Eyelid heat pain sensitivity in healthy participants

Introduction: Chronic ocular pain (COP) is a widespread pain condition that presents clinical challenges, has heterologous and overlapping etiologies across patients, and can have a debilitating effect on quality of life. It can manifest with neuropathic-like symptoms as well as dysesthesias associated with afferent disruption, brain dysfunction, or both, complicating diagnosis and treatment. Quantitative sensory testing (QST) has been used extensively in individuals with chronic pain to detect abnormal peripheral and central nervous system function. Investigating relevant sensory thresholds is crucial for integrating QST into ocular pain assessments. Objectives: This study aimed to determine heat pain thresholds on the eyelid in healthy participants. Furthermore, we sought to evaluate the eyelid as a feasible and suitable body site for COP investigation using QST. Methods: Heat pain thresholds were measured in 80 healthy participants at 2 study sites using the method of limits at 3 stimulation sites: the upper eyelid, the forehead, and the volar forearm. Results: Analysis revealed a significantly lower estimated marginal mean (EMM) heat pain threshold on the eyelid (42.5 ± 0.4 EMM ± SE) compared with the forehead (46.6 ± 0.4 EMM ± SE) ( P < 0.001) and forearm (46.4 ± 0.4 EMM ± SE) ( P < 0.001). These differences were statistically significant regardless of sex, study site, or age. No differences were found between the forehead and the forearm ( P = 1.00). Conclusion: The eyelid is a clinically relevant site for QST in the investigation of ocular and trigeminal function, and this study sets the groundwork for applying eyelid QST in future research of ocular pain and disease etiology.