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BLOG: Double-infusion cannula technique
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The double-infusion cannula technique, or DICT, involves placement of two infusion cannulas for the purpose of secondary IOL fixation along with endothelial keratoplasty in cases with aphakic or pseudophakic bullous keratopathy, or PBK.
The primary trocar cannula that is placed at the pars plana for fluid infusion helps to maintain globe integrity and its tonicity. The second trocar cannula is placed as a trocar anterior chamber maintainer (T-ACM) and is introduced into the anterior chamber from a distance of 0.5 mm away from the limbus, creating a biplanar wound architecture. The T-ACM is introduced in a way that it enters the eye in front of the iris tissue into the anterior chamber.
The specific purpose of placing two infusion cannulas is well explained and formulated in a way that the posterior infusion cannula at the pars plana site helps to infuse fluid in to the eye continuously during the initial process of secondary IOL fixation by the glued technique, whereas the second cannula placed anteriorly is used only for air infusion inside the anterior chamber, which facilitates the descemetorhexis procedure and graft adherence to the recipient corneal bed. After the graft is unfolded, pressurized air is introduced and a pressure of 50 mm Hg is maintained for 30 to 45 seconds. Due to the presence of fluid infusion in the vitreous cavity, air from the anterior chamber does not seep in posteriorly, and this, along with pressurized infusion, promotes the graft to attach and adhere to the corneal bed. Air infusion is stopped when the graft is injected and unfolded inside the eye. At this juncture, gentle fluid seepage into the anterior chamber from the vitreous cavity helps to maintain the required anterior chamber depth that is instrumental in graft unfolding.
The video showcases the technique of DICT in a case of PBK due to an anterior chamber IOL. The IOL is explanted followed by glued IOL fixation with the placement of the infusion cannula at the pars plana. In this case, because the pupil is irregular, a single-pass four-throw pupilloplasty is performed to narrow down the pupillary aperture. The second infusion cannula is then placed for air infusion in to the eye, and pre-Descemet’s endothelial keratoplasty is performed. DICT provides internal globe stability, prevents pressure fluctuations, and enhances graft stability and adherence, thereby making the surgery more surgeon dependent. Amar Agarwal, MS, FRCS, FRCOphth, has graciously contributed the video to this blog, which explains the procedure in detail.