Intraocular Pressure Fluctuation as Assessed by Water Drinking Test following iStent Inject Implantation in Open-Angle Glaucoma Patients

Introduction: This study investigated the intraocular pressure (IOP) fluctuation as assessed by the water drinking test (WDT) in open-angle glaucoma (OAG) patients after combined cataract surgery with iStent implantation.

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.