A Novel Technique for Measuring Eyelid Force.

Abstract

We present a novel technique to directly measure the eyelid upward force generation. This technique can be used during routine clinical examination using an inexpensive, portable force gauge. This prospective case series was conducted January to June 2015 in an ophthalmology clinic affiliated with a tertiary care medical center. A convenience sample of 42 patients (40-90 years of age) without known eyelid pathology participated. The eyelid upward net force generated was measured directly using a handheld dynamometer noninvasively attached to the upper eyelid. Comparison of the eyelid-brow upward force generated with eyelid upward net force generated allowed us to assess the contribution of levator and frontalis muscles to the force generated during upgaze. Data were evaluated with relation to gender and age. Upper eyelid force generated was 53.3 g OD and 53.9 g OS; the generated force during frontalis muscle fixation was 38.4 g OD and 41.1 g OS. The levator and frontalis muscles showed a 3:1 ratio respectively in their contribution to the force generated during upgaze. Although no statistically significant differences were seen between eyes, gender, or within age groups, younger patients showed increased generating force which is attributed to the levator muscle. Interclass correlation coefficient showed virtually no correlation between clinical eyelid assessments and direct muscle force measurement. Reliability for repeated direct force measurements by the same physician was strong, with interclass correlation coefficient 0.951 to 0.969. No adverse events occurred. We describe a simple, reliable, inexpensive, new method for assessing upper eyelid upward force generation. Because the levator muscle serves as the primary contributor to eyelid elevation, this directly measurable eyelid assessment may help to increase understanding of its functional contribution and assessment when assessing eyelid pathologies.