Faculty Bibliography

Accurate detection and interpretation of eye movement abnormalities often guides differential diagnosis, discussions on prognosis and disease mechanisms, and directed treatment of disabling visual symptoms and signs. A comprehensive clinical eye movement examination is high yield from a diagnostic standpoint; however, skillful recording and quantification of eye movements can increase detection of subclinical deficits, confirm clinical suspicions, guide therapeutics, and generate expansive research opportunities. This review encompasses an overview of the clinical eye movement examination, provides examples of practical diagnostic contributions from quantitative recordings of eye movements, and comments on recording equipment and related challenges.

OBJECTIVE:The Mobile Universal Lexicon Evaluation System (MULES) is a test of rapid picture naming under investigation. Measures of rapid automatic naming (RAN) have been used for over 50 years to capture aspects of vision and cognition. MULES was designed as a series of 54 grouped color photographs (fruits, random objects, animals) that integrates saccades, color perception and contextual object identification. We examined MULES performance in youth, collegiate and professional athletes at pre-season baseline and at the sidelines following concussion. METHODS:Our study teams administered the MULES to youth, collegiate and professional athletes during pre-season baseline testing. Sideline post-concussion time scores were compared to pre-season baseline scores among athletes with concussion to determine degrees and directions of change. RESULTS:Among 681 athletes (age 17 ± 4 years, range 6-37, 38% female), average test times at baseline were 41.2 ± 11.2 s. The group included 280 youth, 357 collegiate and 44 professional athletes; the most common sports were ice hockey (23%), soccer (17%) and football (11%). Age was a predictor of MULES test times, with longer times noted for younger participants (P < .001, linear regression). Consistent with other timed performance measures, significant learning effects were noted for the MULES during baseline testing with trial 1 test times (mean 49.2 ± 13.1 s) exceeding those for trial 2 (mean 41.3 ± 11.2 s, P < .0001, paired t-test). Among 17 athletes with concussion during the sports seasons captured to date (age 18 ± 3 years), all showed increases (worsening) of MULES time scores from pre-season baseline (median increase 11.2 s, range 0.6-164.2, P = .0003, Wilcoxon signed-rank test). The Symptom Severity Score from the SCAT5 Symptom Evaluation likewise worsened from pre-season baseline following injury among participants with concussion (P = .002). CONCLUSIONS:Concussed athletes demonstrate worsening performance on the MULES test compared to their baseline time scores. This test samples a wide network of brain pathways and complements other vision-based measures for sideline concussion assessment. The MULES test demonstrates capacity to identify athletes with sports-related concussion.

The objective analysis of eye movements has a significant history and has been long proven to be an important research tool in the setting of brain injury. Quantitative recordings have a strong capacity to screen diagnostically. Concurrent examinations of the eye and upper limb movements directed toward shared functional goals (e.g., eye-hand coordination) serve as an additional robust biomarker-laden path to capture and interrogate neural injury, including acquired brain injury (ABI). While quantitative dual-effector recordings in 3-D afford ample opportunities within ocular-manual motor investigations in the setting of ABI, the feasibility of such dual recordings for both eye and hand is challenging in pathological settings, particularly when approached with research-grade rigor. Here we describe the integration of an eye tracking system with a motion tracking system intended primarily for limb control research to study a natural behavior. The protocol enables the investigation of unrestricted, three-dimensional (3D) eye-hand coordination tasks. More specifically, we review a method to assess eye-hand coordination in visually guided saccade-to-reach tasks in subjects with chronic middle cerebral artery (MCA) stroke and compare them to healthy controls. Special attention is paid to the specific eye- and limb-tracking system properties in order to obtain high fidelity data from participants post-injury. Sampling rate, accuracy, permissible head movement range given anticipated tolerance and the feasibility of use were several of the critical properties considered when selecting an eye tracker and an approach. The limb tracker was selected based on a similar rubric but included the need for 3-D recording, dynamic interaction and a miniaturized physical footprint. The quantitative data provided by this method and the overall approach when executed correctly has tremendous potential to further refine our mechanistic understanding of eye-hand control and help inform feasible diagnostic and pragmatic interventions within the neurological and rehabilitative practice.

BACKGROUND:Concussion leads to neurophysiologic changes that may result in visual symptoms and changes in ocular motor function. Vision-based testing is used increasingly to improve detection and assess head injury. This review will focus on the historical aspects and emerging data for vision tests, emphasizing rapid automatized naming (RAN) tasks and objective recording techniques, including video-oculography (VOG), as applied to the evaluation of mild traumatic brain injury. METHODS:Searches on PubMed were performed using combinations of the following key words: "concussion," "mild traumatic brain injury," "rapid automatized naming," "King-Devick," "mobile universal lexicon evaluation system," "video-oculography," and "eye-tracking." Additional information was referenced from web sites of vendors of commercial eye-tracking systems and services. RESULTS:Tests of rapid number, picture, or symbol naming, termed RAN tasks, have been used in neuropsychological studies since the early 20th century. The visual system contains widely distributed networks that are readily assessed by a variety of functionally distinct RAN tasks. The King-Devick test, a rapid number naming assessment, and several picture-naming tests, such as the Mobile Universal Lexicon Evaluation System (MULES) and the modified Snodgrass and Vanderwart image set, show capacity to identify athletes with concussion. VOG has gained widespread use in eye- and gaze-tracking studies of head trauma from which objective data have shown increased saccadic latencies, saccadic dysmetria, errors in predictive target tracking, and changes in vergence in concussed subjects. Performance impairments on RAN tasks and on tasks recorded with VOG are likely related to ocular motor dysfunction and to changes in cognition, specifically to attention, memory, and executive functioning. As research studies on ocular motor function after concussion have expanded, so too have commercialized eye-tracking systems and assessments. However, these commercial services are still investigational and all vision-based markers of concussion require further validation. CONCLUSIONS:RAN tasks and VOG assessments provide objective measures of ocular motor function. Changes in ocular motor performance after concussion reflect generalized neurophysiologic changes affecting a variety of cognitive processes. Although these tests are increasingly used in head injury assessments, further study is needed to validate them as adjunctive diagnostic aids and assessments of recovery.