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PubMed1982

Vestibular mechanisms related to vertical and torsional eye movements.

1. A series of experiments concerning the organization of the vertical vestibuloocular reflex (VOR) of the rabbit are reviewed. 2. Unanesthetized, encéphale isolé and intact, alert rabbits have been submitted to natural stimulation of the labyrinth consisting in sinusoidal oscillations and static tilts around the longitudinal axis. The oculomotor responses have been recorded at the level of the III nucleus oculomotor neurons (OMN) and from the four vertical eye muscles. 3. The phase and gain of the OMN response at different frequencies of oscillation indicate a serial involvement of the macular ampullar labyrinthine receptors in the activation of the OMN. In the low frequency range of head movements, macular receptors alone can provide adequate ocular compensation. By raising the frequency of head movements, the threshold value of acceleration for recruiting second order vestibular neurons related to semicircular canals is reached and the vertical VOR is controlled predominantly by the ampullar receptors of the vertical canals. 4. These results have been confirmed and extended in the alert, intact rabbit. By orienting the animal in different positions with respect to the axis of oscillation it has been possible to activate selectively one or the other pair of complementary vertical canals. The EMG responses recorded from the vertical eye muscle exhibited different magnitudes in the different orientations, while the phase curve remained the same. 5. The static otolith-ocular reflex has also been investigated by tilting the alert animals oriented in the same way. The pattern of the EMG responses elicited by the pure macular input coincides with that obtained during dynamic stimulation. The existence of separate functional macular regions specifically connected with the different eye muscles and a close convergent action of the two types of labyrinthine receptors in ocular compensation, are suggested.

Animals↗

PubMed1984

The differential diagnostic problems in unilateral euthyroid Graves' ophthalmopathy.

Nine consecutive patients with unilateral ophthalmopathy with suspected endocrine pathogenesis were investigated with a TRH test, a T3 suppression-test, thyroid autoantibodies and a subsequent computerized tomography (CT)-scan. All patients were clinically and biochemically euthyroid. Seven of 9 patients had a normal TRH test and 6 of 7 had a normal T3 suppression test. Slightly to moderately elevated microsomal and thyroglobulin (determined with radioimmunoassay) autoantibodies were found in 5 of 8 patients and in 1 patient thyroid stimulating immunoglobulins (TSI) were found. Three of the patients had normal thyroid function tests and no detectable thyroid autoantibodies. The subsequent CT-scan revealed that one of these had a maxillary tumour protruding into the orbita. The remaining 8 patients had enlargement of one (3 patients) or more (5 patients) eye muscles. Two of the 8 patients had bilaterally enlarged eye muscles, one of which was the patient with positive TSI. The remaining 6 patients had unilateral extraocular muscle enlargement. Thus, 2 of 9 patients had ophthalmopathy without thyroid dysfunction so-called isolated autoimmune ophthalmopathy or Graves' ophthalmopathy. Thyroid function tests seem to be of limited value in the diagnosis between endocrine and non-endocrine eye disease, and we recommend the use of diagnostic imaging (e.g. CT-scan) in patients with unilateral exophthalmus in order to diagnose malignant processes.

Antibodies↗

PubMed1988

Afferent signals from cat extraocular muscles in the medial vestibular nucleus, the nucleus praepositus hypoglossi and adjacent brainstem structures.

