Double-infusion cannula technique minimizes complications, optimizes outcomes

The technique provides internal globe stability, prevents pressure fluctuations, and enhances graft stability and adherence.

Issue: June 10, 2017

ByAmar Agarwal, MS, FRCS, FRCOphth

ByPriya Narang, MS

Endothelial keratoplasty helps to restore the sanctity of the corneal endothelium from both a functional and structural aspect. Graft tissue adherence to the corneal surface is a matter of concern in eyes with pseudophakic bullous keratopathy or aphakia that need either an IOL explantation or an IOL placement, respectively, along with an endothelial keratoplasty procedure. Hypotony and graft adherence are the two major concerns in eyes undergoing secondary IOL placement with an endothelial keratoplasty procedure.

The double-infusion cannula technique (DICT) is a method in which two infusion cannulas are introduced inside the eye. The primary one is introduced for fluid infusion at the pars plana level and the second one at the level of the limbus as a trocar anterior chamber maintainer (T-ACM) that is employed for air infusion inside the eye. DICT is aimed at solving both issues simultaneously, thereby decreasing the chances of complications and optimizing surgical outcomes.

Method

The initial procedure comprises making two partial-thickness scleral flaps 180° opposite to each other followed by introduction of a fluid infusion cannula at the pars plana site about 3 mm to 3.5 mm away from the limbus. The glued IOL procedure is performed, and the IOL is securely tucked into the intrascleral pockets (Figures 1a to 1f).

Figure 1. Placement of pars plana fluid infusion. A case of pseudophakic bullous keratopathy (a). Superficial keratectomy is performed, and the epithelium is debrided, which helps to enhance the visibility of intraocular structures. Two partial-thickness scleral flaps are made 180° opposite to each other for the glued IOL procedure (b). A trocar cannula introduced at the pars plana level for fluid infusion (c). A scleral tunnel is made, and the anterior chamber IOL is explanted (d). A three-piece foldable IOL is introduced into the anterior chamber, and the tip of the leading haptic is held with glued IOL forceps introduced from the left sclerotomy site (e). Both haptics are externalized from their respective sclerotomy sites (f).

Figure 2. Placement of the second infusion cannula. Pupilloplasty is performed with the single-pass four-throw technique (a). A PDEK graft is prepared. A type 2 bubble is created, and the edge of the bubble is punctured with a side-port blade (b). A T-ACM is introduced into the eye. The T-ACM enters the eye in front of the iris tissue into the anterior chamber (c). The T-ACM is connected to the Constellation machine, air infusion is switched on, and descemetorhexis is performed (d). Air infusion is stopped, and the donor graft is injected inside the anterior chamber. Once the graft has unrolled, pressurized air is introduced at 50 mm Hg for 30 to 45 seconds (e). Fibrin glue is applied, and the scleral flaps are sealed (f).

Figure 3. Preoperative and postoperative images of DICT. Preoperative image with pseudophakic bullous keratopathy (a). Postoperative image at 3-week follow-up after DICT (b).

Once the IOL is fixed, a T-ACM is introduced inside the eye at a distance of 0.5 mm away from the limbus, creating a biplanar wound. The T-ACM is introduced in a way that it enters the eye in front of the iris tissue into the anterior chamber. The T-ACM is attached to the tubing of the Constellation machine (Alcon), and air infusion is switched on. Descemetorhexis is performed, and the donor graft for pre-Descemet’s endothelial keratoplasty is loaded onto the cartridge of a foldable IOL and is injected inside the anterior chamber. The graft is gently unfolded by tapping the anterior surface of the cornea, and once it is totally unfolded, air infusion is switched on with a pressure of 50 mm Hg for 30 to 45 seconds (Figures 2a to 2e). After this, the pressurized air infusion is stopped, and no specific attempt to burp the air from the anterior chamber is attempted or is needed because the posterior infusion cannula replaces some amount of air with fluid in a controlled way. The pars plana infusion cannula is removed, followed by the T-ACM. Pressure is applied over the entry site with a cotton tip applicator to avoid egress of air or fluid from the eye. Fibrin glue is then applied to seal the scleral flaps and the conjunctival wounds (Figure 2f).

After placing the first infusion cannula and performing secondary IOL glued fixation, the eye gets effectively compartmentalized into the anterior and posterior chambers. The fluid infusion helps to maintain the tonicity of the eye and prevents the globe from collapsing. Pressurized air infusion in the eye from the T-ACM helps to vault the graft and adhere it to the recipient bed.

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Performing DICT has various advantages such as no seepage of air into the vitreous cavity in both the intraoperative and postoperative periods because the posterior chamber is continuously maintained with fluid seeping into the eye from the pars plana infusion cannula. This helps in graft adherence. Moreover, after descemetorhexis, air infusion from the T-ACM is stopped, and the anterior chamber does not collapse because gentle fluid seepage occurs into the anterior chamber from the fluid infusion from the posterior vitreous cavity. This facilitates graft unfolding and maneuvering. Pressurized air infusion is switched on only when the entire graft has unfolded. DICT provides internal globe stability, prevents pressure fluctuations, and enhances graft stability and adherence, thereby making the surgery more surgeon dependent.

For more information:
Amar Agarwal, MS, FRCS, FRCOphth, is director of Dr. Agarwal’s Eye Hospital and Eye Research Centre. Agarwal is the author of several books published by SLACK Incorporated, publisher of Ocular Surgery News, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery and Presbyopia: A Surgical Textbook. He can be reached at 19 Cathedral Road, Chennai 600 086, India; email: dragarwal@vsnl.com; website: www.dragarwal.com.
Priya Narang, MS, is the director of Narang Eye Care & Laser Centre, Ahmedabad, India. She can be reached at email: narangpriya19@gmail.com.

Disclosure: The authors report no relevant financial disclosures.