How much filler would I need per eye to treat my tear troughs? (Photos)

Thank you for your question and for submitting your photos.  The amount of filler you need really depends on a variety of factors, including your specific facial anatomy and bone structure, the thickness of your skin, the extent of your volume loss, and your aesthetic goals.  I also find that many patients with prominent tear troughs often benefit from fillers in the cheeks as well - deep injections on the cheekbones actually help lift the whole cheek and the tear troughs, minimizing the amount of filler that needs to be injected directly under the eyes. I think is generally best to start conservatively in the tear troughs, with 1 syringe per treatment session.  It's always much easier to add filler with time than it is to remove any unwanted product.  The tear troughs and under eyes are among most complex areas to inject with filler, and require a great deal of expertise.  Filler injections here should really only be performed by experienced cosmetic dermatologists or plastic surgeons.  Best of luck!

When it comes to dermal fillers under the eye, I find it very rare to need over 1 syringe, or 1cc, of filler. When I do need more than that, it's typically because the cheek is significantly sunken in due to weight-loss or advanced aging. Neither of those appear to be the case here.
You are young, your skin quality appears pretty good for the under eye, and you have a very distinct issue with volume loss that doesn't appear to be widespread. I think you're the perfect candidate for under eye fillers and it would be very easy to make you very happy with that treatment.
One tip I do have: consider requesting Restylane Refyne (I believe it's called Emervel Classic in Europe) as the filler used. It's a different kind of dermal filler than previous products, and will provide a smooth result that move naturally and lasts much longer than other fillers.