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 o nly by inference based on anatomic and clinical findings. In this stud y, in five normal subjects we investigated the physiology of the lower eyelid retractors utilizing dynamic high resolution magnetic resonanc e imaging (MRI) with a custom designed surface coil. Measurements of t he excursion of the cornea, lower eyelid margin, and anterior edge of the inferior oblique muscle were made from scans taken in upgaze and d owngaze. 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 sim ilar in all cases. Thus, the length of the anterior capsulopalpebral f ascia between the tarsus and inferior oblique muscle remains constant in downgaze, and the source of the stretch in the lower eyelid retract ors lies in the posterior capsulopalpebral system, at the capsulopalpe bral head. High resolution eyelid MR has great potential to allow inve stigation of essential aspects of normal and pathologic eyelid anatomy and physiology.