OpenCV implements the Lucas-Kanade sparse optical flow method via the cv2.calcOpticalFlowPyrLK() function. This method performs a least-squares fit on the motion of a 3x3 pixel neighborhood (9 points) around each target point, assuming small movement between consecutive frames to satisfy the brightness constancy constraint. The function accepts the previous frame, the next frame, and the tracking points from the previous frame, returning the updated points and a status vector indicating successful tracking.