Iris prolapse is caused by a pressure differential between the anterior chamber and the outside world. In this case, the pressure differential is caused in part by BSS from hydrodissection getting trapped behind the nucleus.
1. A smaller rhexis, combined with aggressive hydrodissection, can trap balanced salt solution (BSS) behind the lens. This can push the nucleus forward, increase anterior chamber pressure, and precipitate iris prolapse.
2. Quite simply: iris prolapse is caused by a pressure gradient between the anterior chamber and the outside world. Relieve the pressure gradient, and the iris will return back to its proper place.
3. The chopper should not sit idle. Either use the chopper to help chop or use it to help protect the capsule.
4. Come out quickly with instruments to reduce BSS outflow that re-prolapses the iris.
5. You can turn the infusion sleeve downwards to push iris out of the way while entering the eye.
6. Cohesive viscoelastic is not super helpful for pushing back the iris, as it will prolapse out easily.
7. Place a corneal suture with the eye at physiologic pressure.
Check out this article by Dr. Devgan for a more in depth discussion: