July 1, 2015
Imperative to the efficacy of all toric IOLs is the position of the IOL with regards to the intended alignment axis because every degree of misalignment leads to residual astigmatism. Misalignment of the IOL may be caused by either inaccurate placement or rotation of the IOL.
Toric IOLs represent a significant advance in achieving optimal cylindrical and spherical refractions after IOL surgery and are the preferred method for correcting pre-existing astigmatism during cataract surgery. Accurate rotational stability and axial alignment of toric IOLs are critical to the efficacy of surgery. Each degree of rotation causes an average loss of cylinder power of approximately 3%; subsequently, when an IOL rotates 30°, there is a complete change of axis with no astigmatic correction. Several studies have evaluated the rotation of toric IOLs using methods such as slit lamp estimation and digital photography, but not all of them take head tilt and cyclorotation into consideration.