Physiology of the lower eyelid retractors: tight linkage of the anterior capsulopalpebral fascia demonstrated using dynamic ultrafine surface coil MRI.

Although the histologic anatomy of the lower eyelid retractors is well defined, the physiology of the lower retractors has been determined only by interference based on anatomic and clinical findings. In this study, in five normal subjects we investigated the physiology of the lower eyelid retractors utilizing dynamic high resolution magnetic resonance imaging (MRI) with a custom designed surface coil. Measurements of the excursion of the cornea, lower eyelid margin, and anterior edge of the inferior oblique muscle were made from scans taken in upgaze and downgaze. We found that the corneal movement was substantially greater than the movement of the eyelid margin, a finding that can readily be made clinically. A more important result was that the movement of the eyelid margin and the movement of the inferior oblique margin were similar in all cases. Thus, the length of the anterior capsulopalpebral fascia between the tarsus and inferior oblique muscle remains constant in downgaze, and the source of the stretch in the lower eyelid retractors lies in the posterior capsulopalpebral system, at the capsulopalpebral head. High resolution eyelid MR has great potential to allow investigation of essential aspects of normal and pathologic eyelid anatomy and physiology.