The 3rd eye of knowledge is to do with realisation, knowing the 3 aspects of time, the subtle worlds, but most important, the true natural original self, which is where the 3rd eye lives.
The 3rd eye is based on the intellect, that which retains knowledge and developes wizdom.
A deep Realisation is a true vision compared to visual things.
Seeing through the eye of wizdom than the physical eyes.
To see or not to see, this is the question.
Love