4.5 Visual Dysfunctions
Dysfunctions of the visual system are quite common following TBI (Morton, 2004). The overall incidence of cranial nerve injury in individuals hospitalized following TBI has been reported to be 19% (Bontke et al., 1993) as cited in (Morton, 2004). It was observed that cranial nerve VII was the most frequently injured (9%), followed by cranial nerves III (6%) and VI (6%) (Bontke et al., 1993) as cited in (Morton, 2004). It is a relatively new concept that the visual system can respond to treatments directed towards the visual-perceptual and/or visual motor skills in individuals with acquired neurological damage. The visual system is highly integrated with many functions other than simply sight, as it also acts as a primary sensory receptor for motor, social, cognitive, communicative, and emotive tasks. Improvements in visual-perceptual and visual-motor disorders can increase function in all the aforementioned areas and can enhance maximal functional recovery. Consequently, it is necessary to direct a fair amount of attention to visual system disorders in individuals with TBI and this aspect should be considered an essential part of any rehabilitation program (Morton, 2004). In a review conducted by Riggs et al. (2007), the authors noted thatvisual rehabilitation studies has primarily involved stroke patients and has largely neglected the TBI population. Their review indicates that visual neglect disorders resulting from a stroke and brain injury show improvement after treatment with prisms, visuomotor feedback training and patching interventions.
INDIVIDUAL STUDIES
Table 4.17 Incidence and Treatment of Visual Dysfunction in Individuals with Brain Injury
| Author/Year/ Country/ Study design/ PEDro & D&B Score |
Methods |
Outcome |
|
Kasten et al., (2000) Germany RCT D&B = 17 PEDro = 9 |
N=32 Subjects (9 vascular disease, 23 ABI) with either optic nerve injury or post-chiasmic injury were randomly assigned to either the restitution group or the control group. The restitution group trained for 1 hour each day at home for at least 150 hours over a 6 month period. Their training program included the Visure program and the SeeTrain program. The control group trained with the placebo for the same amount of time using the FixTrain program. | The restitution group showed an increase in high-resolution campimetry (PeriMa) after training (p<.01) and also in conventional perimetry (TAP-2000) (p<.04). The results also suggest an improvement in pattern recognition (PeriForm 5.6 ± 1.6%, ns) and colour discrimination (PeriColor 6.1 ± 2.1%, ns) within the defective area of the visual field. Correlation between campimetry on the computer screen and conventional TAP perimetry was found to be significant (r=.52, p<.05) suggesting enlargement of visual field size has generalized effects on color recognition and form recognition. Correlation was also found between PeriMa and PeriForm (r=.67, p<.05) and PeriForm and PeriColor (r=.37, p<.05). All tests of visual function (PeriMa, PeriForm, PeriColor) demonstrated a shift of the visual field border in the direction of the blind area for subjects in the restitution group. |
|
Kasten et al., (1998) Germany RCT D&B = 19 PEDro = 9 |
N=38 Subjects (10 stroke, 28 ABI) with either optic nerve injury or post-chiasmic injury were randomly assigned to either the restitution group or the control group. The restitution group completed 150 hours of visual restitution training (VRT) over 6 months at home in a darkened room. The control group completed 150 hours of a fixation training program which required eye movement toward stimuli within the foveal region. | The ability of the subjects in the experimental group to perceive visual stimuli above detection threshold improved after training evidenced by their high-resolution perimetry (HRP) performance (post-chiasmic: p<.05, optic nerve: p<.01). The restitution group demonstrated a higher frequency of response to stimuli than the control group (p<.05). Subjects with optic nerve damage benefitted most from VRT. A border shift was observed for subjects in the restitution group for both types of injury (p<.001). As measured by Tübinger automatic perimeter 2000 (TAP), subjects in the restitution group with optic nerve injury had a decrease in the area of absolute defect (p<.01). 30 of the subjects responded to a follow-up questionnaire, 72.2% of subjects who received VRT reported subjective improvement while only 16.6% of the control subjects did so. (x2=8.89, p<.03). |
|
Doble et al., (2010) USA Pre/post D&B = 14 |
N=43Subjects post TBI with a mean age of 44.4 ± 12.6 years presented with binocular vision dysfunction despite receiving standard treatment and medications. The subjects were asked to complete with Vertical Heterophoria Symptom Questionnaire (VHS-Q) prior to treatment with prismatic lenses and following treatment. The subjects mean duration of treatment was 3.6 months. | On a scale of 0-75, the mean VHS- score at baseline was 34.8 ± 16.1. After prismatic lens treatment, the mean difference in VHS-Q score from baseline was 16.7 ± 12.8 which was significantly different from 0 (p<.01). The subjects reported a mean subjective improvement from baseline of 71.8%. There was a significant correlation between the relative improvement on the VHS-Q and the estimated percentage of improvement (r =.31, p=.04). |
|
Ciuffreda et al.,
(2006) |
N=14 Subjects (9 TBI and 5 stroke) who had difficulty reading participated in oculomotor rehabilitation at least 1 year post-injury involving single-line and multiple-line simulated reading, and basic versional tracking (fixation, saccade, and pursuit) 2x per week for an 8 week period. Training modes included normal internal oculomotor visual feedback in isolation (T1 for 4 weeks) or concurrent with external oculomotor auditory feedback (T2 for 4 weeks). Stimulated reading, Visagraph, basic versional eye movements, and the reading rating scale were used to assess outcomes. |
