Nonstrabismic binocular dysfunctions and cervical complaints: The possibility of a cross-dysfunction

The aim of this study is to establish a relationship between non-strabismic binocular dysfunction and neck pain. One hundred twelve participants underwent binocular vision assessment by evaluating horizontal heterophoria, horizontal and vertical fusional vergence ranges and vergence facility. The subjects were classified into two groups: binocular anomalies and normal binocular function. Neck complaints were measured with the Neck Disability Index, visual analogue scale, cervical range of motion, deep-flexor muscle activation score (AS) and performance index (PI). Our results showed that participants with low AS had significantly altered values of lateral phoria (near) (mean = -6.99 SD ± 6.96 PD) and PFV (near) blur (mean = 9.49 SD ± 5.45 PD) against those who presented normal AS (lateral phoria (near) mean = -3.64 SD ± 6.37 PD; PFV (near) blur mean = 12.84 SD ± 6.20 PD). In addition, participants with NFV (near) recovery outside the norm had a significantly lower right side-bending (mean = 35.63 SD ± 8.35 PD) than those within the standard (mean = 39.64 SD ± 9 PD). The subjects with binocular vision impairment showed a diminished response to the deep cervical musculature, with low AS and PI, as well as a tendency to suffer from cervicalgia of more than three months' evolution and a lower range of motion.