus surgery (14). Eye muscle traction is presumed to elicit afferent signals that ultimately stimulate the vagus nerve (15). The same neuromotor sequence is presumed to occur during reflexive eye movements under vestibular control and during more complicated combinations of reflexive and voluntary eye movements. It is proposed that the blocking of afferent signals from extra-ocular muscle in an otherwise intact vestibulo-ocular system will eliminate the signs and symptoms of motion sickness normally produced in a provocative environment.

Eye Movements↗

PubMed2004

The application of statistical process control to horizontal strabismus surgery.

PURPOSE: Although originally developed to evaluate quality in manufacturing, statistical process control (SPC) techniques may be applicable to other frequently performed standardized processes. SPC analysis has rarely been used in medicine. We employed SPC charts to analyze the outcomes of one- and two-muscle horizontal strabismus surgery for esotropia and exotropia. METHODS: During a 33-month period between October 1, 1998 and July 1, 2001, we evaluated 95 patients undergoing strabismus surgery on either one or two previously unoperated eye muscles in one or both eyes. SPC charts were used to evaluate the success and validity of our surgical guidelines for horizontal recession and resection procedures. Data were divided into 2 groups, patients with esotropia and patients with exotropia, for computerized statistical analysis using QI Analyst (SPSS, Chicago, IL). RESULTS: Our results after horizontal strabismus surgery, both esotropia and exotropia repair, appear to follow the laws of statistical fluctuation or normal random variation. Our dose-response schedule produced a resultant ocular alignment or exit angle that appeared to be in statistical control, ie, variation from orthotropia that can be expected simply from normal random chance error with only a limited number of outliers. CONCLUSION: The resultant ocular alignment or exit angle after one- or two-muscle strabismus surgery may be described by standard models of statistical fluctuation. SPC may be a valuable method to analyze the variability of the results of many ophthalmologic procedures or treatments over time with the ultimate goal of producing better patient outcomes by decreasing variability.

Esotropia↗

PubMedDate not supplied

[Change in the alpha-glucosidase activity of cattle muscle tissue during slow autolysis].

Changes in the alpha-glucosidase activity of the cattle muscular tissue (oxen eye muscle of loin) were evaluated during storage at 2 degrees. Under these conditions both lysosomal and extralysosomal alpha-glucosidase activities underwent no significant changes during a long period of time (12 days). Activity of lysosome-bound alpha-glucosidase was about 10% of total enzyme activity in the homogenate; the remaining part of alpha-glucosidase was contained outside lysosomes.

Animals↗

PubMed2003

[Muscle pedunculated scleral flaps. A microsurgical modification to improve prosthesis motility].

Orbital implants following enucleation are able beyond all doubt to compensate volume adequately and improve artificial eye motility. In recent decades progress has been made concerning implant material. Nevertheless, in most designs wrapping with homoplastic or alloplastic materials is advocated. In this report a microsurgical concept is presented to avoid wrapping material and at the same time to improve prosthesis motility in a hydroxyapatite-silicon implant. In a retrospective study two groups of patients (15 individuals each) were compared concerning prosthesis motility 6 months after surgery. In group 1 the horizontal and vertical eye muscles were sutured cross-wise in front of the implant (as done since the introduction of this type in 1989). In group 2 autologous muscle pedunculated scleral flaps were dissected microsurgically and used to cover the anterior part of the porous hydroxyapatite component of the implant. There was a highly significant better prosthesis motility and so far no complications concerning implant coverage in this second group. The authors consider the use of muscle pedunculated sclera to be a modification to improve the cosmetic outcome which may also reduce the postoperative complication rate in enucleation surgery.

Equipment Failure Analysis↗

PubMed1987

Recession vs marginal myotomy surgery for strabismus: effects on spatial localization.

Palisade endings (PEs) are found at the musculotendinous junction in eye muscles and this is the site of much strabismus surgery. To assess the role of PEs in supplying proprioceptive information about eye position, we compared the effects of marginal myotomy and recession surgeries on tests of eye-hand coordination (open-loop pointing responses) taken before and after surgery in two groups of children having medial rectus weakening procedures for the first time. The results indicate that the myotomy is more proprioceptively "de-afferenting" than the recession, and we assume this is due to the greater disruption of PEs in this procedure.

Child↗

PubMed1969

Extraocular muscle afferents to the cerebellum of the cat.

