There are two different levels of connection to the infinite Light and spiritual energy of the Upper Worlds.
"The Vision" מחזה - the lower level
"Yud Hei Vav Hei" יהוה - the higher level
Before he underwent the ritual of circumcision, Abraham could only connect to and experience the level of The vision. After circumcision, however, Abraham was able to attain the level of the Yud Hei Vav Hei יהוה.
An ability to connect to a higher realm of Light - the level of Yud Hei Vav Hei - is made available to us through forces that are unlocked in this mystical passage. We are drawing upon the purification power of circumcision and Abraham's elevated consciousness to ascend to this exalted realm.