Introduction: The King-Devick (KD) test of rapid number-naming, a sensitive and rapid performance measure, adds a visual dimension to sideline testing for concussion. We performed a laboratory-based eye movement study during performance of the KD test. We sought to determine if having English as a second language results in slower KD reading times or changes in eye movements.
Methods: We tested 27 native English speakers (NES) (mean age 32) and 27 subjects for whom English was a second language (ESL) (mean age 34). Participants had no history of concussion. Participants performed a computerized version of the KD. Simultaneous infrared-based videooculographic (VOG) recordings were performed using the Eyelink1000+. A Bilingual Dominance Scale survey, which quantifies primary versus secondary language dominance, was completed by all ESL subjects.
Results: Digitized KD reading times were significantly prolonged for ESL participants, compared to NES (54.4 ± 15.4 sec vs. 42.8 ± 8.6 sec, p=0.001, t-test). Average inter-saccadic intervals (ISI), a combined measure of saccade latency and fixation duration), were significantly longer for ESL participants (402 ± 116.9 msec vs. 317.7 ± 53.9 msec, p=0.002, t-test). The total number of saccades for ESL participants was significantly higher (149 ± 28 vs. 135 ± 18, p=0.03, t-test).
Conclusions: This study highlights performance disparities that linguistics may impose on rapid number-naming tasks. Concussion screening is best implemented by establishment of pre-season baselines to allow for intra-subject comparisons after impact in sport. If preseason baseline data are unavailable, caution should be taken in comparing non-native English speaker reading times to a NES normative control KD time database.
- Laboratory-based eye movement study completed to determine the effect of English as a second language on the K-D Test and eye movement performance.
- Digitized K-D reading times were prolonged for ESL participants.
- Average inter-saccadic intervals (ISI) represents a combined measure of saccade latency and fixation duration.
- ISI was longer for ESL participants and total number of saccades for ESP participants was higher.
- Disparities that linguistics may impose on rapid number naming highlights the importance of proper concussion screening implementation with establishing individual pre-season baselines.
- Caution should be taken in comparing ESL performance to a normative control database.