Efficacy and safety of clamp-and-chop phacoemulsification as a standardized universal technique: A nucleus density-stratified prospective randomized controlled trial

Objective
This stratified randomized controlled trial (RCT) aimed to compare the clinical value of clamp-and-chop phacoemulsification versus conventional in-situ phacoemulsification for age-related cataract (ARC) across different lens nucleus density grades. Intraoperative energy parameters, corneal endothelial injury, and postoperative imaging and recovery outcomes were objectively quantified to validate the efficacy and safety of clamp-and-chop as a universal standardized cataract surgical technique, and to provide evidence-based support for its widespread clinical adoption.

Methods
This prospective study enrolled 140 patients (140 eyes) with ARC treated at our hospital between January 2025 and January 2026. Patients were stratified into two subgroups by lens nucleus density according to the Lens Opacities Classification System III (LOCS III): mild-to-moderate nucleus and hard nucleus. Within each stratum, patients were randomized 1:1 to the study group or control group (70 eyes per group). All surgeries were performed by a single senior cataract surgeon with identical device parameters. The study group received clamp-and-chop phacoemulsification, in which the nucleus was mechanically split via instrument counter-force followed by low-energy ultrasound aspiration; the control group received conventional in-situ phacoemulsification, including groove sculpting, stop-and-chop, and counter-chop techniques. Intraoperative cumulative dissipated energy (CDE) and effective phaco time (EPT) were recorded. Non-contact specular microscopy and anterior segment optical coherence tomography (AS-OCT) were used to measure corneal endothelial cell (CEC) loss rate and central corneal thickness (CCT) at baseline, 1 week, 1 month, and 3 months postoperatively. Best-corrected visual acuity (BCVA), surgical complications, and postoperative visual analog scale (VAS) pain scores were also documented at all follow-up time points.

Results
Intraoperative CDE, EPT, and irrigating solution volume were significantly lower in the study group than in the control group (all P < 0.05). At 1 and 3 months postoperatively, the study group had significantly lower CEC loss rates and smaller CCT increases compared with the control group; this advantage was more pronounced in the hard nucleus subgroup. BCVA improved from baseline in both groups at all follow-up points, with more stable visual recovery observed in the study group. No severe intraoperative complications (including posterior capsular rupture or zonular dialysis) occurred in the study group; the overall complication rate and postoperative VAS pain scores were also lower in the study group relative to controls.

Conclusions
Compared with conventional in-situ chopping techniques, clamp-and-chop phacoemulsification relies on mechanical force for nucleus fragmentation, which effectively reduces intraoperative ultrasound energy consumption and mitigates corneal endothelial injury, demonstrating an excellent endothelial protective effect. This technique is applicable to cataracts of all nucleus densities, with particularly prominent clinical benefits in hard nucleus cases, along with high intraoperative safety and rapid postoperative recovery. With a standardized, consistent surgical workflow and shallow learning curve, clamp-and-chop phacoemulsification can be adopted as a universal standardized technique for both routine and complex cataract surgery, with high value for widespread clinical promotion.