The main causes of different eye sizes include physiological factors, eyelid edema, and ptosis, which should be treated as soon as they are detected. The human body is not strictly symmetrical, so it is common for two eyes to be different sizes. If the difference is more serious, it may be due to unilateral eyelid diseases, such as eyelid edema and ptosis. Eyelid edema is usually caused by blepharitis, acute dacryocystitis, or kidney disease, etc., the patient may appear eyelid subcutaneous tissue fluid accumulation, resulting in one side of the eyelid is enlarged; and ptosis is mainly due to the levator ani muscle and upper eyelid muscle dysfunction, and unilateral eyeball by the eyelid cover the manifestation of the two eyes are not the same size. If the different sizes of the eyes are more obvious or accompanied by abnormal vision and other discomforts, it is recommended to consult a doctor in time to avoid delaying the condition.