The cross-ratio approach has recently attracted increasing attention in eye-gaze tracking due to its simplicity in setting up a tracking system. Its accuracy, however, is lower than that of the model-based approach, and substantial efforts have been devoted to improving its accuracy. Binocular fixation is essential for humans to have good depth perception, and this paper presents a technique leveraging this constraint. It is used in two ways: First, in estimating jointly the homography matrices for both eyes, and second, in estimating the eye gaze itself. Experimental results with both synthetic and real data show that the proposed approach produces significantly better results than using a single eye and also better than averaging the independent results from the two eyes.