TROCAR ANTERIOR CHAMBER MAINTAINER

Dhivya Ashok Kumar, MD(AIIMS), FICO, FAICO, FRCS; Athiya Agarwal, MD, DO; and Amar Agarwal, MS, FRCS, FRCOphth

Anterior Chamber Maintainer

Maintenance of a deep anterior chamber is a prerequisite for safe, smooth performance of any intraocular surgery. This prevents inadvertent and harmful contact of intraocular instruments with the corneal endothelium. It is for this reason that ophthalmic viscosurgical device was developed, and this was a major breakthrough for all anterior segment intraocular surgeries.^1–3 In 1987, Blumenthal devised a simple and practical method for maintaining the anterior chamber with a 21-gauge scalp vein set. He called this device an anterior chamber maintainer (ACM). There have been a variety of subsequent modifications to the ACM to suit different surgical applications.^4–6 The ACM has to be introduced via a corneal paracentesis incision using a side port or a microvitreoretinal blade. Too large an incision often causes the ACM to be expelled from the eye, while too small an incision necessitates further enlargement. We introduced an improved technique that incorporates a trocar, which is typically used in posterior segment surgeries. This trocar anterior chamber maintainer (TACM; Mastel Precision) is inserted into the anterior chamber via the limbus in order to maintain adequate infusion into the eye during intraocular maneuvers.⁷

Trocar Anterior Chamber Maintainer

The TACM consists of a 25-gauge stainless needle and cannula. The inner trocar guide needle slides directly through the cornea. Once it is withdrawn, it leaves the blunt infusion cannula in place (Figure 66-1). The TACM device comes as a surgical package consisting of the trocar needle and cannula with handle, the protective cover, and the infusion line tubing (Figure 66-2).

TECHNIQUE OF INSERTION

A scleral entry point 0.5 mm posterior to the limbus is measured and marked using a vernier caliper. The trocar needle is introduced at a 45-degree angle to the sclera and parallel to the limbus. Rather than performing a conjunctival peritomy, the overlying conjunctiva is displaced by the trocar needle prior to entry (Figure 66-3). The trocar is then redirected 90 degrees perpendicular to the limbus and toward the anterior chamber so that the trocar enters the anterior chamber just in front of the iris. The cannula is advanced until it is flush with the surface of the sclera. The trocar is then withdrawn, leaving the cannula in place. The infusion line is then attached to the hub of the cannula and the infusion turned on. One can alternatively make a straight entry into the sclera above the iris.

INDICATIONS FOR THE TROCAR ANTERIOR CHAMBER MAINTAINER

The TACM can be used to provide continuous infusion for any complicated anterior segment procedure requiring fluid infusion and chamber maintenance. Common indications include posterior capsule tear requiring anterior vitrectomy, zonular dialysis, a capsule defect requiring glued intraocular lens (IOL) implantation (Figure 66-4), and shallow anterior chamber traumatic hyphema washout. The TACM can be used with trauma cases such as those presenting with multiple corneal injuries, hyphema requiring washout, lens damage, and zonular weakness. It can be in use in small eyes such as nanophthalmos or microcornea where an ACM is required to deal with deficient capsule integrity. It can be used with repositioning of a decentered posterior chamber IOL (Figure 66-5) or for IOL exchange. The TACM can be electively used to maintain anterior chamber depth in endothelial keratoplasty procedures, such as pre-Descemet’s endothelial keratoplasty (PDEK; Figures 66-6 and 66-7) or Descemet’s membrane endothelial keratoplasty (DMEK).⁸ For PDEK, the TACM can also provide continuous infusion of air for the technique of air-assisted PDEK. Selective cases of iris repair and single-pass four-throw pupilloplasty will also be facilitated by using a TACM for chamber stability.

POTENTIAL BENEFITS OF THE TROCAR ANTERIOR CHAMBER MAINTAINER

The major advantage of the TACM is that it allows an easy, atraumatic, transconjunctival entry into the anterior segment that will be self-sealing. This ACM will not become dislodged as easily as other designs. A properly configured ACM improves access to and control of the intraocular environment and avoids the problem of hypotony. The TACM can also be used to deliver and maintain continuous air or fluid infusion in the eye in cases of corneal endothelial keratoplasty. This can minimize the risk of iris damage, miosis, and lens damage in phakic eye procedures by preventing repetitive shallowing and deepening of the anterior chamber. Some surgeons even prefer using vitrectomy air exchange pumps for the same purpose.⁹ Other advantages of the TACM include the reduction of induced astigmatism and maximizing the surgical working space. The TACM can be used for continuous air pressure maintenance during air pump–assisted endothelial keratoplasty and to produce internal tamponade in case of chamber hemorrhage. Finally, combined anterior and posterior segment surgeries can be performed using the TACM.

WOUND ARCHITECTURE IN TROCAR ANTERIOR CHAMBER MAINTAINER

A Fourier-domain optical coherence tomography study of these TACM incisions demonstrated proper wound apposition and stability with complete healing by 1 month. In a short pilot study, we evaluated 5 eyes of 5 patients in whom the TACM was used for varied indications. The mean diameter (Figure 66-8) of the internal incision ostium was 36.8 ± 40.9 μm. The mean width of the visible tunnel in the corneal stroma was 27.0 ± 37.1 μm. The mean length of the tunnel was 786.4 ± 412.9 μm. Two out of 5 eyes had a localized Descemet’s detachment on postoperative day 1. None of the patients had wound leak on day 1, and all Descemet’s membrane detachments spontaneously reattached. From postoperative day 1 to 7 there was no significant change in sizes of the internal ostium (P = .109), the external ostium (P = .109), and the tunnel width (P = .180). However significant reduction in corneal thickness was noted during this period (P = .043) as would be expected.

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