The article by Burkholder and associates is a useful addition to the literature in that it highlights the relatively uncommon complication of inadvertent trypan blue staining of the posterior capsule and adds to the list of risk factors (that includes traumatic cataract and pseudoexfoliation) the use of iris hooks. We first noted this phenomenon in the second case we treated, and although it made the surgery more difficult, the advantage of being able to see the anterior capsule clearly throughout the surgery far outweighed the disadvantage of a reduced red reflex.
In our minimalist 1-step technique of trypan blue application to the anterior capsule, aqueous humor initially is allowed to exit the anterior chamber, which consequently shallows, and the resulting pupil block confines the dye to the anterior capsule, when a moderate volume of dye is instilled. We believe that this is a critical step in dye application. An ophthalmic viscosurgical device then is used to flush dye-stained aqueous from the anterior chamber, circumventing the need for anterior chamber washout.
It would be useful to know the precise method of insertion of iris hooks because this does not seem to be described in the article. When iris hooks first arrived in Australia, there was some departmental discussion regarding how they should best be applied. The consensus was that hook ports should be made with a 15-degree blade just posterior and perpendicular to the surface of the surgical limbus, care being taken not to penetrate the iris. This sometimes makes passage of the hooks to the pupil margin more difficult because the hook shaft now needs to bend to be in the iris plain; this passage can be facilitated by a Sinskey hook. However, the resultant vector forces are such that the iris is pulled both peripherally and also posteriorly, rather than anteriorly. In this way, the iris remains opposed to the anterior capsule, eliminating or at least reducing the flow of fluid from the anterior chamber into the posterior segment. By magnifying the images in Figure 1 of the article, it appears that the hook ports have been made in a more horizontal direction with a consequent lifting of the iris off the anterior capsule plain. This would facilitate the passage of dye under the iris and into the posterior segment, thereby facilitating staining of the posterior capsule. This configuration also can result in shallowing of the anterior chamber, because during phacoemulsification, infusate can force the iris anteriorly. This is particularly problematic in cases where there is zonular dialysis and the anterior vitreous can be more directly hydrated. Furthermore, in an age of phacoemulsification chopping and femtosecond nucleus fragmentation, this configuration could facilitate the transport of small nuclear fragments into the posterior chamber and beyond. This method of vertical incisions for iris hook insertion also is useful in dealing with floppy irides, because the vector forces help to push the iris posteriorly.
If, in the cases reported, iris hooks were inserted horizontally, then by altering the insertion technique, this complication of capsular dye use can be rendered even more uncommon. Furthermore, the technique of vertical hook insertion has other advantages that add an extra safety factor to managing small pupil cases.