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H J Simonsz

Publications and source records attributed to H J Simonsz.

53 records · Page 3Linked to original sources
PubMed1988

Length-tension curves of human eye muscles during succinylcholine-induced contraction.

We have made intraoperative, continuous-registration, length-tension diagrams of detached eye muscles in 80 strabismus patients under general anaesthesia. In 47 of these we repeated the measurements after contraction evoked by succinylcholine chloride. In contracting horizontal and vertical rectus muscles, we found a linear relation between length and tension. In contracting oblique muscles, however, the relation between length and tension was frequently nonlinear. In superior oblique palsies, the superior oblique was found to be stiff after elongation and before injection of succinylcholine, and it did not contract after injection of succinylcholine. The ipsilateral inferior oblique did contract after injection of succinylcholine, but with a higher spring constant than usual (ie, contracture of the ipsilateral antagonist). In three cases the superior oblique contracted vividly after administration of succinylcholine despite the presence of excyclotropia, stereopsis, torticollis (two cases) and a hypertropia that increased in adduction, in down-gaze, in adduction and down-gaze and on ipsilateral head-tilt. In a case of general fibrosis syndrom we found almost normally contracting vertical recti, which is compatible only with a supranuclear or misdirectional cause. These cases demonstrate the usefulness of the assessment of the length-tension diagram of an eye muscle during surgery, before and during contraction evoked by succinylcholine chloride.

Humans↗
PubMed1987

Analysis of the dosage controversy in recess-resect and Faden surgery with the Robinson computer model of eye movements.

In recess-resect surgery, the dosage depends on the preoperative angle of squint and on the ratio between squint-angle reduction and dosage that the surgeon has found in previous surgery. Recommendations pertaining to this ratio vary widely among authors. Some say a recession does more than a resection, while others believe the opposite is true. Finally, most find a lower ratio at smaller preoperative angles of squint. We investigated the matter, using our modified version of the Robinson computer model of eye movements. We calculated the amounts of surgery needed to reduce 10, 15, 20, 25, and 30 degree angles of squint to zero. The increase of the ratio at large angles of squint was indeed predicted by the model. The decrease at small angles of squint, however, was not predicted by the model. We found it impossible to model the decrease of the ratio at small preoperative angles of squint. The ratios for recess and resect surgery were approximately similar. We present an inventory of the possible causes of the discrepancies. In addition, we calculated the effects of Faden surgery and found that the predictions of the computer model correspond closely to reality.

Computers↗
PubMed1986

Intraoperative length and tension curves of human eye muscles. Including stiffness in passive horizontal eye movement in awake volunteers.

Intraoperative continuous-registration length and tension curves of attached and detached eye muscles were made in 18 strabismic patients under general anesthesia. For relaxed eye muscles, we found an exponential relation between length and tension. An increased stiffness was quantified in Duane's syndrome, Graves' disease, orbital-floor fracture, and superior oblique palsy. The stiffnesses of agonist and antagonist were remarkably similar, not only in uncomplicated squint, but also when only one of the two had initially become stiffer. After intravenous administration of succinylcholine chloride, the eye muscles contracted, and the exponential length and tension curve changed into a set of straight, parallel lines. In addition, we measured stiffness in passive horizontal eye movement in awake volunteers and found 0.52 to 1.26 g/degrees (other eye in 5 degrees of adduction), confirming other published results.

Adult↗
PubMed1985

Sideways displacement and curved path of recti eye muscles.

We investigated the sideways displacement of recti muscles with the eye in various gaze-positions by making computed tomographic (CT) scans in a plane perpendicular to the muscle cone, posterior to the globe. We found no consistent sideways displacement of the horizontal recti in the up or down gaze or the vertical recti in the left or right gaze. We found a substantial displacement, however, of the contracting and relaxing muscles. Consequently, we made CT scans in a horizontal plane through medial and lateral recti and found that, with the eye in primary position, the recti muscles follow a curved path. The curvature of the path increased following muscle relaxation and decreased following muscle contraction.

Eye Movements↗
PubMed1985

Bielschowsky head-tilt test--I. Ocular counterrolling and Bielschowsky head-tilt test in 23 cases of superior oblique palsy.

