The image is the figure of a blind man, groping along in the darkness. This is symbolic of our situation in the world, stumbling blindly from birth to death, ignorant of our true situation.
The ignorance of beings is a thick veil that obscures clear seeing of reality. It comes in two forms; dullness and confusion. The dull mind is weighted down by the darkness of unknowing into stupidity and torpor. The confused mind wanders in false passages, it is the mind shackled and burdened with false views.
The dependent origination is here represented as a wheel, to show that it is without beginning or end. Ignorance may be taken as a starting point only in that it is so fundamental as a root of defilement; this makes it a convenient starting point for an exposition of the teaching. But in reality, ignorance itself is like all worldly phenomena, it arises from prior causes and not otherwise.
In the case of human life, the trauma of death followed by birth causes us to forget what we have learnt in our previous lifetimes. Only a residue remains; we come into the world ignorant and mostly beings remain so, weighted down by dullness or confused by strange teachings and theories.