What is the best way to treat deep malar/mid-cheek grooves? (Photos)

For unique cases where a variety of modalities could be used to treat the condition, I would suggest an in person or virtual consultation to develop a custom and effective treatment plan. It is difficult to precisely define the best option without collecting the same information. I suggest reaching out to an expert for a consultation with surgical and non-surgical methods to get a comprehensive option. Best, Dr. Emer.

The pictures you provided show a degree of volume loss in the midface. High density HA fillers would be my first choice for building up deeper volume in this area. The goal would not be to make you cheeks look bigger, but to fill in the areas of existing volume loss. If you have tried HA fillers and are looking for something more permanent you could consider fillers like sculptra or even fat transfer using your own naturally occurring body fat. There is also some degree of cheek descent. So you could also consider radiofrequency tightening like thermage. All the best! 

These midface cheek grooves can be difficult to treat. I find that filler to replace lost cheek volume gives the best result. I do not recommend injecting filler superficially into the groove because it can lead to chronic swelling making things look worse.