The responses of single units in the vestibular nuclei, nucleus praepositus hypoglossi and in the brainstem, deep and posterior to the abducens nucleus, were studied in anaesthetized, paralysed cats. Natural vestibular stimulation was provided by horizontal, sinusoidal oscillation of the animal and extraocular muscle afferents of the ipsilateral eye were activated either by passive eye-movement or by electrical stimulation of the inferior oblique branch of the oculomotor nerve in the orbit. Unit responses to vestibular and/or orbital stimuli were examined in sets of peristimulus time histograms interleaved in time. Of 127 units exposed to both types of stimulus, 40 (32%) responded only to vestibular input; 46 (32%) were affected only by the orbital afferent signal and 19 (15%) received both signals; the remaining 22 units (17%) were discarded because they had polymodal (usually somaesthetic) input. Of the 93 units whose recording sites were determined histologically, 24 were in the medial vestibular nucleus, 16 in the n. praepositus hypoglossi and 45 in the magnocellular nucleus of the reticular formation posterior and deep to the abducens nucleus. In these three nuclei 19 units in total were found which carried the orbital proprioceptive afferent signal and also responded to horizontal vestibular stimulation. The input from the eye muscles proved able to modify the vestibular response by adding excitation or inhibition or both. Effects of the orbital signal were generally phasic. About half of the units which responded to passive eye-movement showed statistically significant differences between their responses to horizontal and to vertical eye-movement. We have shown previously that signals from extraocular muscle proprioceptors reach the vestibulo-oculomotor system in an amphibian and a bony fish; the present experiments show that this is the case in a mammal also. The fact that the visual and visuomotor behaviour of these three species is very different suggests that the proprioceptive signal may play some rather fundamental role in the vestibulo-ocular system. The principal interest of the present results is that they demonstrate that units in the central vestibular system of the cat, in structures which are known to be concerned in oculomotor control, and particularly in the organization of horizontal eye-movement, receive an afferent signal from the eye muscles during passive eye-movement. These brainstem nuclei are known to receive various combinations of input from the vestibular and visual systems and of signals which represent neck movement and eye position and velocity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2003

Assessment of extraocular muscles position and anatomy by 3-dimensional ultrasonography: a trial in craniosynostosis patients.

PURPOSE: To determine whether 3-dimensional ultrasonography (3D US) provides information about anatomy and position of extraocular muscles to better guide surgeons approaching strabismus in patients with craniosynostosis who often have anomalous or absent eye muscles. METHODS: The 4 rectus eye muscles were imaged using 3D US for 7 children with craniosynostosis before or after strabismus surgery. Reconstructed 3D images were interpreted as having normal or abnormal anatomy and position, based on comparison with images acquired from 6 normal eyes. Interpretation was validated against the intraoperative findings from strabismus surgery. RESULTS: A total of 34 scans from the study group were used for comparison and validation purposes. Accuracy of anatomical assessments was 85% +/- 12% (percentage +/- confidence interval) and of positional assessments was 62% +/- 16%. Sensitivity and specificity of anatomical assessments was 80% +/- 14% and 88% +/- 10%, respectively. Anatomic anomalies detected by 3D US included excessively thick, thin, scarred and fibrotic, and absent muscles. Sensitivity and specificity of positional assessments was 48% +/- 17% and 85% +/- 12%, respectively. Positional anomalies such as muscle displacement off the normal clock hour axis or posteriorly displaced insertion were also detected. CONCLUSIONS: The 3D US may have an adjunctive role in determining anatomy and position of rectus muscles in patients with craniosynostosis, although it was more accurate in assessing anatomic features rather than positional features of rectus muscles.

Adolescent↗

PubMed2001

MRI measurements of orbital tissues in dysthyroid ophthalmopathy.

BACKGROUND: Muscle volume investigation by different imaging techniques has proven useful in the diagnosis and follow up of treatment in dysthyroid ophthalmopathy. However, no study on muscle volume measurement by magnetic resonance imaging (MRI) has been done in this disease. METHODS: Six patients with monocular or asymmetric binocular dysthyroid ophthalmopathy and eight controls were examined with orbital MRI using a surface coil. In the muscle volume study, 2 mm coronal slices were used for measuring the six extraocular muscles (EOM), i.e., medial rectus (MR), lateral rectus (LR) superior rectus (SR), inferior rectus (IR), superior oblique (SO), and inferior oblique (IO) muscles, as well as the orbital fatty tissue (OFT). In the muscle thickness study, 3 mm transverse and sagittal images were used for measuring the four rectus muscles during fixation in different gaze positions in horizontal and vertical planes. RESULTS: In dysthyroid ophthalmopathy, the muscle volume of the six external eye muscles was significantly larger than in controls, except for the IO. The IR and MR showed the largest increase in muscle volume. The correlation between muscle thickness and different degrees of eye deflections was linear for all four rectus muscles both in patients and controls, and no significant differences in the slopes of the regression lines were found. The volume of OFT was significantly larger in patients than in controls, and the change in volume was larger than that of muscle volume. CONCLUSIONS: MRI technique makes it possible to observe and evaluate quantitatively the volume of all six extraocular muscles and the orbital fatty tissue in dysthyroid ophthalmopathy. It also makes it possible to evaluate changes in morphology during eye muscle contraction.

