Eyes are the windows of the soul and you can see what a person is up to by looking into his eyes. Hence, it is important to have clean eyesight. In yoga, trataka is a technique devised by the ancient sages to improve eyesight. It is a shuddhikriya or a purification process to cleanse the eyesight and help in the silencing of the mind in concentration.
Sit with your back straight. Keep your eyes fixed on an object without winking till tears start streaming down your face. The small object can be the flame of an oil lamp, or an image or a picture or the letter 'AUM". This object should be placed in the line of sight at a distance of about four to six feet. You can also do this kriya without any object in front of you. Having an object is not necessary. Just stare in front of you at the wall without moving the eyeballs or eyelids. Ensure that you stare at a certain point on the wall.
Before starting this exercise, you can start off by moving the eyes without moving the head, where you roll your eyeballs up and down, sideways and from corner to corner diagonally. Initially, you can make this movement with open eyes and then repeat them with closed eyes. This will give the requisite exercise to the eye muscles. This is then followed by trataka. Trataka makes the eyes clear, improves eyes and silences the mind. Over a period of time, you will experience the silence of the mind. If you want to meditate, start with trataka to silence the mind and then go to the meditation. This way, you will reap the benefits of meditation. Since you are exercising the eye muscles, they become stronger. You can perform this kriya daily without any harmful effects.