Influence of neck torsion on near point convergence in subjects with idiopathic neck pain.

BACKGROUND: People with neck pain (NP) experience sensorimotor and oculomotor deficits thought to be due to abnormal cervical afferent input. Convergence insufficiency (CI) measured by near point convergence (NPC) may be a feature in NP and neck torsion might help to differentiate a cervical cause.

OBJECTIVES: This study aimed to investigate repeatability and reliability of NPC in neutral and torsion and compare between idiopathic NP and controls along with correlation to the Convergence Insufficiency Symptom Survey (CISS).

DESIGN: Comparative cross sectional observational study.

METHOD: A Royal Airforce (RAF) Rule measured NPC with the neck in neutral and in 45° torsion to the left and right in 42 subjects. A revised 15 item CISS was also completed. The average of 3 trials in each position and torsion difference were calculated. Within one week, NPC inter-rater and test-retest reliability was evaluated in 10 subjects.

RESULTS: A significant NPC torsion difference was demonstrated in participants with NP compared to controls (P = 0.01). No significant differences were seen for NPC values in neutral (P = 0.73). High inter-rater reliability (ICC = 0.95) and repeatability (ICC = 0.84) was obtained. No correlations were present between the CISS and NPC measures (r ≤ 0.18).

CONCLUSIONS: NPC is impaired in neck torsion compared to neutral in NP supporting a cervical afferent cause. NPC, measured using the RAF Rule, is a reliable and repeatable measure and can be used to assess NPC and CI in those with NP. Objective rather than self-reported measures should be used to examine CI in NP.