title: Isometric force measured in human horizontal eye muscles attached to or detached from the globe.
abstract: BACKGROUND
  Human eye muscle tension has been measured directly only in detached condition. The purpose of this study is to compare force development in single, horizontal human eye muscle during saccadic eye movements, first when the muscle was still attached and later when it was detached from the globe.
  
  
  METHODS
  Eleven horizontal muscles of eight patients were examined during surgery under topical anesthesia for concomitant strabismus. None of the muscles examined had been operated before. Isometric muscle tension was recorded with a strain gauge system, to which the muscle tendon was attached by a silk suture. The subjects made saccadic eye movements with the non-recorded eye by fixating light-emitting diodes in the center and at 10, 20, and 30 degrees horizontally to each side. Continuous and stepwise saccades were produced. In the tension signals, peak tension (Fp), steady tension (Fs), and the ratio Fp/Fs were measured. Statistical analysis was done with multivariate analysis of variance.
  
  
  RESULTS
  The values of Fp, Fs, and Fp/Fs at different amplitudes of the saccadic eye movements were compared in the attached and the detached muscle. There were no consistent statistical differences between the values obtained in the two conditions.
  
  
  CONCLUSIONS
  The muscle force development, measured at the tendon, was the same in muscles attached to the globe and in muscles free from the globe. Thus isometric muscle tension can be adequately recorded in muscles still attached to the globe, which increases the possibilities for studying contractile properties of various eye muscles during ophthalmic surgery procedures performed under topical anesthesia.
authors.affiliation: Department of Ophthalmology, Karolinska Institutet, St Erik's Eye Hospital, The Bernadotte Laboratories, 112 82, Stockholm, Sweden. gunnar.lennerstrand@ste.ki.se
authors.forename: Gunnar
authors.initials: G
authors.lastname: Lennerstrand
authors.forename: Costantino
authors.initials: C
authors.lastname: Schiavi
authors.forename: Suna
authors.initials: S
authors.lastname: Tian
authors.forename: Mariagrazia
authors.initials: M
authors.lastname: Benassi
authors.forename: Emilio C
authors.initials: EC
authors.lastname: Campos
mesh_terms: D000328:Adult; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009799:Ocular Physiological Phenomena; D009801:Oculomotor Muscles / Q000502:physiology* / Q000601:surgery; D009915:Orbit / Q000502:physiology*; D012438:Saccades / Q000502:physiology; D013285:Strabismus / Q000601:surgery