One eye is big and one eye is small, the common clinical causes include: heredity, ptosis, orbital swelling, eye trauma, eye local inflammation and other causes. 1. There is no organic lesion in the eye, but one eye is big and the other is small due to heredity. 2. Congenital ptosis or acquired ptosis due to motor nerve palsy, myasthenia gravis, etc., one eye is big and one eye is small. 3. Orbital swelling causes the eyeball of one eye to protrude outward, and one eye will be big and one eye will be small. 4. Traumatic injury to the eye may result in subcutaneous bruising and swelling, which may lead to the appearance of one large eye and one small eye. 5. Localized inflammation of the eye, such as blepharitis, can easily lead to redness and swelling of the eyelid, which may result in the appearance of one large eye and one small eye. It is recommended that patients seek medical attention to clarify the exact cause.