1. **Congenital Ptosis**: Present at birth, often due to improper development of the levator muscle responsible for lifting the eyelid.
2. **Neurological Causes**: Disorders affecting the nerves that control the eyelid muscles, such as:
- Horner's syndrome
- Third cranial nerve palsy
- Myasthenia gravis
3. **Muscular Causes**: Conditions affecting the muscles, such as:
- Muscular dystrophy
- Myopathies
4. **Mechanical Causes**: Physical factors preventing the eyelid from opening properly, such as:
- Tumors
- Swelling
- Excess skin
5. **Trauma**: Injury to the eyelid or surrounding structures can lead to ptosis.
6. **Aging**: Natural aging can cause weakening of the eyelid muscles or the tendons that support them.
7. **Aponeurotic Ptosis**: Often age-related, where the tendon of the levator muscle stretches or detaches.