Rodney Taylor, Doctor of Audiology, Advanced Studies in Tinnitus and Hyperacusis, Certified by the American Institute of Balance for Concussion and Vestibular Rehabilitation.
Visual Stress: Post-Concussion and Acquired Brain Injury (ABI)
Visual stress is a neurological condition characterized by the over-excitement of the visual area of the brain in response to light and patters. This often leads to a combination of physical discomfort, unpleasant visual symptoms, and perceptual processing difficulties that interfere with reading, attention, coordination, general health, and behavior.
Visual stress is neurological, it is not caused by refractive error and how the light is received byt eh retina, but by how the information is received and processed by the visual cortex. Because of this, it is not often identified in standard optometric exams.
Research, including brain scans using functional MRI, SPECT, NIRS, and QEEG technology have all demonstrated the hyperactivity of the visual cortex when presented with stimulating visual images. These studies have also demonstrated the immediate reduction in the hyperactivity when precision tinted lens filters are worn.
Visual stress can lead to misperception including intermittent blurring or doubling of an image. It is not solved with refraction corrective attempts. Patients will often complain of illusions of motion or images that appear to move or change when they are stable. Patient will sometimes have illusions of color (auras, sparkles or halo’s). There are often depth perception issues (the environment appears to be off-balance).
Visual stress can lead to discomfort in the form of headaches or migraines and typically, the symptoms are not helped with medication. Light sensitivity can be a debilitating symptom and to cope, often individuals will wear sunglasses indoors. Cognitive fatigue may occur with difficulties in focus and attention. Patients will sometimes complain of sore eyes and pain in the temple areas caused by strain through the perceptual distortions.
Wearing brimmed hats, sunglasses, or turning lights off
Tiring quickly when reading, taking frequent breaks
Skipping words or lines of texts, using a finger to track
Poor reading fluency and comprehension and easily distracted
Rubbing eyes and avoiding reading or looking at striped patterns
Following a concussion or acquired brain injury, patients may suffer from lingering light and pattern sensitivity, making it challenging to return to normal activities where reading printed and computer-based material is a fundamental requirement for professional and educational success and daily functioning. While some individuals may report no symptoms at all, others may report confusion, headache, decreased balance and visual disturbances which may include blurry vision, trouble focusing and sensitivity to light.
There have been several studies that report the photophobia and other visual symptoms following a concussion or brain injury may be alleviated by using precision tinted filters.
Visual stress is a condition characterized by a sensitivity to certain visual stimuli, leading to a range of physical and perceptual symptoms which may be alleviated with the use of individually prescribed coloured filter lenses. The intensity of these effects is greater when individuals are sensitive to light, pattern, and contrast, which can lead to cortical hyperactivation. Reading material, printed and on-screen, contains the attributes necessary to elicit visual stress symptoms and can lead to adverse symptoms including lowered tolerance of lights and screens, headaches, eye pain, dizziness, unbalanced sensations, nausea, and illusions of colour, shape and motion in text and in the environment.
In 1996, a study provided objective evidence for improvement of visual function provided by light-filtering lenses in patients who became photophobic after a TBI. Contrast sensitivity testing and assessment of reading rated added objective criteria for the clinical selection of light-filtering lenses in the treatment of TBI-induced photophobia (Jackowski et al, 1996).
Studies have proposed that the neurological disinhibition, resulting from a brain injury, may be responsible for the increased sensitivities and this disinhibition is similar to the hyperexcitability of visual stress (Chang et al, 2007).
Additionally, recent studies have reported that precision tinted lenses, or at least a wider range of filter colour options, provided increased visual comfort by reducing sensitivities to lights, improved reading performance, and allowing engagement in medically approved activities while minimizing the right of symptom exacerbation.
Kapoor (2012) (Chief of Vision Rehabilitation Services SUNY College of Optometry) outlined the visual-vestibular symptoms of ABI including physical and cognitive fatigue, eyestrain, headache, nausea, disequilibrium and an increased sensitivity to motion of visual stimuli (scrolling or quick moving screen images and movements of crowds). He also identified that these are all symptoms associated with visual stress and the hyperexcitement of the visual cortex, a state which has been demonstrated to be calmed and normalized with the application of precision tinted filters. The study concluded that treatment options include individually prescribed coloured filter lenses and that systems such as Colorimetry provide a systematic approach to determining an appropriate tint or coloured lens overlay.
A subsequent study by the SUNY College of Optometry in 2016, patient used the Intuitive Colorimeter device to select their optimal filter to provide the most comfort and clarity of text. The research team found that most patients with ABI chose a precision tinted filter that resulted in increased visual comfort and concluded that the use of precision tinted lenses would be a reasonable first step to increase comfort and should be considered as an adjunctive treatment in patients with ABI and photosensitivity (Kapoor, Fimreite et al, 2016).
