Cyclofusion in normal and superior oblique palsy subjects

Purpose: To evaluate the cyclofusional status in normal and acquired superi or oblique palsy subjects. To know the extent to which cyclodeviations can be tolerated asymptomatically. Method: Incyclovergence and excyclovergence break points and recovery point s were evaluated in 40 normal subjects and 17 cases of acquired superior ob lique 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 wa s spontaneous in 8 cases, and after surgery in 9 cases. Result: The normal values for incyclovergence and excyclovergence were in t he range of 12 degrees (break point) and 8 degrees (recovery point). In the case of superior oblique palsy, only the incyclovergence recovery point wa s 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 norma lized' but the MET did not recover at 1-meter distance fixation. The maximu m torsional tolerance values appear to be more critical. Conclusion: The cyclofusional vergence under physiological conditions are b etter than reported earlier. But MIT and MET are better indicators of cyclo fusional potential. These low values demand more precise alignment of the t orsion in weakening or strengthening surgery of the oblique muscles.