In most cases, I like to make the phaco incision on the steep meridian of corneal astigmatism. If the patient has a mild degree of astigmatism, the incision coupled with a limbal relaxing incision can address the corneal astigmatism completely. If the patient has 1 diopter or more of pre-existing corneal astigmatism, then the phaco incision coupled with a toric IOL can be used to address the astigmatism. But why do I like to make the phaco incision on-axis when we can simply calculate its effect and use the toric IOL to address the net resultant astigmatism? And what does vector math have to do with this? Well, let me tell you about airplanes and headwinds, tailwinds, and crosswinds...
