The speed at which surgery happens during phaco is directly related to the aspiration flow rate, which is measured in cc/min. When the phaco tip is unoccluded and you are bringing cataract material to it for phaco-aspiration, the speed of the fluid flow in the anterior segment is the critical parameter. The volume of the anterior chamber is about 0.25 cc and even if you include some additional volume for space within the capsular bag after partial nucleus removal, this is a small volume. When you see in the pic above that I am using a flow of 40 cc/min, this means that if the tip is not occluded, the anterior chamber will be turned over 160 times per minute. This is 2.67 times every second! With a higher flow rate of 50 cc/min, it is more than 3 times a second, whereas with a lower flow rate of 25 cc/min it is only 1.67 times a second. This is a much slower speed and it is easier for a beginning surgeon to operate in this more controlled environment.
click below to understand why the aspiration flow rate is your speed limit: