Hello there.
Dr KPS Gill here.
-2.5 means u have Myopia.
Options to correct are
1. Spectacles
2. Contact lenses
3. Laser treatment (LASIK).
If u want to get rid of glasses, go to some Lasik surgeon and get the laser treatment.
U r 21 years old and by now ur number gets stable. U have to undergo few tests before the laser treatment.
Next Steps
Only way to remove number, LASIK surgery