Drishti (IPA: [ dɽʂʈi ]; Sanskrit: दृष्टि; IAST:dṛṣṭi), or focused gaze, is a means for developing concentrated intention. It relates to the fifth limb of yoga (pratyahara) concerning sense withdrawal, as well as the sixth limb dharana relating to concentration.
The Bhrūmadhye dṛṣṭi (IPA: [ bʰɽuːmɐdʰjeː ]; Sanskrit: भ्रूमध्ये; meaning "to the middle of the eyebrows/brow"[madhye]) has the gaze set at the "third eye", which is right between the eyebrows. In order to do this, the eyes are closed half way. This purportedly stimulates the olfactory and optic nerves, consequently awakening the autonomic and central nervous systems. It sooths the cranial nerves and aids concentration, and helps awaken kundalini sakihi. It is advised that caution be taken as prolonged or incorrect practice may cause problems for the eye muscles or nervous system. Initial practice is often done for only minutes at a time, but is gradually increased to up to ten minute intervals. 
An example of a vinyasa which includes the Bhrūmadhye dṛṣṭi in its practice is Sūrya Namaskāraˌ wherein the Bhrūmadhye dṛṣṭi is used on the inhale following Uttānāsana, during Ūrdhva Mukha Śvānāsana, and again on the inhale following Adho Mukha Svānāsana (before the final Uttānāsana in the vinyasa).
The Nāsāgre dṛṣṭi (IPA: [ nɐːsɐːɡɽeː ]; Sanskrit: नासाग्रे; meaning "to the tip of the nose"[-gra][e Loc.]) has the eyes fixed on the tip of the nose. Purportedly strengthens the eye muscles. 
In Sūrya Namaskāra, Samasthitiḥ, Uttānāsana and Caturāṅga Daṇḍāsana all employ the Nāsāgra dṛṣṭi, as does the transition from Vīrabhadrāsana A to Ūrdhva Mukha Śvānāsana. . These are only some of the asanas and vinyasas in which this dṛṣṭi is used.
The Hastagrahe dṛṣṭi (IPA: [ ɦɐstɐɡrɐɦeː ]; Sanskrit: हसतग्रहे; generally meaning "the taking of the hand" or "the putting of the hand to", or (in the context of dṛṣṭi) "to the tips of the hand"[-gra][Loc. e]) invoulves looking at the (usually extended) tips or palm of the hand.
The navel is the center of focus for the Nābhicakre dṛṣṭi (IPA: [ nɐːbʰitɕ͡ɐkɽeː ]; Sanskrit: नभिचक्रे; meaning "to the (magical) navel-circle"; the first part of this compound word is "Nābhi" meaning "naval", the second part "cakra" which has come into use in English as chakra.[-e Loc.]).
The source of dṛṣṭis in yoga is limbs five and six from the eight limbs of yoga. The fifth limb of yoga pratyahara concerns sense withdrawal. To avoid the delusion and suffering caused by preoccupation with sense objects as described in the Maitri Upanishad, sense withdrawal is practiced in order to help the practitioner become "centered". According to tantric philosophy, keeping "centered" madhya will eventually suspend the mind and prana, allowing recognition of bhairava, or device consciousness.
Variation Between Styles
There may be differences between different styles regarding how dṛṣṭi is practiced and which are used for specific asanas, however dṛṣṭi is a primary part of at least the Ashtanga Yoga, Hatha Yoga, Jnana Yoga, Bhakti Yoga, and Raja Yoga traditions.
- gra means "tip(s) of", as in pādāgra (Sanskrit: पादा * ग्र: "tips of the toes").^Nasagre '^Hastagrahe '^Padayoragre
- The Sanskrit word madhye is marked indeclensible, so the Locative Case ("to") is applicable here.^Angusthamadhye '^Brumadhye
- The Locative Case (here "to") for Singular nouns ending in Masculine vowels (a/अ) become e/ए (a/अ blends with i/इ).^Nasagre '^Hastagrahe '^Nabhicakre '^Padayorage
- See pāda Sanskrit: पाद) meaninɡ "foot".^Padayorage
- The Locative Case (here "to") for Dual nouns ending in Masculine vowels (a/अ) is ayo:/अयोः.^Padayorage
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