A system for cataract surgery on an eye of a patient, comprising: a laser assembly for generating a pulsed laser treatment beam; an imaging system configured for imaging an ocular tissue of the patient, the ocular tissue comprising corneal tissue; an optical scanning system configured for positioning the focal zone of the treatment beam to targeted locations of the ocular tissue, the targeting locations including a location in the corneal tissue; and a computer control system operatively coupled to the laser assembly, the imaging system, and the optical scanning system, characterised in that the computer control system is programmed to: a) generate a simulated initial treatment scan and calculating an initial indication of iris exposure level corresponding to the initial treatment scan; b) determine whether the initial indication of iris exposure level satisfies a predetermined safe exposure condition; c) generate a simulated revised treatment scan comprising one or more treatment scan modifying elements when the initial indication of exposure level fails to satisfy the predetermined safe exposure condition, wherein the one or more treatment scan modifying elements cause a calculated revised indication of iris exposure level corresponding to the revised treatment scan to satisfy the predetermined safe exposure condition; and d) operate the optical scanning system and laser assembly to direct a treatment beam in a pattern corresponding to the revised treatment scan so as to create a corneal incision. a laser assembly for generating a pulsed laser treatment beam; an imaging system configured for imaging an ocular tissue of the patient, the ocular tissue comprising corneal tissue; an optical scanning system configured for positioning the focal zone of the treatment beam to targeted locations of the ocular tissue, the targeting locations including a location in the corneal tissue; and a computer control system operatively coupled to the laser assembly, the imaging system, and the optical scanning system, characterised in that the computer control system is programmed to: a) generate a simulated initial treatment scan and calculating an initial indication of iris exposure level corresponding to the initial treatment scan; b) determine whether the initial indication of iris exposure level satisfies a predetermined safe exposure condition; c) generate a simulated revised treatment scan comprising one or more treatment scan modifying elements when the initial indication of exposure level fails to satisfy the predetermined safe exposure condition, wherein the one or more treatment scan modifying elements cause a calculated revised indication of iris exposure level corresponding to the revised treatment scan to satisfy the predetermined safe exposure condition; and d) operate the optical scanning system and laser assembly to direct a treatment beam in a pattern corresponding to the revised treatment scan so as to create a corneal incision. a) generate a simulated initial treatment scan and calculating an initial indication of iris exposure level corresponding to the initial treatment scan; b) determine whether the initial indication of iris exposure level satisfies a predetermined safe exposure condition; c) generate a simulated revised treatment scan comprising one or more treatment scan modifying elements when the initial indication of exposure level fails to satisfy the predetermined safe exposure condition, wherein the one or more treatment scan modifying elements cause a calculated revised indication of iris exposure level corresponding to the revised treatment scan to satisfy the predetermined safe exposure condition; and d) operate the optical scanning system and laser assembly to direct a treatment beam in a pattern corresponding to the revised treatment scan so as to create a corneal incision.