Is PKP a Timeless Procedure?

Suggestions on choosing and improving outcomes of penetrating keratoplasty. Cheryl Guttman Krader reports. Even in the current era of lamellar corneal transplantation, there remain timeless indications for performing penetrating keratoplasty (PKP), notes Professor Berthold Seitz MD. Addressing the question “Should we still do PKP?” at a recent conference, Prof Seitz answered, “Of course.” He described situations where a full-thickness transplant is indicated and reviewed technical details for preventing complications and optimising success after PKP. “The principal indications for PKP include optical grafts in eyes at normal risk for rejection but especially in high risk optical grafts and therapeutic grafts,” Prof Seitz said. His list of indications for PKP included post-PKP eyes with high astigmatism (with and without endothelial decompensation), those with advanced keratoconus, aphakia, and eyes with an unstable cornea (e.g., post-radial keratotomy, descemetocele, or perforated ulcer), among others. In addition, PKP is indicated in eyes with all types of infectious keratitis. OPTIMISING OUTCOMES Although eye banks apply established criteria when accepting corneal tissue for grafting, the requirements did not consider curvature abnormalities present in eyes with keratoconus or a history of laser vision correction. Therefore, Prof Seitz and colleagues introduced sterile donor tomography using anterior segment OCT as a screening tool for detecting corneal tissues with refractive anomalies. “Using sterile donor tomography in the eye bank to measure the front and back radii of curvature and corneal thickness, we can optimise donor selection and prevent refractive surprises after PKP. Donor corneas that should not be used for PKP or deep anterior lamellar keratoplasty because of curvature issues may still be suitable for Descemet membrane endothelial keratoplasty or Descemet stripping automated endothelial keratoplasty,” he explained. Prof Seitz said that with safety in mind, PKP is typically performed under general anaesthesia with controlled arterial hypotension and maximal relaxation. However, he cautioned against using mivacurium as the muscle relaxant because it is associated with an increased risk of vis-a-tergo. He emphasised the importance of horizontal positioning of the head and limbal plane to avoid decentration, vertical tilt, and horizontal torsion that could lead to high and/or irregular astigmatism. rof Seitz also discussed the use of excimer laser trephination and metal masks with “orientation teeth”, which he said reduces astigmatism, improves surface regularity, and results in better visual acuity. In addition, this technique has practical advantages for the surgeon that includes enabling the exact positioning of the second cardinal suture. “Recently we introduced the use of the Amaris® 1050RS excimer laser (Schwind) for trephination with a pseudoring profile that improves the results,” he added. Other tips mentioned included making an open-sky iridotomy at 12 o’clock peripherally to prevent the so-called Urrets-Zavalia syndrome and using the Homburg cross-stitch marker (Geuder) to support precise localisation of double-running cross-stitch sutures. “The double-running cross-stitch suture is preferred as long as Bowman’s layer is intact since it results in higher topographic regularity, earlier visual rehabilitation, and lessens the risk of suture loosening and consequently the rate of resuturing,” he said. “Using the Homburg cross-stitch marker for placing the double-running sutures allows even inexperienced surgeons to achieve good results.” Prof Seitz presented his findings during the ESCRS Virtual Winter Meeting 2022. Berthold Seitz MD is Professor and Director of the department of ophthalmology at Saarland University Medical Centre, Homburg/Saar, Germany. berthold.seitz@uks.eu