An optical injection system for use in conjunction with a microscope having a turret supporting an objective having an optical path is provided. The optical injection system includes a dichroic mirror disposed between the turret and the objective, along the optical path. A collimating lens is further provided having an optical path directed to intersect the dichroic mirror. A laser source is positioned to project a laser beam through the collimating lens and along the collimating lens optical path. The laser can be used in conjunction with the microscope for a number of microsurgery applications. A method for calculating and displaying the isothermal contours of the energy produced by a laser in a sample is also provided.