We have measured the amplitude of ocular counterrolling (OCR) and the change in vertical deviation in the Bielschowsky head-tilt test (BHT) in 23 cases of unilateral superior oblique palsy. OCR was measured with a photographical method, using limbal, conjunctival vessels as landmarks. Average OCR of the healthy eye was 5.4 +/- 2.4 (SD) deg either side, at 45 deg of body-tilt. BHT and OCR (of the healthy eye) were not related in the group as a whole. An important perturbing factor was the duration of the palsy. To clarify the relation between BHT, OCR and duration of palsy, the BHT/OCR ratio was calculated in each patient. Six cases with a palsy of presumed recent onset had BHT/OCR ratio of 0.57 +/- 0.09, while twelve cases of long-standing palsy had a BHT/OCR ratio of 1.04 +/- 0.71. This means that in cases of recent onset, the relation was relatively fixed. All high BHT/OCR ratio's occurred in long-standing palsies, whether acquired or congenital. In our opinion, disproportionately large amplitudes in the Bielschowsky head-tilt test are caused by secondary innervational changes or contractures.

Adolescent↗
PubMed1984

Measurement of the mechanical stiffness in cyclotorsion of the human eye.

We have measured the stiffness in cyclotorsion of the human eye using a scleral suction contact ring mounted on a shaft fitted with an eddy current motor to provide the torque to turn the eye and a shaft-position-encoder to register the torsion. The relation proved to be almost linear within the measuring range in four subjects with constant slope values of about 0.75, 0.60, 0.55 and 0.45 g . cm/deg. The average, 0.6 g . cm/deg, equals 0.5 g if applied at the radius of the globe. This value is rather low compared to the values obtained by other authors for horizontal eye movements. This may be due to different length-tension characteristics of oblique muscles compared to recti muscles.

Adult↗
PubMed1982

An orbital fistula complicating anaerobic frontal sinusitis and osteomyelitis.

A patient is described with an orbital fistula complicating frontal sinusitis and osteomyelitis of the frontal bone. The fistula was excised, but a fortnight later an acute exacerbation occurred. From the discharging pus a Staphylococcus aureus was cultured and from mucosa obtained during surgery a microaerophilic Streptococcus. These findings led to the diagnosis: synergistic bacterial inflammation of the frontal sinus, with osteomyelitis and orbital cellulitis.

Adult↗
PubMedDate not supplied

The length-tension diagrams of human oblique muscles in trochlear palsy and strabismus sursoadductorius.

We determined the relation between length and tension in detached oblique muscles of 16 strabismus patients that underwent surgery, before and during contraction evoked by intravenous administration of succinylcholine. We frequently found a nonlinear relation between length and tension, unlike our previous findings in recti. In superior oblique palsies, the superior oblique was found, before injection of succinylcholine, to be stiff after elongation, and did not contract after injection of succinylcholine, while the ipsilateral inferior oblique contract after injection of succinylcholine, but with a higher spring constant than did usual. In 3 cases the superior oblique contracted vividly after administration of succinylcholine despite the presence of excyclotropia, stereopsis, torticollis (2 cases) and a hypertropia that increased in adduction, in downgaze, in adduction-and-downgaze and on ipsilateral head-tilt. The finding of a vividly contracting superior oblique is incompatible with the diagnosis of a complete superior oblique palsy. We conclude that some of the cases diagnosed as congenital superior oblique palsy, having a hypertropia increasing in adduction, in downgaze, in adduction-and-downgaze and on ipsilateral head-tilt, are in fact cases of unilateral strabismus sursoadductorius (upshoot in adduction), a non-paretic motility disorder.

Adolescent↗
PubMedDate not supplied

Phakomatosis pigmentovascularis.

We report a patient with phakomatosis pigmentovascularis IIb and numerous iris hamartomas. Phakomatosis pigmentovascularis IIb is characterized by the simultaneous occurrence of a nevus flammeus, a mongolian spot, and sometimes a nevus anemicus in the same individual, with systemic involvement. To our knowledge, the association with multiple iris hamartomas has been reported only once. This second patient suggests that the association might be more common. Additional reports will indicate if such an association is more frequent than is now assumed.

Child, Preschool↗