Normative surface electromyography values for the orbicularis oculi muscle in healthy control subjects

The orbicularis oculi muscle (OOM) is essential for eyelid function, protecting the ocular surface and maintaining visual health. Although surface electromyography (sEMG) offers a non-invasive means to assess OOM activity, its clinical utility has been limited by the absence of normative reference values. This study aimed to establish normative sEMG values for the OOM to enhance diagnostic accuracy and support therapeutic applications. sEMG recordings were collected from healthy participants during both gentle eyelid closure (GEC) and maximal voluntary contraction (MVC) using a single electrode positioned in the mid-pretarsal area. Muscle activation was quantified via root mean square (RMS) values, and data were standardized using normalization techniques including %MVC. Participants had a mean age of 63.12 years (range 27–87 years). The upper confidence intervals were as follows: %MVC at 29.88% (97.5% CI 29.11–30.64%), RMS MVC at 303µV (97.5% CI 281–325 µV), and RMS GEC at 13.57 µV (97.5% CI 12.42–14.72 µV). RMS values during gentle eyelid closure exhibited high consistency and narrow confidence intervals, suggesting its potential as a reliable clinical marker for assessing neurophysiological function, particularly in lagophthalmos. No previously reported values for the orbicularis oculi muscle are available for comparison.