Realistically, Nasagra Drishti is not covered under shuddhikriya. There is a shuddhikriya known as Trataka. It is useful for purification of the mind. Concentrating your eyesight on a bindu (point) without fluttering the eyelids till the eyes water is known as Trataka. Similar type of exercise of the eyes and eyesight is attempted under the process Nasagra Drishti. Hence, it is included under Nasagra Drishti.
- It is expected to keep the body pose firm and center the gaze at the tip of the nose.
- Initially, it seems difficult. So one should draw a dot (either kum kum or sandal paste) on the tip of the nose, when both the eyes can see the dot, then it can be said that the Nasagra Drishti is successfully performed.
If this drishti is to be practised, then one should sit in Padmasan. When the gaze is fixed, it can be attempted without even putting a dot on the tip of the nose. In the later stages, it can be practised even with the closed eyes. The process of gazing at the tip of the nose without fluttering the eyelids, helps to achieve the concentration of the mind.
Since the process is related to the mind and the brain, it is not to be practiced for hours together. While learning it can be performed even for a minute or two at a stretch. When it can be performed well, it may be practised for more duration. While practising dhyana, if this drishti is practised initially, then the wavering mind can be concentrated and the dhyana can be done easily.
We generally move both our eyes in a parallel fashion. If we start gazing at the right side, then both the pupils turn towards the right and we gain knowledge of the article on the right side. If one has to gaze at the tip of the nose with both the eyes, then the left pupil gazes at the right and the right at the left. Thus, the movement of both the pupils is made in opposite direction and not in a parallel manner. This creates strain on the eyes which is generally never there. The muscles are also stretched in a different manner than usual. This affects the brain. Hence, in such a drishti, the concentration of the brain is achieved fast and with more ease. So the drishti is studied with the aim of achieving concentration of the mind.
The relation of this practice is with the brain, so it should be practised carefully. It should be practised only for a short time in the initial stages and when the nervous system and the brain is accustomed to the strain, then one can increase the study. Persons suffering from the diseases of the nervous system should not practise this without expert guidance. If in Nasagra Drishti, one can see only with one eye, then it is not correct. It may cause eye problems. Also, it should not be practised wearing spectacles.
References in the ancient texts
None of the ancient texts mention this drishti. However, while describing certain asanas, it is clearly stated that the gaze should be fixed at the tip of the nose i.e. Nasagra Drishti.
The second chapter of Gherandsamhita while describing Padamsan, states that one should keep Nasagra Drishti.(Gherandsamhita 2:8).
The next shloka while describing Jalandhar Bandh also states that there should be Nasagra Drishti (Gherandsamhita 2 : 10). Also while describing Simhasan, there is a reference of Nasagra Drishti (Gherandsamhita 2 : 15). The twenty fifth shloka describes Gorakshasan, there also it is stated that there should be Nasagra Drishti. The end of this chapter which describes yogasanas, also refers to Nasagra Drishti (Gherandsamhita 2 : 45). The fifth chapter of Gherandsamhita describes pranayam, while practising Nadishuddhi Pranayam, it is stated that there should be Nasagra Drishti. (Gherandsamhita 5 : 43).
Thus, these types of references are found in the other yoga texts too. They are generally of this nature only and hence need not be separately considered.