Why is one of my eyea bigger than the other?

Eyelid differences?: In most cases, when there is the appearance of one eye being bigger, there is simply a lid position difference between the two eyes. If the eyeball was truly bigger, it would likely have a dufferent glasses prescription (more nearsightedness). Things pushing the eye forward could also make it look bigger. Some examples include enlarged muscles, inflammation, tumors. I would discuss w your doc.