The Effect of Peripheral Fusion on the 4Δ Test

Judith Sparke, AssocDipO(Cumb), DOBA

Fifty subjects were examined to assess whether peripheral fusion effects the response to the 4Δ test to determine the presence of a central scotoma. The test was performed both with and without peripheral fusion stimuli. It was found that in 23% of cases with a significant heterophoria, or a small angle squint, the presence of a scotoma was only demonstrable when peripheral fusion is eliminated. In the light of the results it is suggested that the usual method of performing the test be modified.