Adipose Tissue↗

PubMed2001

Neural and mechanical factors in eye control.

Soft tissue "pulleys" in the orbit alter the paths of the eye muscles in a way that may simplify the brain's work in implementing Listing's law, i.e., in holding ocular torsion at zero. But Listing's law does not apply to some oculomotor systems, such as the vestibuloocular reflex (VOR), which shows a different kinematic pattern. To explain this different pattern, some authors have assumed that the pulleys must adopt a different configuration, retracting along their muscles when the eye switches from Listing's law to VOR mode. The proposed retraction has not so far been observed, although the pulleys do move in other ways. We show that the hypothetical retraction of the pulleys would not in fact explain the full kinematic pattern seen in the VOR. But this pattern can be explained entirely on the basis of pulley positions and motions that have actually been observed. If one takes into account the neural processing within the VOR, specifically the fact that the reflex is weak in the torsional dimension, then a single mode of pulley action can serve both vestibuloocular kinematics and Listing's law.

Biomechanical Phenomena↗

PubMed2006

Polytetrafluoroethylene (Goretex) for muscle elongation in the surgical treatment of strabismus with restricted motility.

PURPOSE: Repeated strabismus surgery as well as eye muscle fibrosis in various forms of strabismus, can be followed by restriction of the motility of the eye. Tendon elongation may be necessary if further improvement of the deviation and duction of the eye muscle is to be achieved. We used polytetrafluoroethylene (Goretex) and looked at its user comfort, compatibility and dose-rate relationship. METHOD: Three patients with consecutive exotropia after repeated operations for congenital esotropia, two patients with VI nerve palsy and residual head turn after combined convergence operation and one child with congenital fibrosis syndrome underwent muscle tendon elongation with Goretex (7-15 mm) of either the medial or the lateral rectus muscle, which had already been resected and/or recessed in former surgeries. Forced duction under general anaesthesia was restricted in all patients. RESULTS: The correction of the deviation in primary position (deviation at distance + 3 degrees to - 4 degrees and at near - 1 degrees to - 8 degrees ) and in side gaze was satisfactory and motility was clearly improved. There were no postoperative complications (infection, shrinkage, scarring) and the postoperative results in terms of the angle of deviation and the improvement in motility remained stable for 1-6 years. CONCLUSION: Polytetrafluoroethylene (Goretex) is a good material with which to resolve complicated cases of strabismus in which muscle tendon elongation for bulbus restriction is necessary.

Adult↗

PubMed1989

Clinical presentation of Graves' ophthalmopathy.

The eye findings of Graves' ophthalmopathy were prospectively recorded in 90 consecutive untreated patients (66 females, 24 males; mean age 44.5 years) according to the 1977 NOSPECS classification. Soft-tissue involvement was observed in 90%, proptosis greater than or equal to 23 mm in 30%, eye muscle involvement in 60%, corneal involvement in 9% and sight loss in 34%. No differences in the distribution of eye changes between right and left eye were found. Values for proptosis (mean +/- SD, 20.2 +/- 3.6 mm) had a near-normal distribution. Orbital computed tomography (CT) scanning (performed in 80 cases) demonstrated enlargement of inferior rectus in 60%, medial rectus in 50%, superior rectus in 40% and lateral rectus in 22%. Unilateral eye disease was present in 13 patients (14%); in 4 of these patients the CT scan showed eye muscle enlargement also in the fellow eye and in 2 patients bilateral eye disease subsequently developed. The distribution of age, sex and NOSPECS classes in patients with unilateral eye disease was similar to that in patients with bilateral eye disease, but the interval between the onset of thyroid and eye disease was much shorter in cases of unilateral than in cases of bilateral eye disease. Patients without clinically evident thyroid disease (n = 20, 22%) were not different from patients with thyroid disease in age, sex or ophthalmological presentation. The various data suggest: (1) the 1977 NOSPECS classification under-represents significant proptosis in 12% of cases; (2) the age and sex distribution of patients with Graves' ophthalmopathy is similar to that of cases with thyroidal Graves' disease, and (3) unilateral Graves' ophthalmopathy may represent an early stage of the disease, that as a rule already is or develops shortly afterwards into a bilateral disease.

