Conditions such as aging, prior surgery or trauma can lead to weakening of the lower eyelid. If the lower eyelid weakens enough, the lid may rotate outward. This condition is known as ectropion. Ectropion can cause chronic eye irritation and tearing because the eye is constantly exposed to air.
Surgery to correct ectropion generally involves tightening the lower eyelid, known as canthoplasty. Severe cases may also require elevating the cheek to reduce the gravitational pull of the cheek on the lower lid.