Computer assisted cataract surgery with toric intraocular lens implantation
Markerless alignment system for treating corneal astigmatism
Cataract surgery is one of the most frequently performed surgeries worldwide. The main aim of cataract surgery is to restore visual function by removing the optically degraded crystalline lens using phacoemulsification and to implant a clear artificial intraocular lens (IOL).
In the past decade, technological advances in IOL optics, as well as in the procedures and tools used in cataract surgery, have improved significantly with increasing predictability of the refractive correction.1,2
Likewise, patient expectations are more and more demanding with regard to spectacle independence after surgery. Sophisticated IOL designs have therefore been developed to provide a complete visual restoration after cataract surgery, including toric IOLs that allow a satisfactory refractive correction in eyes with significant amounts of corneal astigmatism.3
The accurate alignment of a toric IOL is essential to achieve the intended astigmatism correction.4 A toric IOL misalignment of 11.5º could lead to a residual astigmatism that is 40% of the initial astigmatic power, and 3º of misalignment might result in values that are 10% of the initial power.4
In a standard setting, the cornea is marked manually before surgery to identify the steep meridian using a manual marking instrument. During surgery, the axis of the implanted IOL is rotated to the position of the marks. This manoeuvre requires surgical experience, can be biased by ocular cyclorotation, and is time consuming. For this reason, new systems allowing a digital control of toric IOL alignment without manual marking have been developed, such as the Callisto eye Z Align from Carl Zeiss Meditec.