Riquelme I, Henne C, Flament B, Legrain V, Bleyenhauft Y, Hatem SM.
Research in Developmental Disabilities 2015;43-44:61-71.
doi: 10.1016/j.ridd.2015.06.009
 
By: Kristen Vincent (Class of 2017)
Pennsylvania College of Optometry, Salus University

​Prism adaptation (PA) is an efficient therapeutic mediation to shift the visual field horizontally. The horizontal movement of the visual field reveals a clear directional influence on visuo-motor and sensory-motor communications. To offset the visual field deviation, the individual has to reestablish his mobility, leading to a modification of sensorimotor coordinates. Removal of the prism glasses creates the egocentric coordinates of the sensory-motor reference frame to be altered, thus generating immediate visual and proprioceptive adjustments in the direction of pointing and reaching, named after-effects. After-effects are the critical component in determining the value of PA.
 
PA has been a successful intervention for performance adaptation in a variety of spatial task in adults: both in healthy individuals and in patients with unilateral neglect following stroke. Due to its abiding influence, PA is considered an efficient method for rehabilitating unilateral spatial neglect by shifting the neglected hemisphere into the “seeing” field.
 
PA is also utilized for correcting strabismus in children, and research shows that even infants at 6-9 months of age exhibit adaptive responses to PA. The visuo-motor relationship is an attractive focus for therapeutic mediation in children since perceptuo-motor procedural learning fundamentally occurs at school age. While unilateral neglect, described as a deficit in attention and appreciation of stimuli on the paretic side of the body, has been characterized in children with cerebral damage, the achievability of PA in these children had not been explored prior to this study.
 
While wearing prismatic glasses, PA involves the simultaneous performance of a sensorimotor task within the visual space. Repetition of pointing movements toward visual targets is regarded as the standard procedure, both in healthy individuals and in unilateral neglect patients. As an alternative procedure to the repetitive and tedious pointing tasks, a series of visuomotor activities performed with daily life objects i.e. ecological tasks, has been recommended as more varied and appealing for long-term management. Therefore, the present study investigated the beneficial effects of PA supplemented with selected game tasks as a feasible, child-friendly alternative to the aforementioned ecological task procedures proposed for adults. It also aimed at determining whether one session of prism adaptation could generate substantial visuomotor after-effects in children with unilateral brain lesion compared with neutral glasses.
 
The participants of the study included 21 children with unilateral brain lesion resulting in hemiparesis. The children were divided into two study arms: one group was randomized to prism treatment, the other to neutral glasses. The intervention for all participants involved one daily task session on two consecutive days, one day consisting of ecological tasks and the other of game tasks. Children were encouraged by verbal instruction to perform all tasks bimanually for a duration of 20 minutes. All procedures were conducted while children wore glasses: prismatic glasses in the prism group and neutral glasses in the control group. Prismatic glasses deviated the visual field 20 prism diopters (approximately 11 degrees) towards the non-paretic side.
 
During the ecological task session, children completed an assortment of 10 visuomotor activities based on the handling of common daily life objects. During the game task session, participants completed an assortment of 10 common children games selected for promoting lateral investigation of space. To measure visuomotor adaptations provoked by the intervention, children executed two open-loop pointing tests just before and immediately after each intervention: (1) the visual open-loop pointing test, i.e. a visuoproprioceptive test with opened eyes, and (2) the subjective straight ahead pointing test, i.e. a proprioceptive test with closed eyes. Instantaneous effects of PA have been correlated with changes of these pointing assessments.
 
After intervention with ecological tasks in the prism group, visuoproprioceptive pointing errors of 9 (out of 11) children had drifted towards the hemiparetic side. In this same group, after intervention with game tasks, visuoproprioceptive pointing errors of 9 (out of 11) children had drifted towards the hemiparetic side. In contrast, the control group presented these findings: visuoproprioceptive pointing errors of only 1 (out of 10) child displayed a shift toward the hemiparetic side after intervention with ecological tasks, and visuoproprioceptive pointing errors of 4 (out of 10) children displayed a shift towards the hemiparetic side after intervention with game tasks.
 
Results were similar for the proprioceptive test. After intervention with ecological tasks for the prism group, proprioceptive pointing errors of 10 (out of 11) children had drifted towards the hemiparetic side and after intervention with game tasks, proprioceptive pointing errors of 9 (out of 11) children had drifted towards the hemiparetic side. In contrast, in the control group, proprioceptive pointing errors of 7 (out of 10) children displayed a shift towards the hemiparetic side after intervention with ecological tasks, and proprioceptive pointing errors of 4 (out of 10) children displayed a shift towards the hemiparetic side after intervention with game tasks.
 
This was the first study to justify the feasibility and effectiveness of prism adaptation in a pediatric population with unilateral brain lesion. It was proven that one single session of PA therapy was successful in stimulating after-effects, measured by subjective straight ahead pointing and visual open-loop pointing. As anticipated, PA in hemiparetic children provoked visuoproprioceptive after-effects towards the paretic hemispace, i.e. in a direction contralateral to the optical shift created by PA. On an interesting note, these after-effects were more distinct in children with right hemispheric lesion. A greater proprioceptive pointing error towards the paretic hemispace in the prism group compared to the control group was also observed. Moreover, game tasks presented to be as effective as ecological tasks at provoking prism adaptation-related after-effects. The children were more engaged and interested while playing common games than while conducting ecological tasks, and therefore games may promise longer interventions in children with visuospatial impairments.
 
