Nithyanandarajah et al.1 described a technique for sealing clear corneal incisions using a 30-gauge needle and balanced salt solution injected into the anterior stroma above the incision. I taught this specific technique to 25 residents over the past decade. The technique is based on personal communication with Jay McDonald,A who used a 30-gauge needle to deliver vancomycin into the corneal stroma by injection via radial placement of the needle into the anterior stroma. I found this method to be ergonomically challenging so began placing the needle tangential and 1.5 mm anterior to the epithelial keratome entry point over the entry into the anterior chamber. I like to place the micro-bolus at the level of mid stroma overlying the middle of the Descemet membrane incision. Entry 1.0 mm lateral to the keratome incision allows a 20- to 30-degree angle from the corneal surface to be used. Placement of the needle tip in mid stroma is key, as placement that is too shallow leads to an epithelial bulla and too deep risks Descemet detachment. It is also helpful to have the patient look away from the side of the incision to achieve an easier approach. If the initial advancement of the plunger is too easy, one is probably in the anterior chamber. If a bulla starts, we reinsert the needle with a greater angle of approach. I stop when the area of whitening reaches 1.0 mm in circumference around the needle tip. Many surgeons hydrate the incision via a cannula into the side walls of the incision only and not the roof, causing the tunnel to fishmouth and increasing the risk for 2-way leakage.
Initially, new surgeons find the injection technique somewhat challenging. There are specific points to optimizing the technique. To steady the globe, stabilize the eye as shown in Figure 1, A, of Nithyanandarajah et al.’s article1 or, alternatively, one can use an epee-like thrust to bury the entire bevel of the needle without a stabilizing instrument. This is especially important when using the technique for closing the paracentesis, as one cannot hold the eye steady with an instrument in the main incision. If entry is difficult, examine the tip of the needle because some needles will develop a bent tip. Practicing the angle of approach in a dry lab with a Kitaro eye or a cadaveric cornea can be helpful. Beginning with a bevel-up technique helps with the surgeon’s view of the tip, ensuring the entire needle port is within the stroma.
Regarding the mechanism of action, Wang et al.2 reported on variations in the internal incision entry point on optical coherence tomography (OCT) imaging and suggest there is more to this effect than the anticipated few hours of edema induced by infusion alone. The OCT of my patients’ incisions 4 hours and 1, 7, and 14 days after surgery demonstrated posterior bowing of Descemet membrane and endothelium, with overlying edema for 14 days. Combined, these findings suggest that discontinuity of the endothelium and Descemet membrane induced by incision and subsequent posterior bulging will allow that area to develop and maintain stromal edema or iatrogenic hydrops. This would be expected to resolve when the endothelium grows across the Descemet break. Needle hydration may be better than cannula wound-face hydration, Wong pocket, and even sutures to prevent leakage, as the effect on Descemet discontinuity lasts longer than in any of the other options. Optical coherence tomography evaluation of incisions closed in this manner at 1 and 3 months could determine when the Descemet discontinuity is eliminated.
1. Nithyanandarajah G, Athanasiadis Y, Scollo P, Sharma B, Dorgham A, Sharma A. Hydration of the anterior stroma in phacoemulsification cataract surgery. J Cataract Refract Surg
2. Wang L, Dixit L, Weikert MP, Jenkins RB, Koch DD. Healing changes in clear corneal cataract incisions evaluated using Fourier-domain optical coherence tomography. J Cataract Refract Surg
Other Cited Material
A. Jay McDonald, MD. Personal communication, December 2007.