The effect of spectral filters on reading speed and accuracy following stroke

UK exceptional case driving application outcomes in post-stroke homonymous hemianopia: results from a clinical study

PURPOSE

We report results in relation to returning to driving in the UK under the exceptional cases rule for visual field loss.

METHODS

The Hemianopia Adaptation Study is a prospective clinical study recruiting adult stroke survivors with new onset homonymous hemianopia. The mobility assessment course (MAC) was used to measure navigational scanning. Car drivers were offered a 1-year post-stroke assessment to consider referral for driving assessment.

RESULTS

Of 144 participants, 51 were eligible for driving assessment, with 13 (25.4%) accepting appointment for UK Driving and Vehicle Licensing Agency (DVLA) referral. A statistically significant difference in gender and baseline Barthel (stroke severity) scores was found between those requesting referral and those declining (p = 0.046; p < 0.001). MAC outcomes were significantly different, with those referred having a lower percentage of target omissions (9.0%) and faster mean course completion time (46.0 s), than those not referred (28.3%/72.5 s) (p = 0.006/p < 0.001). Twelve of the 13 referred were offered a driving assessment by the DVLA. All 12 passed and returned to driving.

CONCLUSIONS

It is possible for individuals with post-stroke homonymous hemianopia to return to driving, where exceptional cases criteria are met. There is evidence to support use of the MAC as a clinical measurement of adaptation.IMPLICATIONS FOR REHABILITATIONIndividuals with post-stroke homonymous hemianopia should be fully informed regarding driving regulations that can differ between countries and sometimes different states within a country, as well as provided with the support and opportunity to consider a return to driving if appropriate.Professionals providing care within the stroke multi-disciplinary team should be aware that it is possible for patients with homonymous hemianopia to return to driving, when exceptional cases criteria are met.The mobility assessment course (MAC) should be considered as a clinical measurement of adaptation in homonymous hemianopia.A cut-off score of ≤25% omissions on MAC could be employed to determine those likely to adapt to hemianopia long-term and potentially return to driving.

Adaptation to post-stroke homonymous hemianopia - a prospective longitudinal cohort study to identify predictive factors of the adaptation process

PURPOSE

To determine any factors that predict how an individual will adapt to post-stroke hemianopic visual field loss, with close monitoring of the adaptation process from an early stage.

MATERIALS AND METHODS

The Hemianopia Adaptation Study (HAST) is a prospective observational longitudinal cohort clinical study. Adult stroke survivors (n = 144) with new onset homonymous hemianopia were monitored using standardised mobility assessment course (MAC) as the primary outcome measure of adaptation.

RESULTS

Several baseline variables were found to be good predictors of adaptation. Three variables were associated with adaptation status at 12-weeks post-stroke: inferior % visual field, % total MAC omissions, and MAC completion time (seconds). Baseline measurements of these variables can predict the adaptation at 12 weeks with moderate to high accuracy (area under ROC curve, 0.82, 95% CI 0.74-0.90). A cut-off score of ≤25% target omissions is suggested to predict which individuals are likely to adapt by 12-weeks post-stroke following gold standard care.

CONCLUSIONS

Adaptation to hemianopia is a personal journey with several factors being important for prediction of its presence, including MAC outcomes and extent of inferior visual field loss. A clinical recommendation is made for inclusion of the MAC as part of a functional assessment for hemianopia.Implications for rehabilitationThe mobility assessment course (MAC) should be considered as an assessment of mobility/scanning in the rehabilitation of patients with homonymous hemianopia.A cut-off score of ≤25% omissions on MAC could be employed to determine those likely to adapt to hemianopia long-term.Targeted support and therapy for patients with significant visual loss in the inferior visual field area should be considered.

The Impact of Diplopia on Reading

Aim:

To compare the effect of induced vertical diplopia (small and large separation) on reading speed and accuracy.

Methods:

The Radner Reading Chart (RRC) was used to measure reading speed (correct words per minute (wpm)) and accuracy (percentage). Accuracy was measured using two different methods: ‘accuracy-omission’ where only the omission of a word reduced the score, and ‘accuracy-addition and omission’ where any error reduced the score. Three viewing conditions were created using Fresnel prisms on plano glasses: a control condition without diplopia (6 prism dioptres (Δ) base up (BU) over each eye), small separation vertical diplopia (3Δ BU right eye and 3Δ base down (BD) left eye) and large separation vertical diplopia (6Δ BU right eye and 6Δ BD left eye). Viewing conditions were counterbalanced to minimise order effects.

