Aftereffect induced by prisms of different power in the rehabilitation of neglect: A multiple single case report

OBJECTIVES: Prism Adaptation (PA) is a technique used in the rehabilitation of unilateral spatial neglect. Several researchers have reported positive results on a number of tasks, but negative outcomes have also been reported. These conflicting results could be due to the use of prisms of different power. The aim of this study was to investigate the amplitude and duration of the aftereffect induced by prisms of different power by different measures in a series of single cases of neglect. METHODS: Five neglect patients and ten control subjects participated in the study. Prism adaptation was evaluated with Subjective Straight Ahead (SSA), Open-Loop Pointing (OLP) and Line Bisection (LB) tasks, immediately before prism adaptation, immediately after, and 10/60 minutes after prism adaptation. The procedure was repeated with prisms of 5, 10 and 20 prismatic diopters (Δ). RESULTS: The OLP task provided the most sensitive measures for the size of the aftereffect. The 20 Δ prism proved to be most effective in inducing an immediate aftereffect, while the aftereffect of the 5Δ prism seemed to last longer. CONCLUSION: We showed that the prism power and the task used for assessing PA effect are relevant variables to be consider in clinical practice of neglect rehabilitation.