Machner B, Könemund I, Sprenger A, von der Gablentz J, and Helmchen C. Randomized Controlled Trial on Hemifield Eye Patching and Optokinetic Stimulation in Acute Spatial Neglect. Stroke. 2014
Hemisensory neglect has a major detrimental impact on stroke recovery, impairing multiple activities of daily living. For this reason, many rehab experts feel that large right MCA strokes are worse than large left MCA strokes from a recovery stand point. Two strategies that demonstrate limited success in treating hemisensory neglect include hemifield eye patching (HEP) and optokinetic stimulation (OKS). HEP is somewhat akin to constraint-induced movement therapy of the limbs – the patient wears glasses that are taped with opaque tape over ½ of both lenses corresponding to the intact visual hemifield. OKS entails using an optokinetic strip to induce smooth pursuit eye movements, thereby correcting the shifted visuospatial midline experienced by these patients. In this article, Machner and colleagues compared a combined approach using HEP + OKS early after stroke to standard rehab in those with large right hemispheric strokes. They found that both groups achieved considerable improvement with no added benefit in the group receiving HEP + OKS.
The authors randomized 21 patients with right hemispheric stroke to one week of HEP + OKS within 14 days of stroke (n=11) vs. standard care (n=10). Study endpoints included a mean score from various tests for neglect, such as the Bell’s cancellation and line bisection tasks. Both the treatment and the control group demonstrated significant improvement on measures of neglect, both immediately after therapy and at one month. There was no significant difference between groups and notably no trends to suggest the study was underpowered.
The negative results of this study are frustrating but it may be premature to give up on HEP and OKS as therapeutic strategies for hemisensory neglect. The authors chose to test these interventions in the early phase after stroke. The rapid recovery that stroke patients achieve naturally during this phase may have washed out any difference between groups. In addition, testing endpoints beyond 30 days, which was not performed, may have shown separation between groups. The authors did an admirable job getting subjects to wear the taped glasses for all waking hours, yet I wonder if taped glasses are truly comparable to constraint-induced therapy of the limbs. For the glasses to be fully effective, the subject must look straight forward at all times. If the subject cheats by looking to the left or right, much of the effect would be lost. Perhaps a better intervention would entail contact lenses darkened on one side to maintain hemifield coverage regardless of the direction of gaze. Despite these minor concerns, this was a well-designed study of HEP + OKS to treat hemisensory neglect. The results suggest that more work is needed to identify an effective therapy for this debilitating condition.