Abstract: A thermal compensation system for an optical lens that has a focus adjustment with visible focus distance numerals and a juxtaposed index line for identifying the focus distance. The index line is provided on an internal ring slidably mounted to rotate circumferentially with respect to a barrel portion of the optical lens that includes the focus distance numerals. An actuator mounted within the optical lens includes a wax motor that is responsive to temperature changes and mechanical lever that engages both the wax motor and the ring for causing circumferential movement of a ring in response to actuation movement of the wax motor as caused by temperature changes. Further, an adjustment cam is provided for adjusting the relative positions of the wax motor and lever for calibrating the temperature responsive movements of the ring bearing the index line.