Ageing of the lower eyelid makes it loose and unstable and predisposes the lower eyelid to outward sagging or drooping (ectropion). It's important to evaluate the risk profile of the lower eyelid prior to any surgical procedure to minimise risk of ectropion.
The lack of muscle tone of the orbicularis muscle causes excessive tearing - a feature seen in patients with Ectropion. Ectropion can be caused by ageing changes (involutional ectropion) or scar induced ectropion (cicatricial ectropion). Involutional ectropion is due to excessive laxity while cicatricial ectropion is due to excessive tightness and scar contracture. Common causes of cicatricial ectropion are scarring following cosmetic surgery, skin cancer surgery, laser eyelid surgery or burns. Surgery involves removal of scar tissue and introduction of healthy tissue as skin grafts, flaps or spacer grafts. Treating involutional ectropion involves resuspension and tightening of the lower eyelid sling.
The lower eyelid is best described as a hammock. For the hammock to be suspended at the right tension multiple factors have to be considered. The lower lid is no different. Ageing changes affect the tension of the two anchor points as well as the amount of stretch in the hammock (eyelid). If the eyelid is deemed to be at risk for ectropion prior to surgery then proactively correcting the changes will avoid developing an ectropion post-operatively.