Saccadic visual search training: a treatment for patients with homonymous hemianopia

Abstract

Objectives: We describe a novel rehabilitation tool for patients with homonymous hemianopia based on a visual search (VS) paradigm that is portable, inexpensive, and easy to deploy. We hypothesised that by training patients to improve the efficiency of eye movements made in their blind field their disability would be alleviated. Methods: Twenty nine patients with homonymous visual field defects (HVFD) without neglect practised VS paradigms in 20 daily sessions over one month. Search fields comprising randomly positioned target and distracter elements, differing by a single feature, were displayed for three seconds on a dedicated television monitor in the patients' homes. Improvements were assessed by examining response time (RT), error rates in VS, perimetric visual fields (VFs) and visual search fields (VSFs), before and after treatment. Functional improvements were measured using objective visual tasks which represented activities of daily living (ADL) and a subjective questionnaire. Results: As a group the patients had significantly shorter mean RT in VS after training (p,0.001) and demonstrated a variety of mechanisms to account for this. Improvements were confined to the training period and maintained at follow up. Three patients had significantly longer RT after training. They had high initial error rates which improved with training. Patients performed ADL tasks significantly faster after training and reported significant subjective improvements. There was no concomitant enlargement of the VF, but there was a small but significant enlargement of the VSF. Conclusion: Patients can improve VS with practice. This usually involves shorter RTs, but occasionally a longer RT in a complex speed-accuracy trade-off. These changes translate to improved overall visual function, assessed objectively and subjectively, suggesting that they represent robust training effects. The underlying mechanism may involve the adoption of compensatory eye movement strategies.

Intravenous Thrombolysis in Ischemic Stroke Patients With Isolated Homonymous Hemianopia

“…17 To this end, evaluation of features of scan paths as a base for eye movement strategies was reported. 18 Another example is saccadic visual search training 19 and optokinetic therapy. 20 An obvious limitation of our study is its observational character, ie, we are lacking a control group of untreated hemianopes.…”

Efficacy and Feasibility of Home-Based Training for Individuals With Homonymous Visual Field Defects

“…Even the majority of computer-based training is either completed in clinic 16,17 or at home with therapist supervision 20,22,23 , although one recent study has demonstrated that a web-based reading training can increase reading speed in patients with right-sided HVFDs 27 . Whether it is the patient regards to exploration and reading 22,28 .…”

“…Although few studies have evaluated such therapy relative to a control intervention, several studies have reported significant benefits following compensatory training such as improved exploration, more efficient saccadic behaviour and subjective improvements in activities of daily living (ADL) [16][17][18][19][20][21][22][23] . Specific compensatory reading training has also been developed and positive effects reported [24][25][26] .…”

Inefficient search strategies in simulated hemianopia.

“…One strategy to compensate for a lateralized field deficit is to saccade as far into the blind field as possible to maximise the proportion of the search area that falls in the sighted field (Pambakian, Currie, & Kennard, 2005;Pambakian, Mannan, Hodgson, & Kennard, 2004). Encouraging patients to utilize these strategies in real life improves general functioning (based on selfreports, Mannan, Pambakian, & Kennard, 2010;Zihl, 1981).…”