Adult↗

PubMed2006

Biological organization of the extraocular muscles.

Extraocular muscle is fundamentally distinct from other skeletal muscles. Here, we review the biological organization of the extraocular muscles with the intent of understanding this novel muscle group in the context of oculomotor system function. The specific objectives of this review are threefold. The first objective is to understand the anatomic arrangement of the extraocular muscles and their compartmental or layered organization in the context of a new concept of orbital mechanics, the active pulley hypothesis. The second objective is to present an integrated view of the morphologic, cellular, and molecular differences between extraocular and the more traditional skeletal muscles. The third objective is to relate recent data from functional and molecular biology studies to the established extraocular muscle fiber types. Developmental mechanisms that may be responsible for the divergence of the eye muscles from a skeletal muscle prototype also are considered. Taken together, a multidisciplinary understanding of extraocular muscle biology in health and disease provides insights into oculomotor system function and malfunction. Moreover, because the eye muscles are selectively involved or spared in a variety of neuromuscular diseases, knowledge of their biology may improve current pathogenic models of and treatments for devastating systemic diseases.

Animals↗

PubMed2000

Counterrotation of the globe in macular translocation.

BACKGROUND: Macular translocation is a new treatment option in age-related maculopathy. The aim of this study was to report experience with the handling of the sensory problems concerning subjective cyclorotation and binocularity that arise with this technique. METHODS: The data of 33 patients who had undergone macular translocation and counterrotation of the globe by muscle surgery in a first operation, followed by silicone oil removal and sometimes revision of the eye muscles in a second operation, were evaluated. The counterrotation consisted of a partial transposition of the rectus muscles and extensive surgery on the anterior margins of the oblique eye muscles. Subjective monocular cyclorotation, motility and binocularity were tested. RESULTS: In 5 patients after the two operations binocular single vision was proved; in one of these cases there was even stereoscopic function. Seventeen patients excluded one eye: 13 excluded the operated eye, 4 the fellow eye. Eleven patients experienced double vision or tilted images under binocular viewing conditions and thus required further surgery or occlusion of one eye. CONCLUSION: The majority of patients were not hindered by subjective cyclorotation. Nevertheless, in a large proportion of patients binocularity could not be reestablished because of still reduced visual acuity or cyclotropia. The data show that the aim of restoring binocularity can be achieved but in practice is often not attained.

Aged↗

PubMed1997

Treating severe Graves' ophthalmopathy.

Most patients with Graves' disease have some evidence of ocular involvement, but this is commonly mild, requiring only local measures. A minority of patients (3-5%) have severe Graves' ophthalmopathy, for which the three main treatment procedures are represented by high-dose glucocorticoids, orbital radiotherapy and orbital decompression. Favourable results with medical treatment have been reported in approximately 60% of patients, with particular regard to inflammatory changes, newly developed eye muscle dysfunction and optic neuropathy. Orbital decompression is indicated in severe eye disease not responsive to glucocorticoids and/or irradiation, particularly in the presence of marked proptosis and optic neuropathy. Not conclusive or unsatisfactory results have been obtained with other medical treatment procedures, including immunosuppressive drugs, intravenous immunoglobulins and plasmapheresis. Recently favourable responses have been reported with somatostatin analogues. Rehabilitative surgery involving either the eye muscles or the eyelids is not infrequently required after medical treatment or decompression. Permanent control of thyroid hyperfunction by radioiodine or thyroidectomy is advisable when severe ophthalmopathy is present. Exacerbation of ophthalmopathy following radioiodine may occur but can be prevented by concomitant administration of glucocorticoids. Smoking deleteriously influences the course of ophthalmopathy and its response to treatment.

Glucocorticoids↗

PubMed1991

[Conservative therapy frequently indicated in blow-out fractures of the orbit].

