Single-pass four-throw pupilloplasty is a timber hitch type of knot that is self-retaining and self-locking. The technique comprises a single pass with four throws taken around the loop that is withdrawn from the anterior chamber.
So, the question now is: “How many sutures does it take to unravel?” The question has been answered by Brian Kim, MD, from Georgia, who precisely describes the experimental version of SFT knot mechanics in this video.
The developers of the technique (Priya Narang and Amar Agarwal) observed a similar thing in vivo that helped derive the terminology of single pass and four throws as four throws were found to be optimal to prevent the loop from unraveling. The video by Kim helps to understand the clinical situation in a better way.