Does Further Lowering Intraoperative Intraocular Pressure Reduce Surgical Invasiveness in Active-Fluidics Eight-Chop...

Background: Active-fluidics phacoemulsification can maintain anterior chamber stability at lower intraoperative intraocular pressure (IOP) levels. However, whether reducing IOP alone-without additional stabilizing technologies such as the Active Sentry handpiece-can decrease surgical invasiveness during Eight-Chop phacoemulsification remains unclear. Methods: In this prospective fellow-eye comparative study, 56 non-diabetic patients (112 eyes) underwent Eight-Chop technique phacoemulsification using the Centurion Vision System with active fluidics. One eye was randomly assigned to a standard-IOP setting (55 mmHg; high-IOP group) and the fellow eye to a reduced-IOP setting (28 mmHg; low-IOP group). Intraoperative parameters-including operative time, phaco time, aspiration time, cumulative dissipated energy (CDE), and irrigation volume-were recorded. Postoperative outcomes included aqueous flare (laser flare photometry), corneal endothelial cell density (CECD) and CECD loss, corneal morphology (central corneal thickness [CCT], coefficient of variation [CV], percentage of hexagonal cells [PHC]), and IOP. Linear mixed-effects models with patient ID as a random effect were used for all paired-eye comparisons. Results: Lowering the intraoperative IOP did not reduce surgical invasiveness. Phaco time was significantly longer in the low-IOP group (16.2 ± 5.22 s vs. 13.9 ± 4.40 s; p = 0.001), and aspiration time was also longer (75.0 ± 18.3 s vs. 69.0 ± 17.9 s; p = 0.033). No significant differences were found in operative time (5.08 ± 1.10 min vs. 4.82 ± 1.13 min; p = 0.082), CDE (5.93 ± 1.87 vs. 5.56 ± 1.90; p = 0.099), or irrigation volume (26.6 ± 7.71 mL vs. 25.2 ± 7.35 mL; p = 0.214). Postoperative outcomes were similarly comparable. Aqueous flare showed no significant differences at any time point (e.g., day 1: 14.8 ± 5.10 vs. 14.5 ± 4.76 ph/ms; p = 0.655). Mean CECD loss remained small in both groups and did not differ significantly (7 weeks: -0.82 ± 1.05% vs. -0.98 ± 1.16%, p = 0.460; 19 weeks: -0.93 ± 1.38% vs. -1.28 ± 1.69%, p = 0.239). Corneal morphological parameters (CCT, CV, PHC) and postoperative IOP also showed no significant differences between settings. Conclusions: In this fellow-eye comparative study, lowering intraoperative intraocular pressure from conventional to near-physiologic levels under active-fluidics control did not reduce surgical invasiveness during Eight-chop phacoemulsification. No additional benefits were observed in terms of endothelial cell preservation, postoperative inflammation, or overall surgical performance. These findings indicate that, when chamber stability is already ensured by a low-invasive fragmentation strategy, further reduction in intraoperative IOP alone does not confer measurable short-term clinical advantages.