Measurement of the mechanical stiffness in cyclotorsion of the human eye

Simonsz, Huibert J.; Crone, Robert A.; Waal, Bob J. de; Schooneman, Martin; Haas, Hendrik A.L. Lorentz de

doi:10.1016/0042-6989(84)90071-3

Cited by 17 publications

(11 citation statements)

References 2 publications

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“…It is a very difficult value to measure in vivo, because rotating the eye after taking the horizontal rectus muscles off, will confer a small translational movement, that mars the measurement. The spring constant of the adnexa is probably slightly less for torsional eye movements as compared to horizontal and vertical eye movements, as we found only 0.50 g/degree, on average, in passive, torsional rotation of the eye in awake volunteers [25][26]. (In the latter experiments, we found a linear relation between rotation and torque in all volunteers.…”

Section: Methodsmentioning

confidence: 67%

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

Simonsz

Dijk

1987

Doc Ophthalmol

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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.

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Section: Methodsmentioning

confidence: 67%

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

Simonsz

Dijk

1987

Doc Ophthalmol

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“…Secondly, the forces exerted by the vertically acting muscles can only be tentative at present. Simonsz et al (1984) have queried the validity of the description of the length -tension curves of the obliques, because the model predicts greater stiffness than is actually found during passive cyclo-rotation of the eye.…”

Section: Discussionmentioning

confidence: 99%

Excursion Tests of Ocular Motility

Boylan

Clement

1987

Ophthalmic Physiologic Optic

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Three alternative excursion tests of ocular motility have been compared. A computer model of the mechanics of the extraocular muscles has been used to estimate the tensions developed by the muscles in these tests. On the basis of these calculations we recommend the transverse test in which the positions of the eyes are observed as they track a target moving from the right to the left with a fixed elevation and a fixed depression.

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“…In short, a length and tension measuring device [6] was fixed during surgery rigidly above the head of the patient. It consisted of a 2 mm hardened steel shaft, suspended by precision microballbearings and equipped with a shaft-position encoder and an eddy-current motor.…”

Section: Methodsmentioning

confidence: 99%

Increased muscle tension and reduced elasticity of affected muscles in recent-onset Graves' disease caused primarily by active muscle contraction

Simonsz

Kommerell

1989

Doc Ophthalmol

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Abstract. In 3 patients with Graves' disease of recent onset, length-tension diagrams were made during surgery for squint under eyedrop anesthesia. The affected muscles were found to be very stiff when the other eye looked straight ahead. It was expected that these stiff muscles would be able to shorten to some extent but would be unable to lengthen, due to fibrosis of the muscle. We found that the affected muscles did not shorten very much when the other eye looked into the field of action of the muscle. Unexpectedly however, they lengthenend considerably when the other eye looked out of the field of action of the muscle. This finding implies that the raised muscle tension and reduced elasticity of affected muscles in these cases of Graves' disease of recent onset were primarily caused by active muscle contraction, not by fibrosis.

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Measurement of the mechanical stiffness in cyclotorsion of the human eye

Cited by 17 publications

References 2 publications

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

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

Excursion Tests of Ocular Motility

Increased muscle tension and reduced elasticity of affected muscles in recent-onset Graves' disease caused primarily by active muscle contraction

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