When we get tired then it may happen that one eye seems to be smaller than other.

Thank you for your question. It would be helpful if you could post some pictures. It is very typical for other eyes to change shape when tired, one may become heavier and droopier than the other therefore appearing smaller.  If this happens only when you are tired, I would suggest it not being a problem, however if this is not the case, please make sure you find a reputable and qualified eye surgeon who can assess you properly to give you a realistic idea of what the cause is and what outcome can be achieved.  Upper Eyelid Surgery, where extra skin and fat on the upper eyelid can cause the eyes to feel and look tired. Taken to the extreme, the extra skin can hang so much that it can hamper your vision and cause discomfort. Eyelid surgery combined with Eyebag Removal can effectively reduce the excess skin from the upper and lower eyelids to leave you with wider more youthful looking eyes. All The Best

Thank you for sharing your question. It is very common for individuals to notice one or both eyelids dropping when tired. If this is the only time you have a droopy eyelid, you should ignore it. Otherwise, see an experienced eyelid surgeon for evaluation and guidance.  Good luck,

That's a great question! It would be helpful to see pictures, as there could be many causes.  One of the more common causes is a mild stretching of the tissues that raise the eyelid,  so you "work" a little harder on that side.  As the day goes on, it shows a little more from fatigue.  This can be corrected by upper lid surgery.