Results:

Twenty-four participants were included with a mean age of 20.1 years. The mean reading speed in the control condition was 156.90 wpm. Both diplopic conditions significantly reduced the reading speed compared to the control condition, small separation diplopia to 62.75 wpm (p < 0.001) and large separation diplopia to 105.71 wpm (p < 0.001). The mean reading speed with small separation diplopia was significantly slower than the mean reading speed with large separation diplopia (p < 0.01). Median accuracy scores in the control and the large separation diplopia conditions were 100% using both methods of measuring accuracy. The small separation diplopia condition significantly reduced accuracy to 92.86% (accuracy-omission method) and to 57.50% (accuracy-addition and omission method) compared to the control condition (p < 0.01) and the large separation diplopia condition (p < 0.05).

Conclusion:

When vertical diplopia was induced using Fresnel prisms, diplopia of smaller separation resulted in the greatest reduction in reading speed and accuracy, compared to without diplopia and large separation diplopia.

Visual Search Performance in Patients with Vision Impairment: A Systematic Review

PURPOSE

Patients with visual impairment are constantly facing challenges to achieve an independent and productive life, which depends upon both a good visual discrimination and search capacities. Given that visual search is a critical skill for several daily tasks and could be used as an index of the overall visual function, we investigated the relationship between vision impairment and visual search performance.

METHODS

A comprehensive search was undertaken using electronic PubMed, EMBASE, LILACS, and Cochrane databases from January 1980 to December 2016, applying the following terms: "visual search", "visual search performance", "visual impairment", "visual exploration", "visual field", "hemianopia", "search time", "vision lost", "visual loss", and "low vision". Two hundred seventy six studies from 12,059 electronic database files were selected, and 40 of them were included in this review.

RESULTS

Studies included participants of all ages, both sexes, and the sample sizes ranged from 5 to 199 participants. Visual impairment was associated with worse visual search performance in several ophthalmologic conditions, which were either artificially induced, or related to specific eye and neurological diseases.

CONCLUSIONS

This systematic review details all the described circumstances interfering with visual search tasks, highlights the need for developing technical standards, and outlines patterns for diagnosis and therapy using visual search capabilities.

Effect of chromatic filters on visual performance in individuals with mild traumatic brain injury (mTBI): A pilot study

PURPOSE

Spectral filters have been used clinically in patients with mild traumatic brain injury (mTBI). However, they have not been formally assessed using objective techniques in this population. Thus, the aim of the present pilot study was to determine the effect of spectral filters on reading performance and visuo-cortical responsivity in adults with mTBI.

METHODS

12 adults with mTBI/concussion were tested. All reported photosensitivity and reading problems. They were compared to 12 visually-normal, asymptomatic adults. There were several test conditions: three luminance-matched control filters (gray neutral density, blue, and red), the patient-selected 'precision tint lens' that provided the most comfort and clarity of text using the Intuitive Colorimeter System, and baseline without any filters. The Visagraph was used to assess reading eye movements and reading speed objectively with each filter. In addition, both the amplitude and latency of the visual-evoked potential (VEP) were assessed with the same filters.

RESULTS

There were few significant group differences in either the reading-related parameters or VEP latency for any of the test filter conditions. Subjective improvements were noted in most with mTBI (11/12).

CONCLUSIONS

The majority of patients with mTBI chose a tinted filter that resulted in increased visual comfort. While significant findings based on the objective testing were found for some conditions, the subjective results suggest that precision tints should be considered as an adjunctive treatment in patients with mTBI and photosensitivity.

Atypical Sensory behaviours in children with Tourette's Syndrome and in children with Autism Spectrum Disorders

Certain visual disturbances make it difficult to read text and have been attributed to visual stress, also called "pattern-related visual stress". 12 Children with ASD, 12 children with Tourette's syndrome and without ASD and 12 controls, all matched on age and non verbal ability, participated in an experiment exploring sensory behaviours and visual stress. Reading rate and accuracy were assessed with the Wilkins Rate of Reading test with and without the Intuitive Overlays. Both the children with Tourette's and the children with ASD showed a higher prevalence of atypical sensory behaviours and symptoms of visual stress than the typically developing control children. Six out of twelve children with Tourette's syndrome (50%) read more accurately and over 15% more quickly with a coloured overlay. Four of the 12 children with ASD and none of the control children read over 15% more quickly with an overlay. The findings are discussed in relation to problems in sensory modulation.

