Is there any specific issue with your eyes or do you just want to maintain good visual health? Since you are 20 years old, you may be studying or working on the computer. Vvisual hygiene is very important. Read in good light, with sufficient distance from the computer. Take regular breaks and blink frequently to avoid eye strain and dryness. Few simple eye exercises that can be done are - eye rotations, focusing on the tip of the nose, focusing between the two eyebrows, keeping head straight and turning the glance to the left shoulder then right shoulder. Eye drops may be avoided unless there is a specific problem.

If you have been given glasses, do wear them and get your eyes checked every year. Eat balanced diet which should include green leafy vegetables, carrots, milk, proteins in the form of pulses, fruits etc. If you are working on computer for more than 2 hrs a day, then take rest by closing eyes for 20 seconds every 20 minutes.