Post-Operative Intraocular Pressure (Iop) Titration Using A New Laser-Adjustable Aqueous Shunt

Evaluate the ability to lower and raise IOP post-operatively by opening and closing the nitinol valves of a laser-adjustable sub-conjunctival aqueous shunt with modifiable postoperative outflow resistance using a green laser.

This ongoing, single-arm, multi-center feasibility clinical trial (NCT05885022) was conducted by glaucoma-trained physicians at four private clinics in Mexico, Panama, and India. A total of 31 patients with open-angle glaucoma were unilaterally implanted with the Calibreye System (Myra Vision, Campbell, CA) shunt with mitomycin C.

The shunt is designed to drain aqueous humor to the equatorial subconjunctival space via three microfluidic channels.  Two of the channels are controlled by nitinol valves that can be repeatedly opened or closed using a slit lamp mounted green laser.  After implantation, the investigators adjusted valves across 4 possible device resistance settings by opening and closing the valves with the objective of lowering and raising IOP, respectively.  IOP was assessed prior to and at least 30 minutes after laser titration and during subsequent follow-up visits.

Preoperative IOP was 22.7 ± 4.5 mmHg (mean ± SD) on 3.2 ± 1.2 medications with a visual field mean deviation of -19.0 ± 10.3 dB. A total of 70 laser titration procedures were performed in the first 6 months of follow up with the objective of modulating IOP. Of these, 64 procedures (ranging Day 1-181) were to open valves, which resulted in an overall mean IOP change of -3.1 mmHg (mean IOP pre-titration 11.8 ± 2.4 mmHg and post-titration 8.7 ± 1.9 mmHg).  The remaining 6 procedures (ranging Day 1-33) were performed to close valves, which resulted in an overall mean IOP increase of 2.2 mmHg (mean IOP pre-titration 5.2 ± 2.6 mmHg and post-titration 7.3 ± 3.0 mmHg).  No adverse events related to the laser titration procedure were reported.

By opening and closing valves using an in-office laser, the titratable shunt allowed postoperative titration of the IOP (increase and decrease) in the first 6 months post-implantation. This approach potentially offers the ability to reversibly modulate postoperative IOP and thus minimize vision threatening complications.