An ophthalmic surgical system includes a robotic arm disposed above a patient's eye. A positioning camera is disposed on the robotic arm and positioned to visualize the patient's eye. A processor is electrically coupled to the positioning camera. The processor is configured to receive an indication of a position of the robotic arm relative to a fixed datum, determine a focal length between the positioning camera and the patient's eye, compare the focal length to the position of the robotic arm, and determine a patient eye level relative to the fixed datum.