What causes one eyelid to droop like Diane left eye?

Ptosis, or drooping of the upper eyelid, can have several causes, including:

Muscle weakness: The levator palpebrae superioris muscle is responsible for lifting the upper eyelid. If this muscle is weak, the eyelid may droop. Muscle weakness can be caused by a variety of factors, including aging, nerve damage, and certain medical conditions.

Nerve damage: The oculomotor nerve controls the movement of the levator palpebrae superioris muscle. If this nerve is damaged, it can cause ptosis. Nerve damage can be caused by trauma, infection, or certain medical conditions.

Mechanical problems: Ptosis can also be caused by mechanical problems, such as a tumor or cyst that is pressing on the levator palpebrae superioris muscle.

Congenital ptosis: Some people are born with ptosis. This type of ptosis is usually caused by a developmental problem with the levator palpebrae superioris muscle.

In Diane's case, the drooping of her left eyelid may be due to any of the above causes. A thorough evaluation by an ophthalmologist or neurologist is necessary to determine the exact cause of her ptosis and the appropriate treatment.