Phacoemulsification surgery is the standard treatment for cataract. However, excessive ultrasound (US) energy may cause injury to the corneal endothelium and other ocular tissues. Recently, a new prechop technique assisted with the reverse chopper is showed to be more efficient and safe, by splitting the nuclei in situ without using any US energy. However, it is verified only in treating some kinds of complex cataracts such as grade IV hard nuclei cataract, small-pupil cataract, and ultra-high myopia cataract. Since grade III nuclei cataract is the most common type of cataract, it is necessary to evaluate the efficacy and safety of prechop technique with reverse chopper in routine cataract surgery.This prospective, two-parallel, randomized controlled trial was conducted in Beijing Tongren Hospital from January 2022 to September 2022. A total of 89 cataract patients (89 eyes) were enrolled and then randomly assigned to either the reverse chopper-assisted prechop group (n=45) or the phaco-chop group (n=44). The patients were followed for 3 months postoperatively. The best-corrected visual acuity (BCVA), cumulative dissipated energy (CDE), corneal endothelial cell loss (ECL), and degree of corneal edema were evaluated and compared between these 2 groups. Data were analyzed using SPSS 23.0 and GraphPad Prism 8.0.The CDE of the reverse chopper-assisted prechop group was significantly less than that of the phaco-chop group (P=0.011). Compared with the phaco-chop group, the corneal edema in the reverse chopper-assisted prechop group was milder (P=0.026) and the BCVA was better (P=0.0012) at 1 day after surgery. No significant difference was found in the count or rate of corneal ECL between the 2 groups at 1 month after surgery (corneal ECL count: P=0.090; corneal ECL rate: P=0.053). The BCVA of the 2 groups at 1 week, 1 month, and 3 months after surgery was equivalent (P=0.052, 0.26, and 0.41, respectively).The prechop technique assisted with the reverse chopper in treating cataract with grade III nuclei enables less phaco energy consumption, milder ocular structural damage, and faster recovery of vision, compared with traditional phaco-chop technique.2023 Annals of Translational Medicine. All rights reserved.