Purpose: To evaluate the incidence of optic cracks and/or fractures during foldable acrylic intraocular lens (IOL) implantation via the manual Monarch delivery system with the cartridge and to determine factors that help to avoid such complications.Methods: Small-incision phacoemulsification surgery was performed in 702 eyes with visually significant cataract formation. A foldable acrylic soft IOL (AcrySofâMA60BM/MA30BA, Alcon, Fort Worth, TX, USA) or a single-piece acrylic soft IOL (Acriva BBâ, VSY Biotechnology, Amsterdam, The Netherlands) was inserted in all eyes using a cartridge and viscoelastic agents (sodium hyaluronate, Healon®, Advanced Medical Optics, Santa Ana, CA, USA).Results: Postoperative central, paracentral, or peripheral optic cracks or fractures were encountered in a total of six of 702 eyes (0.85%). Four of six lenses (0.57%) had optic cracks within the IOL substance, whereas two of 702 cases (0.28%) had full-thickness IOL fractures in the substance in multiple locations. Three of the four lenses with optic cracks were noted to be handled by tying forceps during the cartridge insertion, and one of them was the complication of holding forceps. Two IOLs with full-thickness optic fractures were encountered during the insertion of the IOLs in the capsular bag as a result of direct trauma to the lens optic by the plunger of the injector system overriding the lens optic during cartridge passage. None of the patients suffered from glare or other visual disturbances postoperatively, and, therefore, none of the six eyes required lens replacement.Conclusion: The unintentional extensive pressure effect of the forceps during the holding process of the IOL or the direct trauma to the lens optic by the plunger of injector systems may cause optic cracks or fractures. Physicians should continue to monitor the eyes postoperatively regularly and must determine the benefits and risks to be derived from lens replacement, if such patients complain of significant glare, image degradation, and visual disturbances. We recommend the use of preloaded lenses, which have their own delivery systems and cartridges, to minimize the risk of such complications.