Aberrant Regeneration of the Pupil

Aberrant regeneration represents a misdirected growth of nerves to the iris dilator or sphincter (or their respective autonomic ganglion) following injury to both the axons and glial support tissue of the nerve. In response to the disruption of axons, the surrounding glial elements (Schwann cells) produce neurotropins (nerve growth factors). The result is profuse axonal sprouting from the surviving proximal nerve endings. The sprouting axons make their way through the disrupted glial support tissue or scar and become misdirected back into the wrong glial tubes. This is why the presence of aberrant regeneration almost always implies that damage to the nerve was from structural disruption due to trauma or compression (and not due to ischemia). As the misdirected axon sprouts continue their growth down the distal portion of the nerve they end up re-innervating the wrong target tissue.