METHODS: Scanning electron microscopy was performed on P50 and P200 devices. Bench-top flow studies were performed to find the resistances of the devices. Devices were also incorporated into a perfused, ex vivo porcine sclera model to test and compare their control of pressure, with and without overlying scleral flaps, and with trabeculectomies.
RESULTS: The luminal dimensions of the P200 device were 206.4±3.3 and 204.5±0.9 μm at the subconjunctival space and anterior chamber ends, respectively. Those of the P50 device were 205.0±5.8 and 206.9±3.7 μm, respectively. There were no significant differences between the P200 and P50 devices (all P>0.05). The resistances of the P200 and P50 devices were 0.010±0.001 and 0.054±0.002 mm Hg/μL/min, respectively (P<0.05). Equilibrium pressures with overlying scleral flaps were 17.81±3.30 mm Hg for the P50, 17.31±4.24 mm Hg for the P200, and 16.28±6.67 mm Hg for trabeculectomies (P=0.850).
CONCLUSIONS: The luminal diameters of both devices are externally similar. The effective luminal diameter of the P50 is much larger than 50 μm. Both devices have low resistance values, making them unlikely to prevent hypotony on their own. They lead to similar equilibrium pressures as the trabeculectomy procedure when inserted under the scleral flap.
METHODS: This was a prospective non-randomized comparative study. Eyes with OAG and cataracts that were planned for either combined phacoemulsification and iStent implantation (iStent+CS) or phacoemulsification alone (CS) were recruited. The iStent inject (Model G2-M-IS) or iStent injectW (Model G2-W) trabecular micro-bypass stent (Glaukos Corporation, San Clemente, CA, USA) was implanted in the iStent+CS group. WDT was performed before and 3 months after surgery. WDT-IOP parameters including peak IOP, IOP fluctuation, and area under the curve (AUC) were compared between the two groups.
RESULTS: There were 20 eyes in the iStent+CS group and 16 eyes in the CS group. Both groups had similar pre-operative baseline IOP (15.6 ± 3.7 mm Hg vs. 15.8 ± 1.8 mm Hg in the iStent+CS and CS group, respectively, p = 0.883). The iStent+CS group experienced greater numerical reduction in peak IOP (2.6 ± 1.9 mm Hg vs. 1.9 ± 2.4 mm Hg; p = 0.355), IOP fluctuation (1.7 ± 2.2 mm Hg vs. 0.8 ± 2.5 mm Hg; p = 0.289), and AUC (54.8 ± 103.6 mm Hg × minute vs. 25.3 ± 79.0 mm Hg × minute; p = 0.355) than the CS group. There was more reduction in the number of anti-glaucoma medications in the iStent+CS group (1.4 ± 1.2) than the CS group (0.3 ± 0.9; p = 0.005).
CONCLUSION: Both combined phacoemulsification with iStent inject implantation and phacoemulsification alone reduced peak IOP, IOP fluctuation, and AUC, and none of these parameters showed statistically significant difference. Greater reduction in anti-glaucoma medications was seen in the combined group.