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Reduction of incision size represents only one of many advantages. . . . The crucial difference is not the size of the incision; it is the separation of inflow and outflow.
In a recent letter to the editor of the Journal of Cataract and Refractive Surgery, Steve Arshinoff, MD, of Toronto, points out the incorrect application of several terms used to describe cataract extraction by means of two paracentesis-type incisions.1
For example, he rightly notes that virtually all cataract surgeons use two hands during surgery, and therefore practice a "bimanual" technique. He also eschews all relative terms describing incision size, since yesterday's small incision size rapidly becomes today's large incision size, and "micro" will always connote "smaller than anything else, except nano."
Takayuki Akahoshi, MD, of Japan,recently reported coaxial cataract extraction and IOL insertion through a 2-mm incision.2 Using a flared phaco tip and a small-diameter sleeve, he described pre-chopping and extracting the cataract, and then introducing a single-piece AcrySof IOL through the unenlarged incision by placing the insertion cartridge tip just at the edge of the incision and pushing the IOL through with the plunger. He bills this method as the "sayonara" technique, since he says it will allow surgeons to say "sayonara, bimanual."
The underlying assumption, that BMMI phaco is only about incision size, demonstrates a superficial understanding of BMMI phaco that relates directly to the unfortunate nomenclature that Dr. Arshinoff has criticized.
Only one aspect
In actual fact, reduction of incision size represents only one of many advantages that make BMMI a superior technique. The crucial difference is not the size of the incision; it is the separation of inflow and outflow. We believe that the benefits of this fluidic paradigm shift include greater flexibility, improved control, and better outcomes. At the same time, we recognize the significant role that the introduction of micro-pulsed ultrasound energy (WhiteStar technology, Advanced Medical Optics) has played in setting the stage for bare-needle phacoemulsification. The use of extremely short pulses of ultrasound energy with a variable duty cycle initially allowed safe BMMI phaco through elimination of the risk of thermal injury to the cornea.
Separation of irrigation from the aspirating phaco needle allows for improved followability by avoiding competing currents at the tip of the needle. In some instances, the irrigation flow from the second handpiece can be used as an adjunctive surgical device-flushing nuclear pieces from the angle or loosening epinuclear or cortical material from the capsular bag. In refractive lens exchange the lens material may be washed completely out of the bag and extracted with aspiration and vacuum only, so that no ultrasound is used and no instrument enters the endocapsular space, increasing the safety profile of this demanding procedure. The flow of fluid from the open end of an irrigator represents a very gentle instrument that can mobilize material without trauma to delicate intraocular structures.