To assess the impact on incision size of IOL implantation using a new motorized intraocular lens (IOL) injector versus a standard manual injector.Cataract Treatment Centre, Sunderland Eye Infirmary, Sunderland, United Kingdom.Comparative case series.All patients received an Acrysof SN60WF IOL implanted using a D cartridge and an Autosert motorized injector at fast speed, an Autosert motorized injector at slow speed, or a manual Monarch injector. Each group had a range of preimplantation incision sizes (1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm). Incision gauges were used to measure the incision width before and immediately after IOL implantation.The study recruited 256 patients. All incisions that were 1.8 mm at the commencement of surgery increased in size by the end of irrigation/aspiration. The motorized injector used with a fast speed (4.4 mm/sec) caused significantly less incision enlargement than the manual injector for all preimplantation incision sizes tested (P<.02). For 4 of the 5 preimplantation incision size subgroups, the motorized injector used at slow speed (1.5 mm/sec) produced less incision stretch than the manual injector, although the difference did not reach statistical significance.The motorized injector was easy to use, and its use with an injection speed of 4.4 mm/sec caused significantly less incision enlargement than the manual injector during IOL implantation.