The effect of spectral filters on VEP and alpha-wave responses

PURPOSE

Spectral filters are used to treat light sensitivity in individuals with traumatic brain injury (TBI); however, the effect of these filters on normal visual function has not been elucidated. Thus, the current study aimed to determine the effect of spectral filters on objectively-measured visual-evoked potential (VEP) and alpha-wave responses in the visually-normal population.

METHODS

The full-field (15°H×17°V), pattern-reversal VEP (20' check size, mean luminance 52cd/m(2)) was administered to 20 visually-normal individuals. They were tested with four Intuitive-Colorimeter-derived, broad-band, spectral filters (i.e., gray/neutral density, blue, yellow, and red), which produced similar luminance values for the test stimulus. The VEP N75 and P100 latencies, and VEP amplitude, were recorded. Power spectrum analysis was used to derive the respective powers at each frequency, and peak frequency, for the selected 9-11Hz components of the alpha band.

RESULTS

Both N75 and P100 latencies increased with the addition of each filter when compared to baseline. Additionally, each filter numerically reduced intra-session amplitude variability relative to baseline. There were no significant effects on either the mean VEP amplitude or alpha wave parameters.

CONCLUSIONS

The Intuitive Colorimeter filters significantly increased both N75 and P100 latencies, an effect which is primarily attributable (∼75%) to luminance, and in some cases, specific spectral effects (e.g., blue and red). VEP amplitude and alpha power were not significantly affected. These findings provide an important reference to which either amplitude or power changes in light-sensitive, younger clinical groups can be compared.

Visual performance and the use of colored filters in children who are deaf

PURPOSE

To assess visual performance and the effects of color overlays on reading in children who were deaf and children who could hear.

METHODS

Thirty-one children who were deaf (mean [± SD] age, 14 [± 1.99] years) and 39 children who could hear (mean [± SD] age, 13.58 [± 3.09] years) underwent an optometric examination with specific emphasis on near vision. Participants chose an overlay with color optimal for clarity and comfort and completed the Wilkins Rate of Reading Test both with and without an overlay of this color. Nineteen of the participants who were deaf were retested a year later with a modified rate of reading test that used only words that can readily be signed. This modified rate of reading test was repeated 1 week after its first administration.

RESULTS

Participants who were deaf had greater ametropia (p = 0.003), a more distant near point of convergence (p = 0.002), and reduced amplitude of accommodation (p < 0.001) compared with normal-hearing participants. All the children who were deaf chose a color overlay, with 45% choosing a yellow overlay, which increased the rate of reading by 18%. Only 66% of the participants who could hear chose an overlay, and it had no effect on reading speed. With the modified reading test, 7 of 19 (37%) again chose yellow. These participants showed a 9% increase in reading speed with the yellow overlay, which was repeatable 1 week later. The remainder showed no increase in rate of reading with their chosen overlay.

CONCLUSIONS

An eye examination of children who are deaf needs to include a comprehensive assessment of near visual function so that deficiencies of amplitude of accommodation, near point convergence, and ametropia can be treated. A yellow overlay improved reading speed in the participants who were deaf, whereas other colors did not, a finding at variance with earlier work on hearing populations.

The effect of spectral filters on visual search in stroke patients

Visual search impairment can occur following stroke. The utility of optimal spectral filters on visual search in stroke patients has not been considered to date. The present study measured the effect of optimal spectral filters on visual search response time and accuracy, using a task requiring serial processing. A stroke and control cohort undertook the task three times: (i) using an optimally selected spectral filter; (ii) the subjects were randomly assigned to two groups with group 1 using an optimal filter for two weeks, whereas group 2 used a grey filter for two weeks; (iii) the groups were crossed over with group 1 using a grey filter for a further two weeks and group 2 given an optimal filter, before undertaking the task for the final time. Initial use of an optimal spectral filter improved visual search response time but not error scores in the stroke cohort. Prolonged use of neither an optimal nor a grey filter improved response time or reduced error scores. In fact, response times increased with the filter, regardless of its type, for stroke and control subjects; this outcome may be due to contrast reduction or a reflection of task design, given that significant practice effects were noted.