Swami Kriyananda wrote in the Art and Science of Raja Yoga,
The position of the eyes suggests the general portion of the brain in which the consciousness is centered.
In particular, when the mind slips toward subconsciousness and the energy becomes centered in the lower brain, the eyes tend to look downward; when one is involved in the world, or otherwise active on the conscious level, the energy becomes centered more in the mid-brain, and the eyes tend more naturally to look straight ahead; and when one enters a state of superconsciousness, the eyes are drawn automatically to gaze upward.
The Spiritual Eye, or Christ Center is located at the point between the eyebrows. It is the seat of spiritual awakening. When all of our energy becomes centered there, enlightenment occurs.
When seen perfectly, The Spiritual Eye consists of a silvery-white five-pointed star, surrounded by a field of deep indigo blue, which in turn is framed by a ring of gold.
It is extremely important to have your eyes turned upward to the Spiritual Eye in meditation. Focusing there helps you attune to, and magnetically draw, the highest states of consciousness. (You should remember, however, that although the eyes are physically gazing at the Spiritual Eye during your practice of Hong-Sau, your concentration should be on your breath).
If you feel tension when you look at the Spiritual Eye, try this advice from Swami Kriyananda:
Raise your gaze upward – not crossing the eyes, but focusing them on a point somewhat beyond the forehead at about the distance of your thumb when you hold your arm extended above you. The height of your thumb should be level with the top of your head.
The important thing is that your attention, not your eyes, be focused on that point in the forehead. Don’t try forcibly to bring your eyes to a focus, but gaze mentally at that point, and let the Spiritual Eye draw you into Itself.
If you notice that your mind has wandered off Hong-Sau mantra, you may also notice that your eyes are no longer looking upward. When this happens, raise your eyes again and refocus them on the Spiritual Eye, and your mind, on the breath. In time, you will feel a pull of energy within the forehead, and it will become easier for you to keep your eyes focused upwards.
Once you end your practice of Hong-Sau, you should spend some time focusing on the Spiritual Eye, whether you can see the light there or visualize it.
If you see the light, calmly offer yourself into it. If you don’t see the light, pray deeply, “Reveal Thyself… Reveal Thyself.”
Even if you don’t see the light, you will feel your consciousness uplifted. In his book The New Path, Swami Kriyananda writes:
Through concentration on the spiritual eye, the consciousness gradually becomes attuned to the subtle rate of vibration of this light. At last one’s consciousness, too, takes on the quality of light.