1. Afferents from the extraocular muscles to the cerebellum of the cat were investigated by evoked potential techniques using muscle stretch as a stimulus.2. Short (about 4 msec) latency responses occurred in the vermian folia anterior (Larsell's lobule V b, c) and posterior (lobules VI and VII) to the primary fissure under light Nembutal anaesthesia.3. The location of the cerebellar eye muscle responses coincides with the visual and auditory projections as well as homologous projections from cortical Areas 8 (the frontal eye fields) and 17 in the monkey. It also overlaps the oculomotor area of the cerebellum as revealed by electrical stimulation.4. Facts 2 and 3 above, together with the selective disturbance of saccadic eye movements in humans with cerebellar atrophy, suggest a cerebellum mediated proprioceptive feed-back loop for the control of saccadic eye movements.

Animals↗

PubMed1988

Eye-head coupling in humans. I. Simultaneous recording of isolated motor units in dorsal neck muscles and horizontal eye movements.

A tonic coupling between the horizontal component of eye position and dorsal neck muscle activity has been demonstrated in the cat and monkey. In order to demonstrate this synergy in humans and study its characteristics, we have measured the relation between the firing rate of individual motor unit of the splenius muscle and voluntary horizontal shifts of gaze using 5 degrees steps, in head-fixed subjects. Eye movement recording was achieved by conventional binocular electro-oculography and the activity of the right splenius muscle was recorded with Bronks coaxial bipolar electrodes inserted manually at the C4-C5 intervertebral level. The activity of 51 motor units in 10 subjects has been recorded. For all subjects, motor units firing rate increased when the gaze shifted to the ipsilateral side, and both increase in firing rate and recruitment were observed. These results demonstrate that the tonic eye head synergy is also present in man.

Action Potentials↗

PubMed1983

[Postnatal development of static vestibulo-ocular reactions in the rabbit--electromyographic studies].

The changes in the electric activity of the extraocular muscles as a consequence of static tilt stimulation were investigated in rabbits of different postnatal ages by the registration of the electromyogram. The postnatal development of the tonic vestibulo-ocular reflex in the rabbit runs parallel with the transition from an irregular fluctuating eye muscle activity during the first postnatal days to a constantly tonic muscle activity depending on the tilt position.

Animals↗

PubMed2005

The callipyge mutation and other genes that affect muscle hypertrophy in sheep.

Genetic strategies to improve the profitability of sheep operations have generally focused on traits for reproduction. However, natural mutations exist in sheep that affect muscle growth and development, and the exploitation of these mutations in breeding strategies has the potential to significantly improve lamb-meat quality. The best-documented mutation for muscle development in sheep is callipyge (CLPG), which causes a postnatal muscle hypertrophy that is localized to the pelvic limbs and loin. Enhanced skeletal muscle growth is also observed in animals with the Carwell (or rib-eye muscling) mutation, and a double-muscling phenotype has been documented for animals of the Texel sheep breed. However, the actual mutations responsible for these muscular hypertrophy phenotypes in sheep have yet to be identified, and further characterization of the genetic basis for these phenotypes will provide insight into the biological control of muscle growth and body composition.

Animals↗

PubMed1998

Clinical evidence of extraocular muscle fiber-type specificity of botulinum toxin.

OBJECTIVE: To compare the effects of botulinum toxin on static and dynamic aspects of eye movements, and thereby elucidate the mechanisms of its action on eye muscles. BACKGROUND: Laboratory evidence indicates that static alignment and saccades are subserved by different extraocular muscle fiber types, and botulinum toxin may cause specific dysfunction of the fibers controlling static alignment. Diplopia is a well-known side effect of periorbital botulinum toxin injections in humans, and may be a clinical correlate of the laboratory findings. METHODS: Search coil recording of eye movements was performed in one patient with systemic botulism, and in three patients with diplopia following periorbital injection of botulinum toxin A. RESULTS: In the patient with acute botulism, eye movement alignment, range, and saccadic velocity profiles were abnormal. In three patients with iatrogenic diplopia, static alignment was abnormal but movement range and saccadic velocities were within normal limits. Edrophonium improved the range of movements and saccadic velocities in the patient with systemic botulism but was ineffective in reversing ocular misalignment in the one iatrogenic patient to whom it was administered. CONCLUSIONS: Precise alignment is subserved by orbital singly innervated muscle fibers, and the effects of botulinum toxin are greatest on these fibers. This predilection is apparent when the toxin dose is very small, as must have been the case in our patients with iatrogenic diplopia. The lack of a response to edrophonium probably reflects structural damage to muscle fibers. In contrast, larger doses of toxin produce an acute dysfunction of all extraocular muscle fiber types, which is responsive to edrophonium and consequently reflects partial blockade at the neuromuscular junction.

Adult↗