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A recent retrospective study shows that Vision Restoration Therapy (VRT) leads to subjective improvements of vision-guided activities in everyday life. Even patients with small visual field enlargements noted subjective improvements in daily life. Subjective benefits identified include walking/mobility, confidence/independence, reading, hobbies/watching TV.
Abstract
Patients with visual field deficits following stroke or neurotrauma can use vision restoration therapy (VRT) to increase their visual field size by about 5° of visual angle. However, little is known about whether such visual field enlargements are relevant to visually guided activities of daily life. Specifically, we wish to know (1) if VRT affects activities of daily life (ADL) measures, and (2) to what extent any subjective changes correlate with quantitative measures of visual field enlargements.
A retrospective analysis was carried out with data of 69 patients that had been interviewed after 6 months of VRT. Patient testimonials were analyzed post hoc and correlated with demographic status and pre/post VRT changes as measured by perimetric testing. As previously described, VRT significantly increased detection ability and most patients (88%) reported subjective benefits in ADL. A correlation analysis of quantitative parameters of visual field enlargements with subjective patient testimonials was performed. Significant correlation was found in the categories "carrying out hobbies" (r = 0.360) and for "general improvement of vision" (r = 0.244). A trend was evident for the category "reading" (r = 0.215).
No correlation was found between visual field size improvements and "visual confidence/mobility" and "ability to avoid collisions." Thus, visual field size appears only to be one, surprisingly minor, factor among others (such as temporal processing) determining subjective vision in brain damaged patients.
The aim of the study was to examine if improvements of stimulus detection performance in visual field tests after intensive visual training of the visual field border zone in patients with visual field defects are associated with changes in self-reported vision- and health-related quality of life.
Abstract.
Purpose: The aim of the study was to examine if improvements of stimulus detection performance in visual field tests after intensive visual training of the visual field border zone in patients with visual field defects are associated with changes in self-reported vision- and health-related quality of life (QoL).
Methods: We studied a clinical sample of 85 patients suffering from visual field loss after brain damage that underwent repetitive, daily light stimulation (vision restoration training, VRT) of the visual field border and the blind visual field for up to 75 hrs (N =16) or 150 hrs (N = 69). Stimulus detection was quantified in the central visual field with a campimetric method before and after intervention. Health-related QoL was assessed by the Health-Survey SF-36 and vision-related QoL by the 39-item National Eye Institute Visual Function Questionnaire (NEI-VFQ).
Results: Both vision- and health-related QoL measures improved after VRT. Significant increases were found in 8 out of 12 NEI-VFQ and 3 out of 8 SF-36 subscales. Of the 85 participants 6% showed a decrease in stimulus detection performance, 42% showed an increase of less than 5% detected stimuli, 24% showed an increase of 5–10% detected stimuli and 28% of more than 10% detected stimuli. Changes in campimetric stimulus detection rates were related to NEI-VFQ subscales point differences general vision (3 points), difficulty with near vision activities (4 points), limitations in social functioning due to vision (4 points) and driving problems (12 points). There was no relation of visual field changes to changes in SF-36 component and subscale scores.
Conclusions: The NEI-VFQ is a valuable measure of self-reported visual impairment in patients with visual field defects. Stimulation of the visual field by training may lead to improvements of vision-related QoL which were correlated with the extent of visual field enlargements.
Objective’ visual field topography (perimetry) in 19 patients with postgeniculate visual system lesions and related this to the subjective scotoma representation as expressed by patients’ drawings of the defect and monitored changes of these measures during training-induced recovery of function.
Abstract
The cognitive representation of blind regions varies considerably between patients with vision loss and may influence compensatory behaviour and treatment motivation. We therefore measured ‘objective’’ visual field topography (perimetry) in 19 patients with postgeniculate visual system lesions and related this to the subjective scotoma representation as expressed by patients’ drawings of the defect and monitored changes of these measures during training-induced recovery of function. Blind regions were mostly adequately represented; however, central regions were overestimated and peripheral areas underestimated in size. Perimetric and subjective defect size decreased significantly during training. Again, training-induced visual field border shifts in central regions were larger in subjective than in perimetric maps but vice versa in the peripheral field. Thus, vision restoration therapy improves ‘‘objective’’ visual field size along with its cognitive representation. The subjective topography is shaped by the functional importance of visual field regions and is a function of cortical magnification, thus resembling the neural representation in visual cortex.
It has been argued that patients with visual field defects compensate for their deficit by making more frequent eye movements toward the hemianopic field and that visual field enlargements found after vision restoration therapy (VRT) may be an artefact of such eye movements. In order to determine if this was correct, we recorded eye movements in hemianopic subjects before and after VRT.
Abstract
Aim: It has been argued that patients with visual field defects compensate for their deficit by making more frequent eye movements toward the hemianopic field and that visual field enlargements found after vision restoration therapy (VRT) may be an artefact of such eye movements. In order to determine if this was correct, we recorded eye movements in hemianopic subjects before and after VRT.
Methods: Visual fields were measured in subjects with homonymous visual field defects (n = 15) caused by trauma, cerebral ischemia or haemorrhage (lesion age >6 months). Visual field charts were plotted using both high-resolution perimetry (HRP) and conventional perimetry before and after a 3-month period of VRT, with eye movements being recorded with a 2D-eye tracker. This permitted quantification of eye positions and measurements of deviation from fixation.
Results: VRT lead to significant visual field enlargements as indicated by an increase of stimulus detection of 3.8% when tested using HRP and about 2.2% (OD) and 3.5% (OS) fewer misses with conventional perimetry. Eye movements were expressed as the standard deviations (S.D.) of the eye position recordings from fixation. Before VRT, the S.D. was ±0.82◦ horizontally and ±1.16◦ vertically; after VRT, it was ±0.68◦ and ±1.39◦, respectively. A cluster analysis of the horizontal eye movements before VRT showed three types of subjects with (i) small (n = 7), (ii) medium (n = 7) or (iii) large fixation instability (n = 1). Saccades were directed equally to the right or the left side; i.e., with no preference toward the blind hemifield. After VRT, many subjects showed a smaller variability of horizontal eye movements. Before VRT, 81.6% of the recorded eye positions were found within a range of 1◦ horizontally from fixation, whereas after VRT, 88.3% were within that range. In the 2◦ range, we found
94.8% before and 98.9% after VRT. Subjects moved their eyes 5◦ or more 0.3% of the time before VRT versus 0.1% after VRT. Thus, in this study, subjects with homonymous visual field defects who were attempting to fixate a central target while their fields were being plotted, typically showed brief horizontal shifts with no preference toward or away from the blind hemifield. These eye movements were usually less than 1◦ from fixation. Large saccades toward the blind field after VRT were very rare.
Conclusion: VRT has no effect on either the direction or the amplitude of horizontal eye movements during visual field testing. These results
argue against the theory that the visual field enlargements are artefacts induced by eye movements.
