One eye bigger then the other? (Photo)

It appears that you have proptosis of your left eye. Please see an oculofacial plastic surgeon and this needs to be completely worked up. Number one cause of unilateral proptosis is thyroid disorders. 

Your eyes, size and whether there is an underlying problem other than asymmetry is impossible to be determined by a picture.  You are best served by getting a thorough evaluation by an ovule plastic surgeon or ophthalmologist. See your primary docto if needed for discussion and referral.  

Thank you for the question and photo. It is not possible to evaluate your eyes from the provided photo. There could be medical conditions causing your problem. You should make s consultation with an Oculoplastic Surgeon for a comprehensive evaluation and possible medical work up. Good luck.

This can be a difficult thing to judge in a two dimensional photograph.  Certain conditions such as thyroid problems can make one of the eyes to bulge and cause asymmetry.  Your best bet would be to make an appointment with a board certified ophthalmologist to assess the health of your eyes and consider referral to an oculoplastic surgeon and/or endocrinologist for further testing.  It is likely that the asymmetry is just who you are since we all have some degree of differences from one side to the other.  Good luck!

This is normal. Everyone has a "big eye" and a "small eye" It  may increase as you age. It  can be exacerbated by ptosis or drooping of the upper eyelid. This could be corrected with blepharoplasty surgery. 

It is normal to not be totally symmetric. We are always our worse critic and this asymmetry is most likely only apparent to you. Dean Vistnes.