I am 39 years old with loss of facial volume, sagging cheeks and deep tear troughs, what can I do to correct this? (photos)

Hello, Happy New Year! Thank you for your question. 39 is not too young to start being proactive about your skin care and preventative options to keep you looking your best. 
With your concerns and looking at your photos, a combination treatment would address your needs best. 
For crows feet, Botox is still the most effective. By relaxing the muscle around your eyes, the wrinkles are smoothed and your eyes appear more open and alert.
For volume loss, you would be a good candidate for filler to the cheeks and laugh lines. When we consider which filler is appropriate, we look at your bone structure, your skin elasticity, and the thickness of your skin. 
At your age, to encourage DNA renewal of your skin and to keep it plump, I recommend my patients to start on a retinol product.
There are also lasers that can be directed to the dermis (strength layer of skin) to tighten and lift to a degree but this would require an in person consultation because certain skin tones cannot be treated with lasers as this will result in hyper or hypopigmentation.
May sure you consult with a qualified injector or physician who can answer your questions and give you a personalized plan to get you looking refreshed.
I hope this helps! - Dr. Leong

I think combination treatments work best when it comes to antiaging. In your case, a filler such as Restylane Lyft or Sculptra could be injected into the midface to correct age related volume loss and to lift the face. Newer generation flexible gel hyaluronic acid fillers like Restylane Refyne and Restylane Defyne could then be injected into the laugh lines. Wrinkle relaxers like Botox or Dysport could help with the lines around the eyes. Skin tightening with the new Thermage FLX and skin surfacing with Clear + Brilliant combined with a good at home skincare regimen would round out the results.