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At least 235 records · Page 13Linked to original sources
PubMed1988

The contractile properties and movement dynamics of pigeon eye muscle.

The lateral rectus (LR) muscle of the pigeon was directly stimulated in situ at 41 degrees C. The length tension relationships for active and passive tension were investigated to determine the optimum muscle length (Lo). Isometric responses to single and twin pulses, tetani and sinusoidal stimulation were measured. A linear relationship was found between length and active tension during stimulation. Increase in stimulation frequency produced a corresponding shift in tension with the slope of the curves remaining the same. At Lo (1.21 times resting length) the average contraction time of single twitches was 6.03 ms and the half-relaxation time was 7.77 ms. Stimulation frequencies of 200 Hz and over gave rise to a fused tetanus. Tension increased to a maximum at 200 Hz and rate of tension rise saturated at 600 Hz. The tension response to tetanic stimulation was linear over the range 70-180 Hz. Maximum tetanic tension was around 3.48 N/cm2 and the twitch:tetanus ratio was 0.164. Prolonged activation at fusion frequency showed a high fatigue resistance. Sinusoidal stimulation with pulse trains of 100-180 Hz produced a sinusoidal response over the frequency range 0.6-40 Hz, from which the gain and phase relationships were determined. The muscle response approximates a first order low pass filter, with a characteristic frequency of 11.2 Hz. There is an additional phase lag, equivalent to the response latency, of 2.89 ms. The results are compared to the contractile properties of mammalian eye and avian skeletal muscle. The frequency response of the LR is compared to that of cat soleus and gastrocnemius and to pigeon eye movement dynamics.

Animals↗
PubMed1986

The effect of anticholinergic drugs on the inner eye muscles.

Using 12 healthy volunteers, we tested the para-sympatholytic effects on the eye. In a randomized crossover double-blind trial, hyoscine-N-butylbromide was tested against saline. Before (20 or 40 mg IV) and up to 45 min after the injection, pupillar light reaction, accommodation, visual acuity, and nyctometer values were measured. The range of accommodation diminishes according to dosage: 9-15 min after the injection, the inhibition is maximum; 45 min after the injection, only a small effect remains, even using the 40 mg dosage. Pupillary reaction is little affected by either dosage, and the pupil diameters at the end of the reaction are only slightly greater after the injection of either dosage than after placebo injection. The time constant of the reaction remains unchanged. Visual acuity and nyctometer values remain unchanged under the influence of hyoscine-N-butylbromide. The results are discussed with respect to the potential ability of a patient to meet the requirements of modern traffic. According to our findings, there are no ophthalmologically-based reasons for an emmetropic person to assume impaired driving abilities after a single injection of hyoscine-N-butylbromide of up to 40 mg. If the accommodative capacity of a patient is impaired whose hyperopia is not fully corrected, the ability to drive in modern traffic may be impaired. After a single dose of 20 mg hyoscine-N-butylbromide (i.e., 1 ampule Buscopan), the impairment of even these patients does not last longer than about 45 min.

Accommodation, Ocular↗
PubMed1978

Prenuclear paresis of homolateral inferior rectus and contralateral superior oblique eye muscles.

In a case of left inferior rectus paresis, it is demonstrated that the lesion must be prenuclear. On downward gaze, the left eye, although it reached the required target with a rapid saccade, drifted back towards the midline immediately afterwards. During the drift, several corrective saccades appeared. A dissociated "gaze paretic" nystagmus resulted. Synchronously, the right eye showed an incyclorotary nystagmus. We suspect a lesion of "tonic" fibers supplying the nuclear region of the left inferior rectus and the right superior oblique muscle.

Adult↗
PubMed1984

The structure of the external rectus eye muscles of the carpet shark Cephaloscyllium isabella.

The external rectus muscles of the carpet shark Cephaloscyllium isabella contain two types of muscle fibre. A core of large white fibres which have regular myofibrils with extensive sarcoplasmic reticulum, triads located at the Z disc and a pronounced H band and M line. Mitochondria are frequent but tend to be smaller and less abundant than mitochondria of the smaller red fibre type. The red fibres which surround the central region are rich in mitochondria, have little sarcoplasmic reticulum and triads which are infrequent and dispersed. Sarcomere banding of red fibres is characterised by a faint H band and M line while the Z disc is thick in comparison with that found on the white muscle fibre sarcomere.

Animals↗
PubMed1999

Measurement of recti eye muscle paths by magnetic resonance imaging in highly myopic and normal subjects.

PURPOSE: To analyze the path of extraocular muscles (EOMs) quantitatively in highly myopic subjects with and without restricted eye motility versus control. To elucidate the cause of the acquired motility disorder in patients with high myopia. METHODS: Thirty-three orbits were imaged using a Magnetom or Siemens Vision (Siemens, Erlangen, Germany; both 1.5 Tesla) MRI (magnetic resonance imaging) scanner. Coronal T1-weighted, spin-echo images were obtained with repetition time of 550 msec and echo time of 15 msec. Subjects had to fixate in different positions of gaze. Orbits of three patient groups were analyzed: group 1 (n = 14), patients with high axial myopia and restricted eye motility (average axial length, 31.4 mm; refractive error more than -15 D); group 2 (n = 8), subjects with high axial myopia and normal eye motility (average axial length, 29.2 mm); control group (n = 11), emmetropic subjects with normal eye motility (average axial length, 23.6 mm). RESULTS: Highly myopic patients showed significant displacements of recti EOMs in comparison with control subjects. Mean displacements, measured in the plane 3 mm anterior to the globeoptic nerve junction in primary gaze, were in group 1, lateral rectus (LR) 2.9 mm (2.5 downward, 1.4 medial), medial rectus (MR) 1.3 mm downward and in group 2, LR 1.4 mm (1.3 downward, 0.6 medial) and MR 1.2 mm downward. In groups 1 and 2 the inferior rectus (IR) was displaced 1.3 mm medially and upward. In both groups of myopic patients the superior rectus (SR) was displaced 1.5 mm medially and downward. CONCLUSIONS: In patients with high axial myopia, displacements of all recti EOMs can be detected by MRI. Displacements of SR, MR, and IR were very similar in groups 1 and 2 versus control. LR displacement into the lateral and inferior quadrant of the orbit was greatest in patients with restricted eye motility. Thus, LR displacement is probably the major pathophysiological factor for the restrictive motility disorder in high myopia. EOM dislocations can be explained by myopia-associated alterations in the orbital connective tissues confining EOM positions in relation to the orbital wall.

Adult↗
PubMed1994

[Synkinesia of the internal eye muscles in congenital third nerve paralysis].

Synkinetic lid and ocular movements after traumatic or non-traumatic, acquired oculomotor palsy are well known. Less often misdirection in the intraocular muscles is observed. A 20-year-old female patient suffered from congenital palsy of the third nerve of the left dominant eye. She had residual small-angle exotropia after having extraocular muscle surgery four times during childhood, e.g., after high-dosage recess-resect procedures on the horizontal recti of her left eye. There was an anisocoria with a miotic pupil in the left eye when fixating in the primary position and when attempting right gaze. The patient complained of blurred vision at far fixation in the primary position. Her visual acuity was 0.8 in the primary position and 1.25 in 7 degrees left gaze. Retinoscopy of the left eye revealed a 1-1.25 myopic increase for the primary position. Surgical and non-surgical treatment (e.g., cycloplegia plus bifocal glasses, induced change of the leading eye) is discussed.

Adult↗