This chapter deals with the author’s concepts regarding the height and depth of an eyelid crease, which change in different view positions with respect to the patient’s gaze, as well as the clinician’s observing angle.
An individual’s upper eyelid crease height varies in its measurement and is influenced by various factors, including resting position, angle of observation and presence of associated ocular abnormality. Its effects should be taken into consideration in planning primary aesthetic and revisional surgery of the eyelids.
Anatomic Definition of an Upper Eyelid Crease
The upper eyelid crease is a natural indentation of the eyelid skin, usually found along the level of the superior tarsal border, which is apparent when the subject opens their eyelid ( Figure 19-1 ). It is believed to be a result of contraction of the distal fibers of the levator aponeurosis, pulling up on the tarsus as well as the pretarsal skin and orbicularis in a superior–posterior direction against a relaxed preseptal segment of the anterior lamella of the upper lid (skin, orbicularis, orbital septum and preaponeurotic fat).
Position of the Upper Lid and Its Eyelid Crease
Depending on the tilt of the face, there is an observable variance in the apparent height of the upper lid crease. Most individuals with an upper eyelid crease will show the crease optimally in a straight-ahead gaze position ( Figure 19-2 ).
Visual Axis Angle (Vax)
Downgaze ( Figure 19-3 )
In downgaze, the inferior rectus and superior oblique muscles contract while the superior rectus and levator muscle relax, stretching the latter to its longest length. For a person who has a natural crease, downgaze results in the shallowing or disappearance of the upper crease, though there is still a faint skin line that is observable on its skin.
Upgaze ( Figure 19-4 )
The crease is deepest when the upper eyelids are open and looking upward maximally – where the levator muscle is presumably maximally contracted and at its shortest length. The angle of upgaze as measured from horizontal can be designated as a positive (+) Vax (Vax = patient’s visual axis angle, relative to the horizontal axis).