The various causes of ptosis are as follows:

• Ageing- in some people the muscle that lifts the upper eyelid slips back with age and the eyelid droops
• Congenital- It is mainly due to developmental anomaly of the lid lifting muscle.
• Trauma- Trauma to the eye can damage or disinsert the muscle controlling the height of the eyelid.

• Nerve palsy- One of the nerves controls the muscle that lifts the lid, it also controls the eye movements. In nerve palsy the lid droops along with a squinting eye. Ptosis is also seen in a neural condition called Horner’s syndrome. Both these conditions require immediate and detailed examination by an eye specialist. It can be due to diabetes, tumor or trauma.
• Eye surgery- Cataract surgery can rarely lead to this complication.
• Myasthenia gravis- It leads to temporary, often severe, drooping of one or both eyelids usually in the evenings. The height of the lids are completely normal in the mornings or after some rest. This is associated with muscle weakness and fatigue. It is treatable with medications.

Ptosis is generally corrected surgically when it is cosmetically or vision disturbing.