Cervico-ocular Reflex Is Increased in People With Nonspecific Neck Pain

Background. Neck pain is a widespread complaint. People experiencing neck pain often present an altered timing in contraction of cervical muscles. This altered afferent information elicits the cervico-ocular reflex (COR), which stabilizes the eye in response to trunk-to-head movements. The vestibulo-ocular reflex (VOR) elicited by the vestibulum is thought to be unaffected by afferent information from the cervical spine. Objective. The aim of the study was to measure the COR and VOR in people with nonspecific neck pain. Design. This study utilized a cross-sectional design in accordance with the STROBE statement. Methods. An infrared eye-tracking device was used to record the COR and the VOR while the participant was sitting on a rotating chair in darkness. Eye velocity was calculated by taking the derivative of the horizontal eye position. Parametric statistics were performed. Results. The mean COR gain in the control group (n = 30) was 0.26 (SD = 0.15) compared with 0.38 (SD = 0.16) in the nonspecific neck pain group (n = 37). Analyses of covariance were performed to analyze differences in COR and VOR gains, with age and sex as covariates. Analyses of covariance showed a significantly increased COR in participants with neck pain. The VOR between the control group, with a mean VOR of 0.67 (SD = 0.17), and the nonspecific neck pain group, with a mean VOR of 0.66 (SD = 0.22), was not significantly different. Limitations. Measuring eye movements while the participant is sitting on a rotating chair in complete darkness is technically complicated. Conclusions. This study suggests that people with nonspecific neck pain have an increased COR. The COR is an objective, nonvoluntary eye reflex and an unaltered VOR. This study shows that an increased COR is not restricted to patients with traumatic neck pain.