It is essential to understand the anatomy in detail, the normal physiology and pathophysiology of the lower eyelid to properly correct an involution entropion surgically. The fact that 50% of involutional entropion causes show an actual defect (dehiscence or complete detachment) of the retractor aponeurosis of the lower eyelid is important. The surgeon must be cognizant of the high rate of occurrence of these defects and look for them during the surgical repair. The direct external approach of the imbrication procedure makes it easy to identify these aponeurotic retractor defects. The pathophysiologic changes can vary with each case and are as follows involutional changes (attenuation, dehiscence, detachment) taking place in the lower lid retractors; atony of the lateral and medial canthal tendons may be present and must be recognized; enophthalmus of the aging is present; the septal oribicularis loses it firm attachment to the orbital septum. It is paramount that the pathophysiologic changes present in each case be recognized and surgically corrected to prevent recurrences.