AAOjournal posts microshunt study
- Ophthalmology Glaucoma published an in-vitro study showing intraluminal sutures can sharply change flow resistance inside SIBS microshunts used in glaucoma surgery. - In five microshunts, resistance rose from 1.74 without occlusion to 3.42 with 4 mm 10-0 nylon and 5.11 with 4 mm 9-0 nylon. - The findings arrive as surgeons test stented PreserFlo techniques to reduce postoperative hypotony in clinical practice. (clinicaltrials.gov)
Glaucoma damages the optic nerve when pressure inside the eye stays too high. A microshunt lowers that pressure by draining fluid through a tiny tube. (clinicaltrials.gov) (ophthalmologyglaucoma.org) The new Ophthalmology Glaucoma paper tested what happens when surgeons partially block that tube with a thread-like suture placed inside the lumen. The study was published online March 30, 2026. (pubmed.ncbi.nlm.nih.gov) (ophthalmologyglaucoma.org) Researchers led by William J. Herspiegel used five SIBS microshunts in a lab gravity-perfusion setup and ran four replicated five-minute trials for each condition. They tested 4 millimeter and 8 millimeter insert lengths, 9-0 and 10-0 diameters, and nylon versus Vicryl material. (pubmed.ncbi.nlm.nih.gov) Without any suture, outflow resistance measured 1.74 ± 0.06 millimeters of mercury per microliter per minute, almost identical to the 1.76 predicted by the Hagen-Poiseuille formula. A 4 millimeter 10-0 suture raised resistance to 3.42 for nylon and 3.55 for Vicryl. (pubmed.ncbi.nlm.nih.gov) An 8 millimeter 10-0 suture pushed resistance higher, to 4.66 for nylon and 5.08 for Vicryl. A 4 millimeter 9-0 suture raised resistance to 5.11 for nylon and 5.00 for Vicryl. (pubmed.ncbi.nlm.nih.gov) That matters because too little resistance can leave the eye draining too fast after surgery, causing hypotony, or abnormally low eye pressure. The paper says small changes in suture length, thickness, and material can materially change flow behavior. (pubmed.ncbi.nlm.nih.gov) (clinicaltrials.gov) The device family is already under scrutiny in clinical studies. A randomized trial reported that the MicroShunt had lower surgical success than trabeculectomy in primary open-angle glaucoma, while a separate long-term safety analysis compared complications between the two operations. (aaojournal.org) (ophthalmologyglaucoma.org) Other lab work points in the same direction. A 2025 study in Eye found that larger stents and polypropylene produced more resistance in the PreserFlo MicroShunt, with median resistance reaching 37.55 for 9-0 polypropylene. (nature.com) Clinical testing is now catching up. A prospective randomized study of a releasable intraluminal suture technique in the PreserFlo device was posted to ClinicalTrials.gov on April 15, 2026, with an estimated start date of May 1, 2026. (clinicaltrials.gov) The lab result does not show that one suture recipe improves patient outcomes. It shows that inside a 70-micron drainage channel, a millimeter-scale tweak can change pressure resistance by multiples, not margins. (pubmed.ncbi.nlm.nih.gov) (ophthalmologyglaucoma.org)
