Eye-movement training-induced changes of visual field representation in patients with post-stroke hemianopia

Abstract

Changes in neuronal activity have been described in patients with hemianopia following ischemic lesions of the visual cortex. This reorganization may facilitate compensation of lost visual function that is rarely fully restituted. Improving exploratory eye movements with appropriate training has been shown to partially compensate for the visuoperceptive impairment during daily life activities. The changes in cortical processing of visual stimuli that may be induced by these training strategies, however, are less well described. We used fMRI to study the training effects of eye-movement training on cortical representation of visual hemifields. Brain activation during hemifield stimulation was measured in eight patients with an occipital cortical lesion of the striate cortex causing homonymous hemianopia. Starting 8 weeks after the stroke, patients received 4 weeks of eye movement training. fMRI measurements were performed at baseline and after training. In five patients, follow-up fMRI was performed 4 weeks after the end of training. Differences in activation between rest and hemifield stimulation as well as before and after training were assessed with statistical parametric mapping. Twelve healthy subjects were scanned twice at a 4-week interval. During stimulation of the affected hemifield, significant activation at baseline was found bilaterally in extrastriate cortical areas, with the strongest increases in the contralesional hemisphere. This activation pattern was maintained after training. Four weeks after the end of training, there was an additional activation of the extrastriate cortex in the contralesional hemisphere compared to baseline. No changes in the size of visual field defects were found. In this group of patients, eye-movement training induced altered brain activation in the unaffected extrastriate cortex.

Remaining Visual Field and Preserved Subjective Visual Functioning Prevent Mental Distress in Patients with Visual Field Defects

“…Since the minimum lesion age in these studies was 6 months and none of our patients received visual rehabilitation prior to data acquisition we could not investigate the potential effect of (early) rehabilitation onset on preservation of vrQoL which is also an issue for future research. In fact, neuropsychological training to reduce the visual field defect (Vision Restoration Training, e.g., Sabel et al, 2011b) or to improve visual scanning behavior in the area of partial blindness (eye movement training, e.g., Nelles et al, 2010) are well known. It has not been studied yet if patients with optic neuropathies develop compensatory strategies on their own or receive other advice from low vision services or eye specialists that may transfer into effective coping strategies in everyday life and support to maintain vrQoL and mental health.…”

Mechanisms compensating for visual field restriction in adolescents with damage to the retro-geniculate visual system

“…He has developed an effective ability to scan, of which he is aware. One may speculate that his excellent performance in everyday life and as an elite player on the soccer field may be a consequence of scanning or of motion detection in the blind field 9,10 or both. Subjects 2 and 3 both display a scanning eye movement pattern, which does not resemble the inappropriate saccadic intrusions often seen in patients with cerebellar disorders.…”

“…8 Motion detection in the blind field has also been described in adults with acquired hemianopia. 9,10 With such compensation mechanisms, we can expect that the practical binocular VF function in everyday living differs from the monocular VF function assessed under strict control of fixation.…”

Adaptation to poststroke visual field loss: A systematic review

“…The majority of studies relating to compensatory treatments are concerned with the improvement of eye movements and scanning into the affected field (Bergsma et al., 2011; Roth et al., 2009; Aimola et al., 2014; Hazelton, Pollock, Walsh, & Brady, 2015; Jacquin‐Courtois, Bays, Salemme, Leff, & Husain, 2013; Lane, Smith, Ellison, & Schenk, 2010; Pambakian, Mannan, Hodgson, & Kennard, 2004; Kerkhoff, Münssinger, & Meier, 1994; Mazer et al., 2003; Nelles et al., 2010; Taylor, Poland, Harrison, & Stephenson, 2011; Schuett, Heywood, Kentridge, Dauner, & Zihl, 2012), as well as increased saccadic movements into the affected field (Mannan, Pambakian, & Kennard, 2010; Lévy‐Bencheton et al., 2016; Kerkhoff, Münßinger, Eberle‐strauss, & Stögerer, 1992). A number of studies have specifically reported on subjective improvements in activities of daily living following compensatory therapy, such as improvements in mobility, reading, driving, and detection of obstacles (Bergsma et al., 2011; Ong et al., 2015; Keller & Lefin‐Rank, 2010; Aimola et al., 2014; Jacquin‐Courtois et al., 2013; Kerkhoff et al., 1994; Mazer et al., 2003; de Haan, Melis‐Dankers, Brouwer, Tucha, & Heutink, 2015; Hayes, Chen, Clarke, & Thompson, 2012; Nelles et al., 2001; Rowe, Conroy, et al., 2016).…”