For most cases a coaxial arrangement of both the phaco and irrigation / aspiration (I/A) handpieces works very well. However, for vitrectomy (both anterior/limbal and posterior/pars plana), a bimanual set up works better since it allows us to separate the infusion from the aspiration. In some cases, bimanual irrigation/aspiration is very helpful in removing cortical cataract material.
In this case, the patient has a history of tamsulosin (Flomax) use and the resultant floppy iris syndrome and poorly dilating pupil. The I/A handpiece is the disposable Transformer model from Alcon which allows use as both coaxial and bimanual. Traditional bimanual I/A requires two paracenteses which one is used for the irrigation and the other for aspiration, while the main incision is not used for cortex removal. The handpieces can then be swapped to allow the surgeon easy 360° access to the entire capsular bag, including the sub-incisional area. The Transformer I/A handpiece first functions as a traditional coaxial I/A via the main incision. It can then be pulled apart so that the infusion still goes through the main incision, but the aspiration tip is now place via the paracentesis incision.
In this case of a smaller pupil, it is helpful to have the bulkier infusion tip above the iris while the smaller aspiration tip is placed within the capsular bag. The inflow of fluid keeps the iris in position and helps prevent floppiness and prolapse.
Click below for a floppy iris case where bimanual irrigation / aspiration is used:
(I have no financial interest in this product. I use it occasionally.)