Significant improvements on each of the five questions on the reading rating scale (p<0.01). Multiple and single line training for the stimulated reading saccade ratio showed significant improvements in both the TI and T2 periods compared to pre-training levels. More improvements were noted in the TBI subgroup for both the stimulated reading and Visagraph. There was a trend (0.05 < p < 0.10) for reading improvement to be greater with the combined visual plus auditory oculomotor feedback. |
|
Padula et al., (1994) USA Case control D&B = 13 |
N=20(10 TBI compared to 10 non-injured). Visual evoked potentials (VEP) were performed using Nicolet Compact Four Electrodiagnostic System and a Visual Stimulator over three trials. During the baseline trial, subjects were tested without bi-nasal occluders and base in prisms. In the experimental trial, subjects were tested with bi-nasal occluders and two diopters of base in prisms. In the last phase, the bi-nasal occluders and prisms were removed and the subjects were re-evaluated. | The use of base-in prisms and bi-nasal occluders produced a large increase in VEP amplitude in the experimental group (p<0.01). There was a significant difference between the change in the experimental group and the change in the control group such that the bi-nasal occluders and base in prisms only improve VEP in subjects who sustained a TBI (p<.01). |
|
Schlageter et al.,
(1993) |
N=51 Brain injured inpatients were evaluated for visual dysfunction. 6 patients underwent several weeks of treatment and were evaluated at 2-week intervals. |
59% of the subjects scored impairments in one or more of the following: pursuits, saccades, ocular posturing, stereopsis, extra-ocular movements, and near far eso-exotropia. 4 of the 6 patients treated for visual impairments showed no improvement in pursuits across the baseline period of time but did show improvement by the final evaluation post treatment. 2 showed no improvement over time. Both pursuits and saccades showed no significant improvement with treatment. |
|
Gianutsos et al.,
(1988) |
N=55 severely brain injured residents of a long-term rehabilitation facility were screened for visual function. Those who were identified as having visual problems underwent treatment with a practitioner or and optometrist. |
36 of the 55 individuals had visual sensory impairments. 26 underwent a rehabilitative optometry program. All who received treatment benefited. |
|
Williams et al., (1995) |
N=1 A 35-year old woman referred to a low vision rehabilitation program because of reading and writing difficulties after a traumatic brain injury was evaluated. |
The treatment resulted in measurable and functional improvements in the client’s ability to read and write. |
PEDro = Physiotherapy Evidence Database rating scale score (Moseley et al. 2002); D&B = Downs and Black (1998) quality assessment scale score.
DISCUSSION
Visual dysfunction post ABI can be corrected with base-in prisms as they affect the ambient visual process by increasing the effectiveness of binocular cortical cells (Padula et al.,1994). Base-in prisms and bi-nasal occluders incorporated within the lenses of both eyes increase the amplitude of visual-evoked potentials (Padula et al., 1994). Vertical heterophoria is also diminished by prismatic lens treatment which reduces the faulty vertical alignment signal generated by the brain injury following TBI (Doble et al., 2010).
Visual restitution training (VRT) completed on a computer monitor with individuals with optic nerve injury or post-chiasmic injury associated with ABI experience visual field enlargement and increased light detection (Kasten et al., 1998). Improvements in visual detection due to detection training result in a transitioning of improvements in other visual functions such as shape and color recognition (Kasten et al., 2000).
When the reading dysfunction post-ABI is a result of sensory-based hemifield deficits or neuromotor deficits, saccadic occulomotor rehabilitation can lead to improvements in eye movements which are required for accurate reading (Cuiffreda et al., 2006). Repetitive occulomotor conditioning reduces the cognitive and attentional load of reading and results in a structural and systematic approach to reading. The benefits of occulomotor rehabilitation were observed in other activities of daily living such as concentration and visual scanning. Most importantly, reducing visual deficits in patients post-TBI may facilitate their involvement in other therapies and contribute to overall recovery (Cuiffreda et al., 2006).
CONCLUSIONS
There is Level 1 evidence to suggest the computer based restitution training is effective in improving the vision of those who sustain a TBI.
There is Level 4 evidence showing that base-in prisms and bi-nasal occluders are effective in treating ambient vision disturbances resulting from an ABI.
There is Level 4 evidence indicating the prismatic spectacle lenses is effective in correcting vertical heterophoria in ABI patients with post-concussive symptoms.
There is Level 4 evidence that rehabilitation programs directed at improving visual function improves functional outcomes such as reading in patients post-ABI.
|
Computer based restitution training has been shown to improve the vision of those who sustain a TBI.
Base-in prisms and bi-nasal occluders has been shown to be effective in treating ambient vision disturbances.
In patients who have been diagnosed with post-concussive symptoms, prismatic spectacle lenses have been shown to be effective in correcting vertical heterophoria.
Rehabilitation programs directed at improving visual function may improve visual functional outcomes post-ABI.
|