Part of the “bright-eyed” lively look of youth is eye lids that are more widely open, with the upper eyelid naturally held up by the tone and function of the muscles.
With the passage of the years, generally the upper eyelid is not held up as high, so the eyes are less open. Of course, this varies a lot between people, reflecting a number of factors – such as different eye area shapes, differences in sun damage and differences in collagen and elastin properties among individuals.
One major factor that is not well known is the major impact of sustained high blood sugars on the function of the upper eyelid muscle.
This is well explained in this video by the highly respected diabetes expert, Dr. Richard K. Bernstein.