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.
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.