System and method for generating patterns P of aiming and treatment light on target eye tissue (e.g. the retina) of a patient's eye. The system includes light sources for treatment and aiming light, a scanner for generating patterns of spots of the generated light, a controller, and a graphic user interface that allows the user to select one of several possible spot patterns, adjust the spot density and/or spot size, and apply patterns with fixed or varied density. The patterns can be formed of interlaced sub-patterns and/or scanned without adjacent spots being consecutively formed to reduce localized heating. Partially or fully enclosed exclusion zones within the patterns protect sensitive target tissue from exposure to the light.