In 2017, The University of Cincinnati Department of Neurology and Rehabilitation Medicine, a team addressed the use of dark sunglasses as a problematic solution to light sensitivity. Dark sunglasses, while they reduce the amount of incoming light, are not practical indoors or in low-light situations and add to eye strain as the information is dimmed and more difficult to process. Patients in this study were provided with a wide range of stock filter colours to choose from. The study found that sensitivity to certain wavelengths of light can be reduced with a strategy that includes colour-tinted glasses and that the use of these glasses may aid in the recovery process.
In 2018, the Journal of Neurotrauma published findings that the use of nonliquid crystal display (non-LCD) computer screens are effective in treating photosensitivity and computer screen intolerance (Clark et al, 2018).
Debacker et al., 2018, have estimated that more than 50% of the brain’s circuits involve vision and eye control. There are several systems that should be investigated in individuals with brain injuries that result in balance issues. These include the evaluation of the vestibulo-ocular reflex, the integration of visual and vestibular inputs, oculomotor testing, the evaluation of convergence and divergence and measures that require a verbal response from the patient. Researchers have investigated cortical activation patters in response to visual motion stimulation such as optokinetic stimulation and normal functioning individuals show distinct patters of cortical activations and deactivations that are reciprocal and simultaneious (Becker-Bense et al., 2012; Brandt et al., 1998; Deutschlander et al., 2008; Dieterich et al., 2003; Kikuchi et al., 2009; Kleinschmidt et al., 2002; and Rommer et al.,, 2015). Areas of cortical activation include the bilateral medial parieto-occipital visual areas, intraparietal culcus and the striate and extrastriate visual cortex. Cortical deactivations include the posterior insula, parieto-insular multisensory vestibular cortices, posterior region of superior temporal gyrus, inferior parietal lobule, anterior cingulate gyrus, hippocampus, and the corpus callosum.
Vestibular rehabilitation is a well-documented, exercise-based rehabilitation strategy designed to promote central compensation for vestibular dysfunction. These measures can be customized to accommodate the patients’ unique needs and goals and is implemented on and individual basis. The protocols include elements of both in-clinic and home-based exercise therapy. 20 to 50% of individuals that do not experience significant improvements with conventional vestibular rehabilitation may not improve due to a failure to adequately address symptoms of visual motion sensitivity (Rossi-Izquierdo et al., 2011, Pavlou et al., 2013). It is my protocol to address these issues initially with a neuro optometrist, who is part of my team. They are equipped with exercises to reduce susceptibility to disorientation and autonomic symptoms, use optokinetic stimulation, and serve to reduce visual over reliance, especially as it relates to perceptual and postural responses. Neuro optometrists deal with binocular vision (the ability to use two eyes together as a coordinated team to see a single three-dimensional image of surroundings), convergence (the eyes work together to create a single fused image of near objects by simultaneous adduction of both eyes) and convergence insufficiency. The prevalence in concussion is between 47 to 64% (Brahm et al., 2009; Capo-Aponte et al., 2012; Debacker et al., 2018). If diplopia develops or one eye turns outward 7 cm from the patient’s nose, this is a sign of convergence issues (Debacker et al., 2018). Saccades are abnormal in 30% of patients and smooth pursuit is abnormal in 60% of patients that suffer from head injury.
Chang, T., Ciuffreda, K., Kapoor, N., 2007. Critical flicker frequency and related symptoms in mild traumatic brain injury. Brain Inj., 21: 1055-1062.
Clarke, J. Hasselfiend, K., Bigsby, K., and Divine, 2017. Journal of Athletic Training. www.sciencedaily.com/releases/2017/07/170705132940.htm
Fimreite, V., Willeford, K., and Ciuffreda, K. (2016). Effect of chromatic filters on visual performance in individuals with mild traumatic brain injury (mTBI): A pilot study. Journal of Optometry, Dec: 9(4): 231-239.
Jackowski, M., Sturr, J., Taub, H., and Turk, M. (1996) Photophobia in patients with traumatic brain injury: Uses of light-filtering lenses to enhance contrast sensitivity and reading rate. NeuroRehabilitation. 6: 193-201.
Kapoor, N. (2012). Photosensitivity following traumatic brain injury. International Brain Injury Association.
Mansur, A., Hauer, T., Hussain,. M., et al. (2018). A nonliquid crystal display screen computer for treatment of photosensitivity and computer screen intolerance in post-concussion syndrome. Journal of Neurotrauma, Aug. 35:1886-1894.