After-effects are the clinical correlate of modified cortical networks involved in spatial attention and awareness while performing neglect recovery. Consequently, the manifestation of after-effects in children with unilateral brain lesion proposes the presence of short-term plasticity of cortical areas within the visual reference frame.
 
The prismatic glasses (20 prism diopters) utilized in this study induced a shift of the visual field by about 11 degrees during the performance of tasks and resulted in after-effects of 4 degrees on average. A larger magnitude of prisms would have afforded a larger after-effect, but this could have produced other disadvantages including distortion and unmeasurable displacement while pointing.
 
Limitations of the study included small sample size and it comprised primarily of children with right hemiparesis (i.e. left hemispheric lesion). The results proposed that PA effects could be larger in children with left hemiparesis (i.e. right hemispheric lesion), yet a larger and more homogenous sample is indicated to corroborate the reliability of this finding.
 
Since PA therapy requires repetitive intervention to produce long-lasting effects, further research is necessary to establish the efficiency of a long-term intervention in the rehabilitation of brain-damaged children with visuospatial deficits and/or neglect. Future studies should also assess different intervention durations to authenticate the most effective therapeutic dosage scheme in children. Lastly, exploration of acquiring differential improvement of extensive cognitive, motor, and sensory effects in children, as has been presented in adults, is needed. This study lays the groundwork for future research on the subject and unravels new possibilities for the rehabilitation of children with neurological dysfunctions.

Fimreite V, Willeford KT, Ciuffreda KJ. Journal of Optometry 2016;9(4):231-239.

By Sato Mananian
AZCOPT OD 2019 Candidate
 
The purpose of this pilot study was to investigate how spectral filters influence reading performance in patients with mild traumatic brain injury (mTBI). Patients who have suffered an mTBI often suffer a deficit in reading skills such as pursuits, saccades and fixations. These deficits are primarily due to an oculomotor dysfunction. Accommodative dysfunction and light sensitivity may also contribute to a patient’s decreased reading ability. Light sensitivity is a common sequela of mTBI and can often be treated with band pass spectral lenses to reduce the intensity of light patients see. It has also been found that filters that particularly transmit blue light decrease accommodative demand, providing additional relief to these patients. This study sought to determine the optimal tint for improved reading ability in mTBI patients with the above-mentioned symptoms.

The study examined 12 individuals recruited from SUNY State College of Optometry who had suffered concussions from either a sport related accident, a car accident or another traumatic event. These participants were past the natural recovery phase of 6-9 months. The subjects had a BCVA of 20/20 at distance and near, OD, OS and OU. Eligibility criteria for the study included a diagnosis of mTBI based off a loss of consciousness for less than 30 minutes, post traumatic amnesia lasting less than 24 hours, and a Glasgow Coma Scale score of 13-5. The average age of subjects in the study was 35 years old, with a range of 21-60 years of age. The study used a control group made up of 12 visually normal individuals with an average age of 23.3 years of age and a mean spherical refractive error of -2.75D, ranging from +1.25D to -6.25D. The control group excluded individuals with a history of seizures, strabismus, amblyopia or ocular systemic disease.

Data was gathered using the Visual Evoked Potential (VEP) and the Visagraph II. On the VEP, subjects viewed a visual stimulus of an alternating black and white checkerboard pattern. The visual stimuli were viewed binocularly through one of the following three spectral filters: (a) gray/neutral, (b) blue (425 nm) and (c) red (650 nm). The gray/neutral density filter was used as the control. Studies done using the Visagraph employed the same three band-pass chromatic filters as the VEP as well as viewing glasses. These filters are commonly used in this patient population to reduce symptoms of photophobia.

The results of the study showed that filter type did not alter the number of fixations, regressions, fixation duration, or VEP amplitude and latency. Patients with mTBI made more fixations and regressions than controls during testing. When comparing findings, no effects were seen in five of the six test parameters due to filter type used. There were notable differences in reading rate for these two groups with the different filters. However, although there was no statistically significant correlation with filter and performance on reading rate tests or VEP amplitude, it was noted that 6 subjects in the control group were shown to read best with the blue filter. Similarly, in subjects who suffered an mTBI preferred the precision tint filters when reading.

The study concluded that reduction in overall luminance due to the use of filters may have been the primary cause of increased visual comfort because of the predisposition to photophobia in this population regardless of the color or type of filter used. Furthermore, the preferences for certain filters in each group may indicate an increase in visual comfort for these patients, which regardless of its statistical significance, is valuable information that can be used to help this unique patient base.
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The researchers hope to repeat the study with a larger sample size, longer test period, and reassessment of patient skills in real life settings. The future study will further observe the use of tinted filters with the hopes of discovering additional benefits for mTBI patients. Ideally, the study would like to set the standard for future doctors to use spectral lenses in early treatment for symptomatic relief in this patient base before long term therapy is able to offer relief. 

Congratulations are in order as this year's wiring competition have been selected!

Student Winner
Early Detection of Visual Dysfunction in 5th and 6th Grade Readers Based on Head Movements and Head Position During Reading Activities
Nikita Katoozi 
Pacific University College of Optometry 
Class of 2018

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Infantile Nystagmus: Classification, Assessment and Management, A Review
Nathalia Broderick, OD
Pediatric and Infant Vision Optometry Resident at SUNY College of Optometry