⚡ Key Takeaways
- A 10-0 Nylon suture threaded through the MicroShunt lumen acts as a flow restrictor
- This "ripcord" technique prevents early postoperative hypotony
- The stent allows some flow (it doesn't completely occlude the lumen)
- When the bleb is ready, the ripcord is removed at the slit lamp for full flow
- This gives you postoperative IOP control similar to releasable sutures in trabeculectomy
Watch the Full Video
The Problem: Early Hypotony
The Preserflo MicroShunt is an effective glaucoma drainage device, but its 70-micron lumen can allow too much flow in the early postoperative period — before the bleb tissue has developed enough resistance. This leads to hypotony, which can cause choroidal effusions, maculopathy, and patient discomfort.
The Solution: Nylon Ripcord
By threading a 10-0 Nylon suture through the MicroShunt lumen before implantation, you partially occlude the tube. This reduces initial flow while still allowing some aqueous drainage. The result: a gentler pressure reduction that gives the bleb tissue time to mature.
Surgical Technique
- Prepare the 10-0 Nylon suture — cut it to appropriate length
- Thread it through the MicroShunt lumen from one end to the other
- Leave one end accessible for later removal at the slit lamp
- Implant the MicroShunt as usual with the stent in place
- Ensure the Nylon end is tucked under the conjunctiva but retrievable
Postoperative Management
In the days and weeks after surgery, monitor the IOP and bleb. The stent restricts flow enough to prevent severe hypotony while still allowing a bleb to form. When you're satisfied with bleb development and wound healing, remove the ripcord at the slit lamp for full flow.
Frequently Asked Questions
Does the ripcord completely block flow?
No. The 10-0 Nylon suture doesn't perfectly fill the 70-micron lumen. Some aqueous still passes around it, which is desirable — you want controlled, reduced flow, not complete obstruction.
When is the ripcord typically removed?
Usually 2-6 weeks postoperatively, depending on IOP, bleb morphology, and wound healing. There's no fixed timeline — it's a clinical decision.
Can this technique be used with other tube shunts?
The ripcord concept is specific to the Preserflo MicroShunt's geometry. Other tube shunts (Ahmed, Baerveldt) use different methods for flow restriction, such as ligature sutures or the valve mechanism itself.
Learn more about the Preserflo MicroShunt
Watch the companion video on how to remove the ripcord at the slit lamp, or explore the Clinical Skills in Glaucoma course.