Right eye has eyelid retraction (hereditary) and I'm hoping to get surgery for both eyes. Will canthoplasty help? (photos)

First, this is not lower eyelid retraction. We use the term retraction after surgery or from inflammation from thyroid related conditions like Graves' disease. That is not your situation. You have relative proptosis also known as hemiexophthalmos. Simply your cheek is not as projected enough to support the cheek and lower eyelid soft tissue. Generally lateral canthoplasty alone is not adequate for addressing your concern. An actually physical examination is needed to asses your anatomic resources. Generally using a spacer graft in conjunction with a canthoplasty is not adequate for addressing this issue. For this reason, I recommend a hand carved ePFTE orbital rim implant to support a vertical midface lift. A hard palate graft is also used behind the eyelid to gently shape the lower eyelid. I have doing this approach for over 20 years. I caution you on isolated canthoplasty with or without space material. Some of these surgeries are not sufficiently aesthetic. Please study the links I have attached below.