Purpose: To assess the trigeminal blink reflex in chronic orbital pain and its modification by orbital anesthetic injections using a novel blink reflexometer.
Methods: The EyeStat (Generation 3, Blinktbi, Inc. Charleston, SC) is a device that triggers and analyzes the carbon dioxide puff-evoked trigeminal blink response. In this prospective study, CO2 puffs were delivered to each eye of 6 patients with unilateral, chronic orbital pain at baseline and 30 minutes after unilateral orbital anesthetic injections consisting of lidocaine and bupivacaine. Ten healthy subjects underwent the testing once without injections. Main outcome measures were comparison of the average of the right and left eyelid responses to stimuli given to the right or left eye (to assess afferent response in the right vs left eye) and comparison of the right eyelid to left eyelid responses to both the right and left stimuli (to assess efferent response in the right vs left eye).
Results: In 10 healthy patients, direct blink response of the stimulated eyelid exceeded the consensual response of the opposite eyelid (latency p = .001, excursion p = .04, time to close p = .03). Among the 6 pain patients, eyelid kinematics for afferent trigeminal input were similar between the affected eye and the fellow eye. However, after injection, the afferent latency of the affected eye was significantly prolonged relative to the unaffected eye (p = .006). Efferent blink responses were similar between the two eyelids at all time points.
Conclusion: Peribulbar anesthetic injections modulate mechanical afferent input to the trigeminal blink reflex.
Keywords: Chronic orbital pain; blink latency; high-speed video analysis; nerve blocks; trigeminal blink reflex.