Bagolini glasses: do they affect the horizontal prism fusion amplitude?

Bagolini striated glasses (BSG) can be used while performing the prism fusion amplitude to verify the maintenance of binocularity. The aim of this clinical study was to evaluate whether these glasses affect the prism fusion amplitude.

Fifty-six subjects were examined at the Eye Care Clinic at the University of Applied Sciences Utrecht. The positive and negative prism fusion amplitudes were measured, incorporating the BSG at random, for both near and distance, with right and left eye fixating.

Fifty-two normal subjects with a mean age of 21 years (range 17-28) were recruited. The median prism fusion amplitude at near was 10 BI to 33 BO with the BSG and 13 BI to 38 BO without (p < 0.001). At distance the median amplitude was 8 BI to 33 BO both with and without these glasses (p = 0.104).

Although BSG are useful to verify whether binocularity is maintained, significantly smaller fusional ranges were obtained during measurements at near. In clinical terms, fusional ranges can vary significantly when using the BSG.