Does fixation light intensity influence the results from the Sbisa bar when measuring sensory fusion?

Abstract

Aim: To determine whether the level of sensory fusion in normal participants is affected significantly by fixation light intensity. Methods: Seventeen normal adult participants had sensory fusion measurements taken using the Sbisa bar, combined with Bagolini glasses, as a control for binocular single vision, whilst fixating lights of three different intensities: 150 lux, 250 lux and 350 lux. Data were analysed using Friedman's test and the Wilcoxon matched pairs signed ranks test.Results: Seventeen participants were tested (mean 35.3 years, range 23-60 years). Friedman's test showed at least two of the light intensities had a statistically significant effect upon sensory fusion results ( p ¼ 0.011). Wilcoxon matched pairs signed rank testing found no statistically significant difference in levels of sensory fusion when fixating the 150 lux and 250 lux fixation lights ( p ¼ 0.194). There was a statistically significant difference in the level of sensory fusion when fixating the 150 lux and 350 lux lights ( p ¼ 0.011) and the 250 lux and 350 lux lights ( p ¼ 0.017). Conclusion: Changing the intensity of the fixation light from 150 lux to 350 lux and from 250 lux to 350 lux significantly affected the level of sensory fusion measured. The higher the intensity of the light, the greater the filter needed to break fusion. The clinical significance of these results is considered.

Maintenance of normal fusion in intermittent exotropia

“…In the existing literature, the Bagolini filter bar procedure has most often been used to evaluate patients with either constant strabismus 42,43 or normal binocular vision. 40,44,45 Although the method is similar under both conditions (i.e., increasing filter density from the lightest to the heaviest), the issue being studied is different. For a patient with constant strabismus, the initial response is typically suppression or fusion with harmonious abnormal retinal correspondence.…”

“…1). A penlight (1767 lux, measured at 6.5 cm from the light source 40 ) was positioned 5 m from the participant’s eyes. The participant was instructed to look naturally at the fixation light.…”

“…1). A penlight (1767 lux, measured at 6.5 cm from the light source 40 ) was positioned 5 m from For example, if a participant reported fusion (normal retinal correspondence) only at the 1 st , 2 nd and 5 th filters, his/ her fusion maintenance score was 3. The score ranged from 0 to 16, and a higher fusion maintenance score suggests a better ability to maintain normal sensorimotor fusion.…”