Intraoperative length and tension curves of human eye muscles. Including stiffness in passive horizontal eye movement in awake volunteers
H. J. Simonsz, G. H. Kolling, H. Kaufman and B. van Dijk
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.
