Intraoperative Peripheral Iridotomy for Endothelial Keratoplasty with a 22-Gauge Needle

To describe the approach and advantages of a 22-gauge (22G) needle for intraoperative peripheral iridotomy (PI) during endothelial keratoplasty.

A superior approach is utilized to make an inferior PI. Intracameral lidocaine 1% and acetylcholine chloride 1% are injected intracamerally via a superior 1.1mm paracentesis incision for pain control and miosis. The 22G needle is bent near the hub with the bevel facing down. It is inserted through the paracentesis and passes through the pupil. As the needle-tip advances under the inferior iris, it is lifted periodically to identify its position until it reaches the ideal point for the PI. Counter-pressure is applied to the limbus at the exit point. The needle-tip is angled up and pushed through the iris and limbus so that the needle-shaft creates a standardized, patent, circular iridotomy (approximately 0.7mm diameter and 0.4mm² area). We compared the time needed for PI creation using intraocular scissors versus a 22G needle by evaluating 10 surgical videos for each technique and statistically analyzing the timings using the Mann-Whitney U test and Bootstrapping.

The median time to produce a PI using a 22G needle was 19 seconds (IQR: 14 to 24), compared to 85.5 seconds (IQR: 57 to 258) when using intraocular scissors (p<0.001, difference: 66.5 seconds, 95% CI: 33.5 to 238 seconds).

A 22G needle offers a safe, affordable, and efficient method using a standardized size diameter to produce an inferior PI during endothelial keratoplasty. Additional studies would assist to identify an ideal needle size across global populations.