A method of determining control parameters of a retinal treatment system comprising acquiring an image of a retina of a subject's eye using an imaging laser and an optical system of the retinal treatment system, presenting an image of the retina to a user of the retinal treatment system, receiving from the user location data of the retinal image that locates at least one treatment site of the retina, receiving from the user a required laser light pattern for use on the treatment site, using the location data to determine a location control parameter which causes the optical system to direct laser light from a treatment laser of the retinal treatment system to the treatment site, and using the required laser light pattern to determine a pattern control parameter which causes the treatment laser to produce a laser light pattern which passes through the optical system and results in the required laser light pattern at the treatment site.
