In patients with prior uveitis, synechiae between the iris and the anterior lens capsule can develop. These adhesions will prevent the pupil from dilating during cataract surgery and they will make it more difficult to stain the anterior lens capsule with Trypan blue dye.
You could fill the eye with viscoelastic and then perform lysis of the synechaie and then dilate or stretch the pupil, but then you would need to remove the dispersive viscoelastic in order to allow the Trypan blue dye to stain the anterior lens capsule. Then after staining, more dispersive viscoelastic would be injected into the anterior chamber and the case could proceed normally.
I have a different approach which allows just one fill of the anterior chamber using the dispersive viscoelastic. In addition, I have some pearls for dilating the pupil and then injecting triamcinolone into the anterior chamber to quell post-op inflammation.
Click below to learn how to deal with this case of Synechiae and Cataract Surgery: