• Kunal R Sinha, Sara Al Shaker, Amir Yeganeh, Tyler Moreno, and Daniel B Rootman.
• David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, U.S.A.
• Ophthal Plast Reconstr Surg. 2019 Jan 1; 35 (1): 85-90.

PurposeThe purpose of this study is to explore mechanical and co-innervational factors involved in both voluntary and involuntary brow elevation among people affected by ptosis and dermatochalasis.MethodsIn this prospective cohort study of normal controls and eyelids with ptosis or dermatochalasis, marginal reflex distance (MRD1) and brow height were measured under the following conditions: neutral position, involuntary mechanical brow elevation, voluntary brow elevation, and maximal eyelid opening. The primary outcome measure was change in MRD1. Secondary outcome measures included brow height and coupling (mm brow height change per mm MRD1 change). Analysis of variance and t tests were performed for intra- and intercondition comparisons, respectively.ResultsMechanical (involuntary) brow elevation significantly raised MRD1 in control eyelids and eyelids with dermatochalasis, but not in eyelids with ptosis. Voluntary brow elevation produced significantly greater brow height than maximal eyelid opening in controls and eyelids with dermatochalasis, but not in eyelids with ptosis. Maximal eyelid opening increased MRD1 greater than voluntary brow elevation significantly in control eyelids, but not in eyelids with dermatochalasis or ptosis. Coupling of the brow and eyelid margin during maximal eyelid opening was significantly greater in eyelids with ptosis relative to controls.ConclusionsIn eyelids with ptosis, mechanical brow elevation does not change eyelid position; however, voluntary brow elevation raises eyelid position to a similar position as maximal eyelid opening. These results argue against the contention that the brow is elevated to mechanically lift the eyelid in ptosis and instead suggest that the brow elevation is driven by efforts to raise the eyelid, possibly via co-innervation.

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