1. Congenital factor: heredity. The child was born with ptosis. Because 2-4 years old is the golden period of vision development, 4-6 years old is the late period of vision development, and 6-8 years old is the slow period of vision development. If it is amblyopia caused by ptosis after 8 years old, it is generally incurable at this time. Therefore, children with congenital ptosis are advised to undergo surgery before the age of 3 to ensure the normal development of vision;

2, acquired factors: mainly seen in facial paralysis, trauma and so on. If the fan is blown excessively, it will cause facial paralysis, leading to ptosis on one side and even eyelid dysfunction;

3. Pseudoptosis: caused by edema of one eye, mainly eyelid allergy, improper medication, endocrine disorders, etc.