The results of the conservative approach in the management of patients with orbital blow-out fractures were studied at the Orbital Centre, Amsterdam. In 54 out of 111 patients with a pure blow-out fracture, high resolution CT was performed. In these 54 patients with diplopia, clinical examination together with the analysis of direct multiplanar high resolution CT revealed four cases of impaired motility. These were oedema, oculomotor nerve palsy, enophthalmos and adhesions around the lower eye muscles and the orbital floor. Patients were immediately instructed to exercise eye movements thoroughly. If diplopia did not resolve, further management was decided on. In all patients with edema or oculomotor nerve palsy, diplopia resolved spontaneously. Surgery was necessary to reduce diplopia in the enophthalmos and adhesion groups. This study shows that eye movement exercises together with a 'wait and see' approach diminish the number of operations by 50% in patients with pure blow-out fractures. It also circumvents the iatrogenic adhesions between eye muscles and orbital floor, which are difficult to treat.

Combined Modality Therapy↗

PubMed2003

Incomitance of ocular rotation axes in trochlear nerve palsy.

Strabismus due to palsy of a single muscle in one eye is always incomitant, which is a consequence of Hering's law of equal innervation. We asked whether this law had similar consequences on the orientation of ocular rotation axes. Patients with unilateral trochlear nerve palsy were oscillated about the nasooccipital (= roll) axis (+/-35 degrees, 0.3 Hz), and monocularly fixed on targets on a head-fixed Hess screen. Both the covered and uncovered eyes were measured with dual search coils. The rotation axis of the covered eye (paretic or healthy) tilted more nasally from the line of sight when gaze was directed toward the side of the healthy eye. The rotation axis of the viewing eye (paretic or healthy), however, remained roughly aligned with the line of sight. We conclude that incomitance due to eye muscle palsy extends to ocular rotation axes during vestibular stimulation.

Adolescent↗

PubMed2001

Split rectus muscle modified Foster procedure for paralytic strabismus: a report of 5 cases.

PURPOSE: To describe a new eye muscle surgical technique and its outcome in a small series of patients. METHODS AND STUDY: The Foster augmented rectus muscle transposition procedure, which utilizes posterior "lateral" fixation sutures [retroequatorial scleral myopexy parallel and adjacent to the lateral rectus muscle] to obtain greater effect from the transpositions, is modified, to preserve ciliary vessels, by doing only a partial 75-80% transposition of the rectus muscles, preserving and leaving behind a small portion of the muscle containing a ciliary vessel. RESULTS: In five patients in whom preserving ciliary vessel supply was particularly important, the procedure produced results in improving binocular alignment and motility equal to that of the unmodified Foster augmented transposition. There were no complications or undesirable results. CONCLUSION: The modified ciliary vessel preserving procedure can be applied in most cases and may be especially useful in those where this is a high likelihood of additional eye muscle surgery being necessary in the future.

Adolescent↗

PubMed1992

Distribution of the nuclear thyroid-hormone receptor in extraocular and skeletal muscles.

The correlation between the occurrence of Graves' ophthalmopathy and Graves' hyperthyroidism may indicate a role for tri-iodothyronine (T3) hormone in the pathogenesis of Graves' ophthalmopathy. In Graves' ophthalmopathy the recti eye muscles are greatly enlarged whereas skeletal muscles seem unaffected. The distribution of the nuclear T3 receptor was studied in normal human and rat eye and skeletal muscles with immunohistochemistry using mouse (monoclonal) antibodies, and by in-situ hybridization for the detection of mRNA encoding the T3-receptor protein. Nuclear staining with T3-receptor antibodies was found in all types of tissues studied. Cytoplasmic staining occurred predominantly in the muscle fibres of the orbital layer of the eye muscles and was generally absent or very low in skeletal muscle fibres and hepatocytes. Immunostaining could be inhibited by preabsorbing the antibodies with bacterially expressed T3-receptor protein, implying specificity. The presence of nuclear and cytoplasmic hormone-free T3 receptor sites was indicated after preincubation of sections with T3 hormone; T3-receptor immunostaining decreased and T3-hormone staining increased. In-situ hybridization clearly revealed the presence of alpha-1 and beta-1 forms of the T3-receptor mRNA in liver, skeletal muscles, and orbital and intermediate layers of the eye muscles. The data demonstrate the presence of T3 hormone-receptor molecules in the extraocular and skeletal muscles. The different susceptibilities of these muscles to Graves' hyperthyroidism may relate to the quantitative differences in T3 hormone-receptor distribution.

