Air

Intraoperative Descemet's detachment after the lens capsule is opened but before complete extraction of the nucleus/cortex can be challenging.

Aborting surgery can cause severe phacoantigenic uveitis whereas continuing with surgery risks extension and/or avulsion of the detached Descemet's membrane (DM). Jacob described a technique that we termed as air-assisted cataract extraction (ACE) for managing such a situation.

This technique was first used in a 45-year-old patient who had presented with a white cataract, extensive circumferential peripheral anterior synechiae, elevated IOP, and a thinned, old ectatic superior scleral patch graft. Cataract surgery was started by performing circumferential synechiolysis with a blunt rod under cover of viscoelastic followed by anterior capsulotomy. At this stage, a large Descemet's detachment originating from the area of superior synechiolysis, in the form of a flap anchored on either side and extending to the pupil, was seen. Because the lens proteins were exposed to the anterior chamber, a decision was made to continue with surgery using a non-phaco extracapsular technique, and the soft nucleus was attempted to be aspirated using a Simcoe cannula. Visualization was enhanced by trypan blue staining of the detached DM and by using oblique light from a vitrectomy light pipe. The corneal epithelium was also removed to further enhance visualization. The risk for aspiration and possible avulsion of the flapping DM, however, necessitated a change in strategy.

The DM was laid back flat and then floated into position against the overlying stroma by injecting an air bubble from the opposite side. A trocar anterior chamber maintainer (ACM) was inserted via a limbal paracentesis at the clock hour from where air best supported the DM, which in this case was inferotemporal, and it was connected to low-pressure air infusion (5 mm Hg to 10 mm Hg) from a vitrectomy machine. The stream of air bubbles continuously coming out of the ACM during intracameral maneuvers helped hold the detached DM against the stroma and prevented accidental aspiration when the air infusion was on. The stream was directed so as to not interfere with visualization during surgery. The pressure was kept low enough to allow a slow, steady stream of air bubbles.

The soft nucleus and cortex were aspirated gently using a Simcoe cannula, making sure that the DM was not aspirated accidentally. Superior cortex was accessed via an inferior incision. The IOL was finally gently injected under air into the capsular bag by continuing to use the ACE technique. The anterior chamber was filled with an air bubble, and all incisions were sutured. The ectatic patch graft was then repaired by using a new scleral patch graft. At the end of surgery, 20% sulfur hexafluoride gas was used to fill the anterior chamber (Figure 1).

At 1 week postoperatively, the DM was attached, and the cornea was clear (Figure 3). However, because peripheral anterior synechiae had re-formed and IOP was elevated, the patient subsequently underwent an Ahmed glaucoma valve placement (New World Medical) in the inferonasal quadrant with the tube in a sub-iris placement.

The patient continues to do well postoperatively, and at his most recent visit, 5 years after surgery, IOP is 15 mm Hg on a combination of topical timolol 0.5% and brimonidine 0.2%. The scleral patch graft is well integrated, and he has a clear central cornea that compares favorably to the preoperative appearance (Figure 2). His spectacle corrected distance visual acuity is 6/18. Autoperimetry and retinal nerve fiber layer analysis have continued to remain stable over consequent visits.

Management of Descemet's detachment when identified in the postoperative period is done on a case-by-case basis, although various classification schemes have been proposed to help plan management. Jacob previously classified Descemet's detachment into rhegmatogenous, bullous, tractional and complex types depending on the configuration, and the most commonly seen type following cataract extraction is rhegmatogenous Descemet's detachment. When recognized intraoperatively at the end of surgery, the strategy for rhegmatogenous Descemet's detachment is clear, and depending on the type of detachment (rhegmatogenous or bullous), an air bubble is introduced into the anterior chamber for pneumodescemetopexy with or without a relaxing Descemetotomy incision. However, if the Descemet's detachment happens early during surgery after capsulorrhexis but before nucleus/cortex removal, continuing with the surgery has the risk of unintentional extension or avulsion of the Descemet's detachment during surgical maneuvers, while deferring surgery results in exposure of the lens protein to the aqueous with resultant phacoantigenic uveitis and postoperative inflammation.

Options that can be used include viscoelastic tamponade and/or transcorneal sutures to the DM. However, the former may not hold the DM up during all maneuvers and may compromise postoperative Descemet's attachment due to viscoelastic in the interface. Transcorneal sutures may be difficult and, depending on the location of the detachment, may not be possible in all cases. They may also cause stretch lines and rarely tears of the DM. Despite the sutures, some areas of the DM may still sag without support from an intracameral air bubble.

The ACE technique utilizes low-pressure air infusion delivered to the anterior chamber via an ACM to hold the detached DM up against the stroma and to prevent it from sagging. The air infusion comes via the fluid-air exchange system of a vitrectomy machine or via air infusion mechanisms present in newer phaco machines. We have been using the fish tank aquarium connected via a Millipore filter to a rigid balanced salt solution bottle for pressurized air infusion in cataract surgeries for many years, and this system may also be used with the air pump connected via an empty bottle or directly to the ACM through a Millipore filter for delivering air to the anterior chamber at a low pressure. The ACE technique has the advantage of holding the DM up against the stroma, and it may be used alone, as we did, or in combination with other techniques such as soft shell or transcorneal sutures.

An early Descemet's detachment often requires familiarity with conversion to extracapsular surgery as the relatively higher vacuum employed with the phaco and irrigation/aspiration (I/A) probes may cause accidental extension or avulsion of the detached DM. This continues to be the case for the ACE technique as well. If converting, the phaco incision is closed, and a fresh extracapsular limbal incision is made. Alternately, the same phaco incision may be extended with attendant risk for greater postoperative astigmatism. In our case, the nucleus was soft and could be aspirated out, but with harder nuclei, superior relaxing incisions may be made on the rhexis followed by hydrodissection of the superior pole out of the bag, followed by visco-expressing the nucleus out of the limbal section. Cortex aspiration is preferably done after applying sutures to get a closed system. At the end of surgery, a tight air bubble in the anterior chamber with slightly raised IOP for a short time enhances DM adhesion. Intracameral long-acting gas in the postoperative period further helps reattachment. An inferior peripheral iridectomy should be done if a large air bubble is left in the anterior chamber.

A disadvantage of the ACE technique is the need for specialized machines, although these machines are generally available in most operating room setups. Visualization with the air bubbles streaming out of the ACM may be distracting, but keeping the stream at a sufficiently low pressure and appropriate direction allows surgery to be continued while the DM is held upward. In addition, surgery needs to be done with low vacuum, and we prefer continuing I/A with the Simcoe cannula once the nucleus is extracted. A slow and steady stream of bubbles was obtained by us at an air pressure between 5 mm Hg to 10 mm Hg; however, this also depends on the suction applied via the Simcoe cannula. We did not use an I/A probe for cortex aspiration because of the risk for rapid occurrence of unexpected events, but the possibility exists of using it together with a higher pressure of air infusion such that a continuous stream of air bubbles is formed, thereby holding up the detached DM.

We described a rescue technique for intraoperative Descemet's detachment that we termed as air-assisted cataract extraction. Low-pressure air infusion is used in this technique to hold the detached DM against the overlying stroma while surgery continues, preferably with conversion to extracapsular cataract extraction. The air is supplied through an ACM connected to a sterile air supply system such as a vitrectomy machine, newer phaco machine or other system. The ACM is directed to the suitable quadrant, and air pressure is set to obtain a continuous slow and steady stream of air bubbles. The ACE technique can be used in isolation or combined with other described techniques for early intraoperative Descemet's detachment occurring after capsulotomy but before removing the nucleus and/or cortex.