Though most people think the best time to treat amblyopia is 8 years old, the treatment was effective on 20-year-old person. If you have a lazy eye, eye exercises is a must to treat your lazy eye. However, you should consult with your doctor.
The best time to treat lazy eyes is under 16,the earlier,the better. The chance of success will be smaller as you are already 20. But there is still hope. You can go to the specialist and have a ask. Good Luck!