Adolescent↗

PubMed1991

Orbital radiotherapy combined with high dose systemic glucocorticoids for Graves' ophthalmopathy is more effective than radiotherapy alone: results of a prospective randomized study.

We have carried out a prospective study to investigate whether orbital radiotherapy combined with high dose systemic glucocorticoids is more effective than orbital radiotherapy alone for Graves' ophthalmopathy. Thirty consecutive patients with relevant and active Graves' ophthalmopathy were randomly assigned to treatment either with orbital radiotherapy combined with systemic glucocorticoids (Group 1, n = 15) or with orbital radiotherapy alone (Group 2, n = 15). The final evaluation was made 6-9 months after beginning treatment. Two patients in each group were lost to follow-up. Ocular involvement and response to treatment were evaluated by the ophthalmopathy index and by clinical assessment. Mean ophthalmopathy index values were 5.85 in Group 1 and 5.46 in Group 2 (p = NS) before treatment, and 2.46 in Group 1 and 3.61 in Group 2 after treatment (p = 0.0001 and p = 0.003 vs initial value, respectively). The mean ophthalmopathy index decrease in Group 1 (-3.39) was significantly greater (p = 0.043) than that in Group 2 (-1.85). Favorable responses on clinical ground occurred in 9 patients (69%) in Group 1 and in 5 patients (38%) in Group 2. The difference was particularly evident on soft tissue changes and extraocular muscle involvement. Severe eye muscle restriction was substantially unaffected by either treatment. In conclusion, the association of orbital irradiation and high dose systemic glucocorticoids in the treatment of severe Graves' ophthalmopathy provides more favorable responses than orbital radiotherapy alone.

Adult↗

PubMedDate not supplied

High-dose intravenous therapy with 7S immunoglobulins in autoimmune endocrine ophthalmopathy.

OBJECTIVE: Endocrine ophthalmopathy is an autoimmune disorder of the retroorbital space tissues which is generally associated with thyroidal Graves' disease. Its pathogenetical aspects, clinical appearance and diagnostic procedures are reviewed. Therapeutic options include both established and more experimental approaches. Increasing use of intravenously administered immunoglobulin preparations has been noted in a variety of autoimmunologically mediated diseases. We report preliminary data of an observational trial on high-dose immunoglobulin treatment including 10 patients suffering from thyroid eye disease. METHODS: Ophthalmopathy which had not been present for longer than 12 month and Graves' disease with an euthyroid metabolic state at the time of the investigation were the inclusion criteria. Therapy was commenced with a high initial immunoglobulin dose of 20 g/d over a period of five days, and 4 further doses of 20 g each were administered at intervals of 4 weeks. RESULTS: No significant decrease was found in the clinical ophthalmopathy index and in thyroid-specific autoantibody levels. The eye muscle index, determined radiologically by orbital computed tomography as a parameter for inflammatory eye muscle involvement, also did not change significantly during therapy. CONCLUSION: In contradiction to previous reports, our results do not at present allow a general recommendation of high-dose immunoglobulin treatment in thyroid-related ophthalmopathy. Immunoglobulin therapy might be effective in selected patients, but criteria for selection have to be defined.

Adult↗

PubMed2004

Muscular bridge between the inferior oblique and inferior rectus muscles.

PURPOSE: In this study, we aimed to investigate the muscular bridge between the inferior oblique (IO) and inferior rectus (IR) muscles of the eye. DESIGN: Cohort study. METHODS: The orbits of sixty intact cadavers with no history of eye muscle or orbital disorders during life were carefully dissected to expose the muscular bridge between the IO and IR muscles. Numbers of the bridges, their length and width were recorded. RESULTS: We observed muscular bridge between IO and IR muscles in 6.6% of 60 orbits. They originated from the lateral side of the IR muscle, and joined to posteromedial side of the IO muscle. Mean length and width were 14.2 +/- 6.3 and 1.3 +/- 0.2 mm, respectively. CONCLUSIONS: Muscular bridges were found in 6.6% of orbits dissected. We conclude that muscular bridges are important due to potential cause of failed IO or IR muscles surgery. In this respect, before surgery of the extraocular muscles, the muscular bridges should be kept in mind and demonstrated by computed tomography or magnetic resonance imaging in transverse, sagittal, and coronal planes.

Adult↗