How to get rid deep tear trough and sunken eyes?

Fillers are great for treatment of tear troughs. It will probably take some time for you to gain the weight. You can elect to have filler injected now or wait until you put on the weight. The fillers disappear usually by 9 months. Good luck!

Thanks for the question, I like fillers for these areas, I will typically use a very light filler and I typically am very conservative to start, nothing looks worse than overdone eyes, if patients need more we add more 2 or 3 weeks later

If you are underweight, putting on some pounds will likely improve the hollowing of your lower lids although its not possible to know to what degree or even give you an educated guess without photos or an exam.  Regardless, you should try to get to a healthy weight and then worry about your eyelid appearance secondarily.  All the best!

not necessarily. Often times, volume loss in the under eye region with deep tear troughs may be genetic and/or age-related. Non-invasive treatments include soft tissue fillers (see link below). Surgical treatments include volume-enhancing implants or lower eyelid surgery with fat repositioning. The latter procedure is best if you have lower eyelid bags in addition to the deep tear troughs and essentially moves the fat from the bag into the tear trough.

If you are underweight by 20 kgs and you notice a tear trough deformity, go ahead and gain the 20 kgs that will bring your weight back upto normal, then you can evaluate your facial volume to see if your concerns still  exist.