This summarizing chapter covers the author’s current concept of various anatomical factors that contribute to or adversely affect a crease formation. Familiar drawings will help illustrate the concepts and factors that have been discussed in the advanced chapters, and how these can be applied clinically.
I am continually fascinated by the unpredictability of the eyelid crease; some of its factors can be represented by the expression above. This chapter will reveal the significance of each of these factors, and we will return to this expression again at the end.
C = ∫ ( Latt , LC , F , afi , pf , gz , h ) ( s , m , f , ( − ) Vax , eypo , BrPt , BrOA , h + , h − )
What Is an Upper Eyelid Crease?
Let us start gently as an initial attempt to answer the question posed here. An upper eyelid crease can be described as an inward folding of the upper lid skin above the eyelid margin, and is positioned along the superior tarsal border.
In common usage, the lid crease is less anatomically defined, and it can be confused to include anything from a faint wrinkle above the lid margin where tight skin becomes looser, to a well-formed crease invagination along the superior tarsal border, to describing what in actuality is the upper eyelid sulcus. I have personal experiences of well-educated patients describing what to them constitutes an eyelid crease: from anything that occasionally appears in the morning, the evening, after a drink or two, after crying, after reading, after they turn 17, 30 or whatever age, or after a voluntary attempt using a co-contracting stare-and-frown maneuver (staring activates the levator through the third nerve, frowning tightens the periorbital orbicularis oculi and frontalis muscle, mediated through the seventh nerve), to a fold that forms as a result of where they applied their lid crease glue, tape or special fiber string. These various positions are seldom the correct location for an anatomically natural crease.
Most of the above do not appear natural, and therefore it is just as important for us to try to define what are the characteristics of a natural crease.
Firstly, a natural crease is present shortly after birth, is seen in most head positions and is effortless in its formation. It may be of different shape and height in different ethnicity, but should share these common characteristics.
Secondly, a true eyelid crease has a faint crease line on the skin which can be seen when the upper lid margin is turned down (or when the eyelid margins oppose together); its location typically corresponds to the upper boundary of the superior tarsus. Anatomically it corresponds to where the distal fibers of the levator aponeurosis terminate into the pretarsal section of orbicularis oculi or skin along the superior tarsal border. Recent scientific studies using more refined electron microscopy were able to see attachment of aponeurotic fibers actually terminating under the skin where the natural crease line forms, confirming some previous assumptions. When the eyelids are open, the ‘reinforced’ pretarsal platform of tarsal plate/orbicularis muscle and attached pretarsal skin will vector upward as a unit against a passive preseptal skin–orbicularis: the invagination is the crease, the overhang is the eyelid fold. The interface for this to occur is the preaponeurotic fat, which I conceptually describe as the glide zone.
Thirdly, a true crease is a dynamic crease; it has the characteristic of fading on downgaze (when the levator of the lid is relaxed as the inferior rectus contracts to roll the globe downward), unlike what one sees with an arbitrarily anchored eyelid crease indentation or one induced through compression (encircling, buried) sutures.
Most individuals who have an upper eyelid crease will manifest the full crease in a straight-ahead gaze position ( Figure 22-1 ).
In downgaze, the inferior rectus and superior oblique muscles contract while the superior rectus and levator muscles relax (the relaxed levator is at its longest length in downgaze). Downgaze results in the shallowing or disappearance of the upper crease ( Figure 22-2 ) in a person who is born with a crease, though there is still a faint skin line.
Head Tilt and the Eyelid Crease
Why is there a difference in apparent depth to the upper eyelid crease depending on the frontal posture of the face?
The crease is most apparent when the eyelids are open and the eyes are looking straight upward – where the levator muscle is presumably maximally contracted (and at its shortest length). Compare this to when the person tilts the head’s vertex backward slightly (in a slight chin-forward position) but still maintains forward horizontal gaze; as far as the eyeball is concerned, this is similar to a downgaze and therefore the crease is less manifested and observable here.
Height of Crease
What about the ‘width’ of the crease? (It should be measured and named as the ‘height’ of the crease, from ciliary margin to the crease indentation with the lids closed.) This is the anatomic crease height ( Figure 22-3 ).
Is the crease the observable step-in between the larger fold of skin above the crease and the exposed pretarsal skin with the vectored-in lid crease hidden beneath it?
The observed apparent crease height as measured from the eyelash border will be 1–3 mm narrower than if measured all the way towards the hidden apex of the crease, which is the tilted crease height (Tch) . The eyelid crease should be defined by the faint crease line we see with the lids closed (in the absence of acquired ptosis), and when measured should seem to correspond to the superior tarsal border’s central measured height; we shall denote this as the anatomic crease height .
(Note that the tilted crease height is the vertical component of the sloped pretarsal segment ( Figure 22-4 ). When there is an overhanging lid fold of x mm, the apparent crease height is the vertical component of Tch minus the obstructing (shielding) portion of the lid fold of x mm, where x may be 1–3 mm.)
Anatomic crease height > Tilted crease height ( Tch ) > Apparent crease height