Objectifying eye movements during rapid number naming: Methodology for assessment of normative data for the King–Devick test

Abstract

ObjectiveConcussion is a major public health problem and considerable efforts are focused on sideline-based diagnostic testing to guide return-to-play decision-making and clinical care. The King–Devick (K–D) test, a sensitive sideline performance measure for concussion detection, reveals slowed reading times in acutely concussed subjects, as compared to healthy controls; however, the normal behavior of eye movements during the task and deficits underlying the slowing have not been defined. MethodsTwelve healthy control subjects underwent quantitative eye tracking during digitized K–D testing. ResultsThe total K–D reading time was 51.24 (±9.7) seconds. A total of 145 saccades (±15) per subject were generated, with average peak velocity 299.5°/s and average amplitude 8.2°. The average inter-saccadic interval was 248.4ms. Task-specific horizontal and oblique saccades per subject numbered, respectively, 102 (±10) and 17 (±4). Subjects with the fewest saccades tended to blink more, resulting in a larger amount of missing data; whereas, subjects with the most saccades tended to make extra saccades during line transitions. ConclusionsEstablishment of normal and objective ocular motor behavior during the K–D test is a critical first step towards defining the range of deficits underlying abnormal testing in concussion. Further, it sets the groundwork for exploration of K–D correlations with cognitive dysfunction and saccadic paradigms that may reflect specific neuroanatomic deficits in the concussed brain.