According to Svatmarama (author of the old Hatha Yoga Pradipika) Trataka, concentrated gazing, “eradicates all diseases of the eyes, fatigue and sloth”. It also facilitates the one pointed focus of the mind and is very soothing and is said that it can help us to develop our intuitive powers .
Trataka is best practiced with a candle, placed on a table at eye level, in a dark room. In a sitting pose at a distance of about two to three feet, gaze unblinking upon the centre the flame. Ideally the flame should not flicker at all. Stare for as long as possible, even if only for a few moments. Tears may be shed.
With practice, you may gradually increase your gazing time from five to ten minutes. When you need to close your eyes an after image may appear. Observe it intently. When it disappears, open your eyes and begin a new round of gazing. If the candle gives you the finger, you will know you have gone too far! Joking aside Trataka can also be practiced on the moon or upon the light within another's eyes.