40 year old female - horizontal crease between eyes. What can be done to remove it permanently? (Photo)

In my experience, this problem is not that uncommon. When the combination of Botox and filler alone have not yielded gratifying results (although they typically do when combined and when Botox is employed by an experienced injector in the appropriate concentration and amount and the proper filler injected in an appropriate fashion), then subcision, a simple and relatively inexpensive technique for permanently elevating all kinds of indentations. Surgical excision runs the risk for the subsequent development of stretch scars and tram track stitch marks. You would be wise to consult with an experienced, board certified cosmetic dermatologist and best of luck.

The horizontal crease between your eyes, also known as the glabellar line, is indeed caused by the repetitive contraction of the procerus and corrugator supercilii muscles. While Botox and fillers can significantly reduce the appearance of this line, they cannot completely eliminate it.
For a more permanent solution, a surgical procedure called a Corrugator Supercilii Muscle Resection (CSMR) might be considered. This procedure involves removing or weakening the muscles that cause the crease, thereby reducing its appearance. However, this is a significant surgical procedure and not without risks. Potential side effects include asymmetry, changes in sensation, and possible changes in the ability to express emotions through facial movements.