Background: Edge light pupil cycle time (ELPCT) is one of the eye's light reflexes. Studies have shown ELPCT to be a measurable constant, unaffected by visual acuity, refractive error, eye color, pupil size, or sex. Control of this reflex occurs through the autonomic nervous system. Various authors suggest that spinal manipulative techniques can produce distant effects mediated in part by alterations in autonomic tone after intervention.
Objective: To investigate the effects of a C1-2 high-velocity, low-amplitude manipulation on ELPCT.
Design: A single-group, randomized pilot study without a control group.
Methods: Thirteen men (mean age 24.2 years) without a history of eye disease or central or autonomic nervous system pathologic conditions had their ELPCT measured before and after manipulation. The manipulation comprised a high-velocity, low-amplitude rotatory thrust, localized to the C1-2 joint on the left (n = 6) or right (n = 7) eye, determined randomly.
Results: ELPCT measures demonstrated a significant difference for both eyes before and after manipulation (P = .002; the right eye, P = .027; the left eye, P = .046).
Conclusion: This suggests that ELPCT, which is mediated through the autonomic nervous system, can be directly influenced by high-velocity manipulation to the upper cervical spine.