The iris is a kinetic and flowing structure that moves during pupil constriction and dilation. But the iris can also move quickly during surgery in response to fluid flow and pressure gradients. One of the challenging issues is when the iris prolapses through the phaco incision during cataract surgery.
There are multiple factors which contribute to iris prolapse including poor ciliary muscle tone, sub-optimal incision architecture, and a high pressure behind the iris. Patients who take tamsulosin (Flomax) fall into the category of poor ciliary muscle tone and are particularly prone to iris prolapse.
In the case shown here, the iris prolapses at the end of surgery once the IOL is in the capsular bag and the viscoelastic has been evacuated. The iris has poor tone from the tamsulosin use and there is a pressure gradient with higher pressure behind the iris than in front of it. Even with the properly constructed incision, the iris partially prolapses at the end of the case.
Fixing this issue requires two steps: First, release the pressure gradient by flattening the anterior chamber and allowing fluid egress. This allows the iris to retract back inside the anterior chamber. Second, seal the incision with hydration to prevent more prolapse and inflate the anterior chamber via the paracentesis incision
Click below to learn this important technique to fix iris prolapse: