Ptosis or drooping eyelid is a disorder characterized by loosening and falling of the upper eyelid. Ptosis , also referred to as the medical term "Belpharoptosis", has different types. For example, This condition is called "unilateral ptosis" when it affects one eye and it's called "bilateral ptosis" when it affects both eyes. The excessive loose skin and eye bags in the upper eyelid are called "dermatochalasis".
Ptosis may be present at birth (congenital) or appear later in life (acquired). It can be temporary or permanent. Surgery usually is the best treatment for drooping eyelids. Ptosis surgery carried out at Tehran-Iran Noor Eye Hospital, usually involves tightening the muscle that elevates the upper eyelid (Müller or levator aponeurosis muscle).
So we conclude that ptosis may be having these characteristics:
1. It can affect one or both eyes.
2. It can be hereditary.
3. It may be congenital (presents at birth)
4. It may be acquired (appears later in life)