Intraoperative primary partial occlusion of the PreserFlo MicroShunt to prevent initial postoperative hypotony

Abstract

Purpose The aim of the underlying study was to present a new surgical method in PreserFlo MicroShunt surgery for glaucoma. A removable polyamide suture was placed into the lumen of the MicroShunt during implantation to prevent early postoperative hypotony. Methods Thirty-one patients undergoing stand-alone glaucoma surgery with implantation of a PreserFlo MicroShunt and an intraluminal occlusion were retrospectively reviewed and compared to a control group without occlusion. Inclusion criteria were diagnosis of primary open-angle glaucoma or secondary open-angle glaucoma due to pseudoexfoliation or pigment dispersion. Patients with a history of filtrating glaucoma surgery were excluded. Results IOP decreased from 26.9 ± 6.6 to 18.0 ± 9.5 mmHg at the first postoperative day after PreserFlo MicroShunt implantation. Postoperative removal of the occluding suture resulted in a mean IOP reduction in 11.1 ± 7.6 mmHg. Mean visual acuity was 0.43 ± 0.24 logMAR during the first postoperative examination. The interval with the occluding intraluminal suture in place varied from days to 2–3 weeks. Patients were followed up to 1 year. Conclusion Implantation of a PreserFlo MicroShunt combined with an intraluminal suture prevented postoperative hypotony in all patients. Mean postoperative pressure was reduced despite the occluding suture in place.

Exploring the Pressure Characteristics of the PRESERFLO MicroShunt in In Vitro Studies and Effects of Sclera on Device Performance

“…Reduced flow rates could also lead to decreased tube resistance and subsequent hypotony. Previous measures, such as placing removable polyamide sutures inside the PRESERFLO lumen, have effectively reduced the incidence of post-surgical hypotony [16]. The mechanisms underlying hypotony through reduced inflow and an increase in tube resistance by narrowing the lumen are well-explained by the equations discussed in this study.…”

“…The pressure at the proximal end (P 1 ) should represent the IOP of a human eye implanted with a PRESERFLO device. Unlike our experimental setup, when the PRESERFLO device is implanted in a human patient's eye, the distal end of the PRESERFLO is not free [16,17], and the resistance attributed to Tenon/subconjunctival tissues comes into play. Consequently, after surgical implantation of the PRESERFLO device, the IOP is expected to be higher than the peak pressure observed in the sclera 30 • condition in our study.…”

“…These clinical findings align with expectations, as the reported post-surgical IOP values were higher than the peak pressures observed in our study. One common early complication following PRESERFLO implantation is hypotony, defined as an IOP below 6 mmHg [16,20,21]. Hypotony can occur if there is an excessive flow of aqueous humor through the gap between the tube and the sclera, especially if the scleral tunnel width is too wide.…”

Minimally Invasive Glaucoma Surgery: Latest Developments and Future Challenges

“…156 Durr et al 157 looked at the success rate of PRE-SERFLO in eyes that had previously undergone a subconjunctival filtering surgery; they reported a complete success rate of 61% after 12 months, which was similarly observed by Schlenker et al 158 Hypotony was found in 63% during the early postoperative period, 159 with 11% having choroidal detachments. The intraoperative primary partial shunt occlusion with an 8.0 polyamide suture was described by Lüke et al 160 and may prevent postoperative hypotony. Despite PRESERFLO's meticulous design to esnsure safety, Saeed et al 161 showed that transient postoperative complications (hypotony, bleb fibrosis, hyphema, keratitis, and choroidal effusion) could be as much as 47%.…”