It seems the ancient sages who practiced yoga thought of everything, even where you look when practicing yoga poses. Drishti may be considered a point of focus involving vision, however, the impact of Drishtis is said to be internal. The idea behind practicing Drishtis is to deepen the concentration of the mind.
The effect of casting your gaze toward nine distinct points of reference can aid in yoga posture biomechanics. For instance, when practicing standing forward bends gazing toward the navel will offer several benefits. With the chin slightly tucked the back of the neck opens releasing any pressure that might be exerted on the vertebral arteries that are responsible for approximately 50% of blood flow to the brain. If the back of the head is pulling up and the chin lifted away from the collar bones, which is often the natural instinct, blood flow through these arteries can be compromised causing dizziness. The Drishti where the gaze point is to the naval is advised in the practice of standing forward bending yoga postures to avoid dizziness.
I remember David Williams telling a story a decade ago at the Ashtanga Mela held at the Kripalu Centre in Lennox Massachusetts about Free Divers who use no equipment when deep sea diving. The Free Divers were mentioning to David that they have to keep their chin tucked throughout a dive, and that if they even lifted the chin for a second the blood flow in the arteries would be reduced and they would pass out and drown. David replied that this was a similar to tucking the chin when practicing certain yoga techniques.
Beyond the physical attributes Drishtis can offer, attention may be directed to energetic centers of the subtle body. A prime example of this would be the practice of gazing to the third eye Drishti. It is purported that focusing at this point between the eye brows can develop a strong sense of intuition. In Paramahansa Yogananda’s ‘Autobiography of a Yogi’ the third eye is described with an introductory quote from the Gospel of Matthew. “If therefore thine eye be single, thy whole body shall be filled with light. – Matthew 6:22. During deep meditation, the single or spiritual eye becomes visible within the central part of the forehead. This omniscient eye is variously referred to in scriptures as the third eye, the star of the East, the inner eye, the dove descending from heaven, the eye of Shiva, the eye of intuition, etc…”
Of course I am not able to substantiate the above claim in scientific terms but find the theory of great interest. In a more verifiable sense focusing on the third eye Drishti when practicing certain yoga poses will strengthen concentration. When attention is placed on the space between the eyebrows, the visualization of metaphorical third eye becomes an internal process.
Along with the naval and third eye, other Drishtis include: thumb, tip of the nose, hand, far to the right, far to the left, toes, and upward. The wide variety of gaze focal points can offer a sort of mix and match depending on injuries or medical conditions that yoga practitioners are working with. Instead of rigidly applying a particular Drishti to a specific yoga posture, it is much more effective to create an exercise prescription through proper application of the Drishti based on the needs of the individual. In the yoga world there is a deep-seeded belief that each yoga pose has a single appointed Drishti, but this is a narrow view and can lead to injury.
An example of a Drishti gone wrong would be the insistence on applying the traditional gaze point for triangle pose if the yoga practitioner has neck or shoulder problems. By turning the head to gaze past the hand of a vertically extended arm, torsional forces will likely exacerbate a neck or shoulder injury. I ask students who have neck problems to leave their arm that would normally extend upward along the side body and look forward or down depending on what feels better.
Drishti should enhance a yoga posture and not be the source of injury. As with all practice yoga postures should feel comfortable. Resist falling into the trap of thinking you are doing it wrong simply because you switched out one Drishti for another. Historically Drishtis were practiced separately from yoga postures, so to insist specific Drishtis need be applied to particular poses seems to ignore the context from where we find their original application.