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.

Based on this one photograph, your right eye seems to have a mild ptosis (or droopiness).  One sided ptosis, as you have, is usually caused by a levator aponeurosis dehiscence - a tiny piece of tissue that normally helps to hold the eyelid open has weakened or come detached from the cartilage of the eyelid (tarsal plate).  If this is the problem, we can perform surgery to correct the dehiscence and restore your normal eyelid appearance.  There are other forms and causes of ptosis, however, which is why an examination and full history by a facial plastic surgeon, occuloplastic surgeon, or plastic surgeon is key in determining if further testing is required and what surgery should be performed.    

Both eyelids are heavy or ptotic.  However, you make extra effort to open the right eye.  This means that you are activating the right brow and frontalis muscle more than the left side.  This is why it does not look like you have a fold on the right side.  Repairing the eyelid ptosis will allow the brow to relax down and will restore the right upper eyelid fold.  This generally is best accomplished with an anterior levator ptosis procedure even if you respond to the neosynephirine drop test. Study my website for examples of how this type of repair is done.  Glasses help hide things.

You do have eyelid asymmetry.It would also help to see your complete face. Surgery can be done to even your eyelid
heights. Please see an Oculoplastic surgeon.

Zoe3193, Almost every patient I see has asymmetry of a part of their face; many times including the eyelid area and brow. From your photos I can not tell if your brows are symmetric and/or well placed. That would be the place to start. See several experience facial plastic specialists who have good photos and experience. See my site as a good example. Do your homework and you will be allright! Good luck!

The double fold of the right upper eyelid may indicate a levator dehiscence which means the tendon that lifts your upper lid may have partially pulled out or the muscle is weak. See an occuloplastic surgeon or plastic surgeon who speializes in eyelid surgery for an exam and diagnosis. A repair is possible

In your photograph, it appears that your right upper eyelid is taller than your left. There also appears to be a muscle imbalance with your right eye out of alignment with your left.It would be helpful to see your forehead, as well. If you are raising your right brow more than your left, that could account for the eyelid asymmetry.You mention that your eye fatigues: it is important to know exactly what that means. Does the eyelid droop more at the end of the day?These many factors are best sorted out in a proper in-office consultation and evaluation to determine the causes of your eyelid asymmetry and then consider treatment options.