It is a common phenomenon in those of Asian descent for the upper eyelid crease to fluctuate throughout the day or to change in height, shape, depth, or completeness under the influence of both known and unknown environmental factors, including alterations in humidity, salt intake, alcohol consumption, fluid retention, dehydration, crying, sleep deprivation, physical exertion, and so on.
In some people, a natural crease in one eyelid may remain consistently present while the other crease seems to be unpredictably everchanging and to come and go at will.
This phenomenon can be expressed variably in different people. For instance, some experience the presence of a noticeable crease only in the morning, while others may experience better definition in the afternoon or evening.
The reasons for such inconsistency are not well understood. Since fat can swell with fluid retention and shrink with fluid restriction, one's state of hydration may likely play a role by allowing the orbital fat to shift in position throughout the day. If orbital fat were to descend lower into the eyelid due to swelling or retract out of the eyelid due to shrinkage, crease expression might be, respectively, either hindered or enhanced.
It is not at all rare for patients seeking double eyelid surgery with the goal of enhancing the height of their low creases to also request crease stabilization for one or both of the eyelids.
If crease height and shape are already satisfactory, surgery may even be undertaken for the sole purpose of stabilization.
An erratic crease may be permanently stabilized by employing a combination of techniques similar to those used in incisional double eyelid surgery, particularly deep fixation and/or the excision of a small strip of orbicularis muscle from the area just above the superior tarsal border.
While the mechanism of action is theoretical, it is likely that such maneuvers create a physical "blockade" that prevents easy fat movement.
If a natural crease is already satisfactory, crease stabilization can be achieved without altering its present shape and height.
The surgical techniques mentioned above are discussed and demonstrated elsewhere on this site.