Endothelial keratoplasty involves the supplantation of the endothelial cell layer along with Descemet’s membrane, which may or may not be supported with the layer of stroma in the donor graft.
An important consideration during an endothelial keratoplasty procedure is preventing and minimizing the loss of endothelial cells during the process of donor tissue preparation and also while inserting and repositioning the graft in the anterior chamber. Pupilloplasty is often performed to prevent the escape of air into the vitreous cavity, maintain the effective air tamponade in the anterior chamber and prevent posterior dislocation of the graft. The technical manipulation of graft unfolding is mainly performed in the central portion of the anterior chamber, where the knots of the pupilloplasty procedure are present. For this reason, Schoenberg and Price presented a pupilloplasty technique that is especially helpful in cases of endothelial keratoplasty, with the knot directed toward the posterior aspect of the iris tissue in order to prevent the mechanical rubbing of the knot with the donor graft.
The procedure of single-pass four-throw (SFT) pupilloplasty is well-described in peer-reviewed papers, and it was performed in cases that underwent pre-Descemet’s endothelial keratoplasty. The SFT technique does not comprise a true knot formation. It involves the formation of an approximation loop with no securing loop that leads to the formation of a helical structure, which is self-retaining and has a self-locking mechanism. A slight variation is adopted while performing SFT wherein only one paracentesis incision is framed for the introduction of a 26-gauge needle to dock the 10-0 needle that has the suture attached to it. This has potentially two advantages: First, it prevents the engagement and involvement of the 10-0 needle in the corneal bite, and second, with a decrease in paracentesis incision, the air tamponade can be more effective because the site of potential air leakage is decreased. The paracentesis incision should be chosen carefully depending on the site of the iris defect and the ease of maneuverability. Moreover, the procedure of loop withdrawal is also performed from the paracentesis side because only one paracentesis incision is framed.
The suture ends, when trimmed, are essentially parallel to the surface of the iris and do not protrude into the anterior chamber. Hence, the chances of the knot rubbing on the endothelial cells of the donor graft are negligible. Anterior segment OCT analysis was done with the images being taken at the level of the iris, which demonstrated an elevation of around 136 µm to 160 µm in the longitudinal meridian and 160 µm to 175 µm in the cross-sectional meridian from the adjoining iris plane. Thus, the SFT procedure has a role in cases undergoing endothelial keratoplasty with virtually no damage from the knot of the suture that potentially lies parallel to the iris tissue.
- 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: firstname.lastname@example.org; website: www.dragarwal.com.
- Priya Narang, MS, can be reached at Narang Eye Care & Laser Centre, Ahmedabad, India; email: email@example.com.
Disclosures: Agarwal and Narang report no relevant financial disclosures.