Making the phaco incision is one of the most critical steps in cataract surgery. A well-constructed incision will seal without leaks, induce a predictable amount of astigmatism, and will provide excellent access to remove the cataract and insert the IOL.
As we have shown in many videos, one of the main concepts for incision construction is having good architecture with the roof of the incision balanced with the floor. Of course, placement, tunnel length, and other factors come into play, but paramount is the incision balance.
In the correct tri-planar incision (green diagram above), there are three planes when we look at the incision in side profile: the incision starts parallel to the iris then the angle changes to go into the corneal stroma and create the desired tunnel length. Then the blade is brought parallel to the iris again in order to enter the anterior chamber.
In the “dimple down” mistake (red diagram above), the initial plane starts out very shallow, then the angle is shifted to achieve the desired tunnel length. Finally, to enter the anterior chamber, the surgeon must abruptly change the angle to enter the anterior chamber. This “dimple down” technique will result in an imbalanced incision with a thin roof and thick floor, which will look like a chevron when viewed at the slit lamp or surgical microscope.
Click below to learn how to make a correct three-plane incision: