How could I improve my negative canthal tilt? (Photo)

To create more almond shaped eyes, it requires elevation of the lower eyelid plus canthoplasty, not just canthoplasty. See following link and video.

However, you have upper eyelid ptosis and both of these issues need to be addressed.  Do not assume the reconstructive oculoplastic surgeons are the same as surgeons who do aesthetic reconstructive surgery.  Multiple opinions are helpful and in my opinion you will need to travel to get the best possible result.

Thank you for your photo and question.  An oculoplastic procedure called a canthoplasty can be done to correct a negative canthal tilt.  This is a sophisticated, and delicate procedure which can change eyelid shape and show only be done plan experienced oculoplastic or plastic surgeon who specializes in eyelid surgery. For more information please read below: