Utility of a cheiroscope to test for simultaneous perception and sensory fusion

The synoptophore has been used clinically to assess simultaneous perception and sensory fusion in strabismic patients; however, due to suppression or the visual condition of patients with normal stereopsis, a synoptophore does not always detect simultaneous perception or sensory fusion. A cheiroscope may be a better alternative.

The aim of this work was ro determine whether a cheiroscope could be useful for examining simultaneous perception and sensory fusion in strabismus patients.

Thirty-three patients with strabismus who could undergo cheiroscopic tracing were categorised into two groups: the intermittent exotropia group (XT; n = 19; mean age 9.8 ± 5.6 yrs, range 5-23 yrs) and the esotropia group (ET; n = 14; mean age 10.2 ± 6.0 yrs, range 4-23 yrs). Two sizes of square line drawings (20° and 6°) were used for the cheiroscopic tracing. The cheiroscopic tracing results were compared with those of synoptophore testing for simultaneous perception and sensory fusion.

The rate of cheiroscopic tracing of detecting sensory fusion was significantly higher than that of the synoptophore. With the synoptophore, simultaneous perception was detected in 89.5% and 85.7% of the XT and ET patients, and sensory fusion was detected in 73.7% and 71.4%, respectively. The synoptophore identified 11 patients who had no simultaneous perception or sensory fusion. Among them, eight patients were associated with suppression and two patients were 4 years old.

Cheiroscopic tracing is useful for determining the presence of simultaneous perception and sensory fusion if they are not detected by a synoptophore due to age < 5 years or suppression.