"Theoretically this practice [staring at a flame] works toward the decalcification of the
pineal gland, considered by some to be the master gland of the body. The pineal gland ossifies around the age of puberty to 16 years of age, after which many modern scientists and biologists consider it a secondary gland. However in yoga science, this gland is said to rule all the others and that it is also related to the awakening of very high spiritual understanding in the individual. Since it is considered to be sensitive to light, the practice of flame watching acts to decalcify the pineal, allowing it to function properly for both its material and more subtle purposes."

Taken from: Daily Health in the Indian Ayurvedic System by Dr. Aja Thomas
To read the entire article, go to: http://www.skepticfiles.org/mys1/ayurdoc.htm