The mechanism of injury for AION used to be quite controversial. However, the experts in the field (neuro-ophthalmologists) have come to a consensus that most cases involve the convergence of two problems. The first is a predisposition in the form of a type of optic disc shape. The optic disc is the most anterior (forward) portion of the optic nerve, the bundle of nerves that carries the visual signals from the eye to the brain. This optic nerve must penetrate through the wall of the eye, and the hole to accommodate this is usually 20-30% larger than the nerve diameter. Hence there is extra space that acts as a margin of error. But some patients have no such margin. Their optic disc appears “crowded” when seen by ophthalmoscopy. Nonetheless, most patients with this optic disc shape see well all of their lives.