I have a great educational video about spherical aberration and IOLs that is coming out in the next few weeks. But in the interim, why would we want a negative spherical aberration IOL? This patient had old LASIK with an older generation laser many years ago. That treatment induced positive spherical aberration in the cornea and by having negative spherical aberration in the IOL we can help offset that. Also, look at the pic of this Tecnis IOL — why is there a null-zone on the optic? The optic diameter is 6 mm but the actual focusing optic is only about 5 mm because of that null zone. Why? Think about the refractive index of this IOL and optic thickness and injector cartridge size… answer in the video.