title: Cyclofusion in normal and superior oblique palsy subjects.
abstract: OBJECTIVE
  To evaluate the cyclofusional status in normal and acquired superior oblique palsy subjects. To know the extent to which cyclodeviations can be tolerated asymptomatically.
  
  
  METHODS
  Incyclovergence and excyclovergence break points and recovery points were evaluated in 40 normal subjects and 17 cases of acquired superior oblique palsy. A Polaroid dissociation stereoprojector was used with special torsional slides at fixation distances of 1 meter and 6 meters. In addition, maximum intorsion tolerated (MIT) and maximum extorsion tolerated (MET), ie, the torsion that allowed baseline horizontal fusion, were studied. The evaluation was repeated in the palsy group 1 month after recovery, which was spontaneous in 8 cases, and after surgery in 9 cases.
  
  
  RESULTS
  The normal values for incyclovergence and excyclovergence were in the range of 12 degrees (break point) and 8 degrees (recovery point). In the case of superior oblique palsy, only the incyclovergence recovery point was significantly diminished (p=.004), which improved after recovery to near normal values. The intorsion tolerance (MIT) and extorsion tolerance (MET) also showed deterioration in the palsy group. After recovery, the MIT normalized but the MET did not recover at 1-meter distance fixation. The maximum torsional tolerance values appear to be more critical.
  
  
  CONCLUSIONS
  The cyclofusional vergence under physiological conditions are better than reported earlier. But MIT and MET are better indicators of cyclofusional potential. These low values demand more precise alignment of the torsion in weakening or strengthening surgery of the oblique muscles.
authors.affiliation: Dr. R.P. Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi.
authors.forename: P
authors.initials: P
authors.lastname: Sharma
authors.forename: K
authors.initials: K
authors.lastname: Prasad
authors.forename: S
authors.initials: S
authors.lastname: Khokhar
mesh_terms: D005133:Eye Movements; D006801:Humans; D009801:Oculomotor Muscles / Q000294:innervation / Q000503:physiopathology* / Q000601:surgery; D013508:Ophthalmologic Surgical Procedures; D009886:Ophthalmoplegia / Q000503:physiopathology* / Q000601:surgery; D020432:Trochlear Nerve Diseases / Q000503:physiopathology* / Q000601:surgery; D015357:Vision Disparity / Q000502:physiology*; D015348:Vision, Binocular / Q000502:physiology*