作成者はProfessor Uday Devgan MD, renowned Los Angeles cataract surgeon, teaches the Best Techniques for Cataract Surgery という属性の眼科医。 Vivityは2年前から使い込んでる由で、かなり実践的なこと言ってます。 (口語を意訳しました)
The emergent wavefront mimics the anterior lens surface shape after light passes through the surface transition elements. The wavefront is delayed when it passes through the central part of the surface transition elements and advanced when passing outside of the central part. The delayed part of the wavefront travels slower and focuses closer to form an image towards the near end of the extension and the advanced part of the wavefront travels faster and focuses further to form an image at the far end of the extension. As the wavefront propagates, it collapses down resulting in the wavefront being stretched forward and backward thereby creating a continuous extended focal range.