Why Are my Eyes Different Sizes?

Hi Friend, thanks for sharing your story and the photograph. 
It looks like your left eyebrow sits a little higher than the right. I like to think of the eyebrows as the curtain rod, and the eyelids as the curtains. If the eyelids are drooping then the brow's compensate to keep the lids from blocking your vision. 
You'll want to visit a plastic surgeon and make sure to check out their website to make sure they know how to take care of eyelids because this is a finesse procedure and every millimeter counts! I can't wait to see you get better!

Your eyebrows are in different positions. the left one is higher than the right one. It is possible that you are compensating for a left eyelid drooping by raising your eyebrow on the left side a bit higher. It would be best to see a plastic surgeon to examine you closely in person, stabilize your forehead, etc. and see how the eyebrows respond in that setting. If you have unilateral ptosis of the eyelids, you may need that fixed to have your eyebrows end up in more similar position. But that's not the only option. It really depends on the cause and your anatomy.
-David Mattos, New York Plastic Surgical Group

Asymmetry between the two eyes can have various causes. Some of these causes include:
difference in upper eyelid positiondroopy eyelid (eyelid ptosis), eyelid retraction, etc. difference in lower eyelid positionreverse eyelid ptosis, eyelid retraction, etc. difference in eyeball positionsunken eye (enophthalmos, hypoglobus), bulging eye (proptosis, exophthalmos), etc. orbital asymmetryfacial asymmetryetc. 
The treatment depends on what is causing your issues. You should see an Oculoplastic surgeon and Ophthalmologist for a complete evaluation.