When we insert the IOL, sometimes viscoelastic will be lost via the main incision. This can happen if we gape the incision when we use the chopper or second instrument to fully place the optic and haptics within the capsular bag. Since we are typically using a cohesive viscoelastic to fill the capsular bag, distorting the incision will allow much of it to escape.
Once the anterior segment has been flattened, and the capsular bag collapses, it becomes more difficult to dial the IOL haptics into the capsular bag. At this point, you must avoid damaging the capsular bag with the IOL or the second instrument.
The safest option is to re-inflate the eye before attempting further manipulation of the IOL. The easiest is to use more of the viscoelastic as shown in this video. Another option is to use an infusion of balanced salt solution via the I/A probe to pressurize and inflate the eye while the chopper is used via the paracentesis to adjust the IOL position.
Click below to see why re-inflating the eye is critical before adjusting the IOL: