Hello dear, Dr KPS Gill here.
Minus numbers tells that u r Myopic. U r 21 years old, so by now the number gets stable. The options available to get rid of glasses - Contact lenses, Laser treatment.
Contact lenses r cumbersome to wear.
I ll advice go for Laser treatment, costly but safe and very helpful.
U have to undergo test before laser treatment to find out if it can be done.
Next Steps
Consult a lasik surgeon. Let me know the place, I can tell the good doctors there.