Why is one of my eyelids bigger than the other? Is there something wrong? How can I get this fixed? (Photo)

Many different situations can lead to uneven eyelids. Some of these can be treated non-surgically and conservatively, even using some very advanced injection techniques with filler or very precise placement of Botox. Some situations truly do require surgery to resolve. 
It is important that you seek a consultation with an eyelid expert to delineate the exact cause and treatment options.
To ensure you are receiving the highest level of care, seek out a modernly trained, new-school dermatologic surgeon, oculoplastic surgeon, facial plastic surgeon or plastic surgeon who is board certified and fellowship trained in one of these "core four" cosmetic specialties. Membership in organizations like the American Academy of Facial Plastic and Reconstructive Surgery help to identify a highly trained surgeon.
Cameron Chesnut
#realself500 Physician

Your pictures clearly demonstrate bilateral eyelid ptosis which is worse on the right than on the left side. This occurs because the muscles that elevate the eyelid becomes weakened or detached from their insertion into the eyelid. When this happens, the eyelid develops the droopy appearance that's noted in your pictures. Eyelid ptosis can cause visual field obstruction and significant functional impairment. For this reason, eyelid ptosis should be repaired whenever possible.Eyelid ptosis can be repaired under general or local anesthesia. The procedure is relatively simple and associated with high success rates.If you're concerned about eyelid ptosis, it's important to consult a board certified plastic surgeon with experience in this area. This surgeon should be able to formulate a treatment plan that addresses your anatomic findings and achieves your aesthetic goals.

As the other surgeons have pointed out, you have a weakness in the muscle that opens the right eye. With adjustment, your crease size should level out and any wrinkles you may have over the right eye will improve (although the brow will drop a bit). In many cases, it's best to do both eyes to maximize symmetry.