Trocar anterior chamber maintainer facilitates ocular surgeries

The maintainer allows easy, atraumatic transconjunctival entry into the anterior segment.

Issue: January 2017

ByAmar Agarwal, MS, FRCS, FRCOphth

ByPriya Narang, MS

Self-sealing wounds are the most desirable hallmark of any intraocular surgery. Controlled access to intraocular segment structures without running the risk of hypotony is the prime concern of all surgeons. Anterior chamber maintainers and trocar cannulas are the most common methods employed for infusion by anterior segment and posterior segment surgeons, respectively.

The introduction of the trocar cannula was a monumental advance in ophthalmology because it allowed, for the first time, controlled access to the posterior segment of the eye, and currently it is an integral part of modern pars plana vitrectomy for maintaining infusion in the eye. A 23-gauge (0.6 mm), 25-gauge (0.5 mm) or 27-gauge (0.4 mm) entry does not require an incision of the conjunctiva and Tenon’s layer to expose the sclera. Instead, trocars are placed through the conjunctiva and sclera to afford access to the vitreous and to maintain infusion in the eye.

Taking into consideration the advantages of a trocar system, we employed a method of introducing the trocar cannula for maintenance of the anterior chamber, an idea originally conceived by Agarwal, with advantages that would be availed by anterior segment surgeons with equal ease and élan. We call this T-ACM (trocar anterior chamber maintainer).

Surgical procedure

Figure 1. A 23-gauge trocar cannula system.

Figure 2. Trocar needle being inserted obliquely in the sclera about 1 mm away from the limbus.

Figure 3. The direction of the trocar needle is turned perpendicular toward the globe.

Figure 4. The trocar is inserted in the eye so that it enters the eye in front of the iris.

Figure 5. The trocar is removed, and the cannula is fixed in place.

Figure 6. The cannula is positioned in place, and it snugly fits the limbal area.

Figure 7. The infusion line is attached to the cannula, and the T-ACM is in place.

Figure 8. The cannula is removed, and no active leakage is observed. The anterior chamber is well maintained.

Before cannula insertion, the conjunctiva is displaced with a cotton tip to keep the conjunctival puncture away from the scleral-limbal wound. The cannula (on a trocar) is inserted into the limbus approximately 1 mm away (Figures 1 and 2), usually at a 45° angle (depending on gauge) and parallel to the limbus. The trocar is then turned directly toward the center of the globe (Figure 3) so that it enters the anterior chamber in front of the iris tissue (Figure 4). It is advanced until the hub of the cannula is flush with the sclera. The trocar is then removed (Figure 5), leaving the cannula in place (Figure 6). This maneuver allows a longer scleral wound and carries a lower risk of wound leakage. The infusion line is attached to the stent of the cannula (Figure 7), and the infusion is turned on.

At the end of the surgical procedure, the surgeon withdraws the T-ACM, and because the wound is self-sealing, no leakage is observed (Figure 8).

Advantages

The advantage of using a T-ACM is that it allows an easy and atraumatic transconjunctival entry into the anterior segment. It also allows better endurance and ability to create auto-sealing ports. Utilization of valved trocars can offer better control of IOP and eye outflow during the surgery, although we have not yet exploited this option in our patients.

T-ACM can also be employed for maintaining continuous air-fluid infusion in the eye in cases of corneal endothelial keratoplasty. This can prevent repeated shallowing and reforming of the anterior chamber and minimize the risk of iris damage, miosis and lens damage in phakic eye procedures. Some surgeons even prefer using vitrectomy air exchange pumps for the same.

The other advantages of T-ACM are induction of less astigmatism because a corneal side-port incision is prevented, along with prevention of overcrowding of the anterior chamber and cornea in complicated cases, allowing more working space for the surgeon. Combined anterior segment and posterior segment surgeries can be undertaken with T-ACM in place.

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Discussion

The maintenance of a deep anterior chamber is a prerequisite for a safe anterior segment surgery. An anterior chamber maintainer helps prevent anterior chamber collapse apart from serving as an important tool during IOL insertion, post-IOL insertion maneuvers, vitrectomy or secondary IOL implantation, obviating the need for use of an ophthalmic viscosurgical device. Fluid is the natural milieu of the anterior segment, and its use during surgery does not disturb any of the anatomical relationships in the eye.

Surgical wound creation for introduction of an anterior chamber maintainer necessitates the use of a paracentesis wound with a side-port incision in the peripheral cornea. The anterior chamber maintainer must be exactly the right size, and the knife must be withdrawn along the tract of entry because any sideways movement during entry or withdrawal will produce an incision that is too large and the anterior chamber maintainer wound will leak. Suturing an incision is often required to prevent postop hypotony and to minimize the continuous leak and the induced postop astigmatism. All of these shortcomings are outweighed by the use of T-ACM.

Conclusion

In T-ACM, an oblique incision parallel to the limbus displaces the circumferentially oriented scleral fibers laterally, rather than cutting them. Creation of a biplanar incision seals the wound perfectly. The use of T-ACM has applications that, in our opinion, may facilitate some complex ophthalmic surgeries. A word of caution is to choose an appropriate distance from the limbus while introducing a T-ACM in a phakic eye so as to curtail the possibility of hitting the transparent lens.

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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.

Disclosures: Agarwal and Narang report no relevant financial disclosures.