TY - JOUR
T1 - Quantitative forced ductions in an animal model - Characterization of passive forces
AU - Brooks, Steven E.
AU - Yu, Jack C.
AU - Preston, Dean
AU - Johnson, Maribeth
N1 - Funding Information:
From the Departments of Ophthalmology a and Pediatrics, b the Section of Plastic Surgery, Department of Surgery, c and the OJfices of Biomedical Engineering i and Biostatistics, e Medical College of Georgia, Augusta, Georgia. Supported by an unrestricted departmental award from Research to Prevent Blindness, Inc. (S.E.B.), the Knights Templar Educational Foundation of Georgia (S.E.B.), and the American Sodety of Maxillofadal Surgeons (~. C. Y.). Submitted November 11, 199Z Revision accepted February 2, 1998. Reprint requests: Steven E. Brooks, MD, Department of Ophthalmology, Medical College of Georgia, 1120 l Yth St, Augusta, GA 30912. Copyright © 1998 by the American Association for Pediatric Opbthahnology and Strabismus. 1091-8531/98 $5.00 + 0 7~/I/91568
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 1998
Y1 - 1998
N2 - Purpose: Our purpose was to characterize the passive tissue forces involved in ocular rotation in a controlled animal model and to evaluate the influence of manual versus mechanized ductions, repeated measurements, speed of rotation, and the influence of the nondepolarizing muscle relaxant mivacurium. Methods: Forced ductions were performed under general anesthesia on 20 eyes of 10 pigs, with or without mivacurium, with use of a highly sensitive force gauge attached to the eye by a traction suture. The eye was moved either manually or at constant speed with a motorized platform. Eyes were rotated a total of 8 mm from their resting position under anesthesia. The force-displacement relationship was analyzed and compared between groups. Results: A linear (elastic) relationship between force and displacement was noted, with a slope of 0.4 g per degree with use of the mechanized technique. Neither speed of rotation, use of mivacurium, nor repeated ductions significantly influenced the shape or slope of the relationship. Hysteresis averaged 2 to 4 g. Measurements performed with use of the motorized platform showed significantly improved reliability over those made manually. Conclusions: The passive length-tension data correlate well with data reported by others in humans. Within a wide range of eye movement, this force is elastic in nature. For relatively low angular velocities, such as might be produced in smooth pursuit, the passive forces do not change appreciably with changes in velocity. The nondepolarizing muscle relaxant mivacurium has no effect on accurate performance of passive forced ductions under general anesthesia. Studies collecting quantitative data on passive orbital forces should be performed, when feasible, with an automated duction and recording apparatus.
AB - Purpose: Our purpose was to characterize the passive tissue forces involved in ocular rotation in a controlled animal model and to evaluate the influence of manual versus mechanized ductions, repeated measurements, speed of rotation, and the influence of the nondepolarizing muscle relaxant mivacurium. Methods: Forced ductions were performed under general anesthesia on 20 eyes of 10 pigs, with or without mivacurium, with use of a highly sensitive force gauge attached to the eye by a traction suture. The eye was moved either manually or at constant speed with a motorized platform. Eyes were rotated a total of 8 mm from their resting position under anesthesia. The force-displacement relationship was analyzed and compared between groups. Results: A linear (elastic) relationship between force and displacement was noted, with a slope of 0.4 g per degree with use of the mechanized technique. Neither speed of rotation, use of mivacurium, nor repeated ductions significantly influenced the shape or slope of the relationship. Hysteresis averaged 2 to 4 g. Measurements performed with use of the motorized platform showed significantly improved reliability over those made manually. Conclusions: The passive length-tension data correlate well with data reported by others in humans. Within a wide range of eye movement, this force is elastic in nature. For relatively low angular velocities, such as might be produced in smooth pursuit, the passive forces do not change appreciably with changes in velocity. The nondepolarizing muscle relaxant mivacurium has no effect on accurate performance of passive forced ductions under general anesthesia. Studies collecting quantitative data on passive orbital forces should be performed, when feasible, with an automated duction and recording apparatus.
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U2 - 10.1016/S1091-8531(98)90059-3
DO - 10.1016/S1091-8531(98)90059-3
M3 - Article
C2 - 10532743
AN - SCOPUS:0032130940
SN - 1091-8531
VL - 2
SP - 239
EP - 245
JO - Journal of AAPOS
JF - Journal of AAPOS
IS - 4
ER -