Do we know at what age trolls are considered adults? At what age do they leave the planet and at what age do their eyes start filling up?

The exact age is unknown. At 7 Sweeps- 15-16 Years old, you go through your Rites of Maturation. Given the age range, it’d seem this is your initiation into the Work Force, and then, possibly somewhere between the 8.5-10 Sweeps (18-21 Years), you’re considered an Adult, begin your Ordeals, and get sent off-world. What either Rites of Maturation or Ordeals may involve, is unknown.