The iris region matching would be the core of the visible-spectrum gaze tracker. The design challenge is much more difficult than the one of the traditional infra-ray gaze tracker due to the imperfection of the eye images. In practical application environments, the iris regions on the eye images may be influenced by the reflection light, and the matching process is also affected by the eyelids and wrinkles near the eyes. In this paper, we further improve the fitness function used for iris region matching. The experimental results show that the new one can effectively prevent the matching results from being dominated by the wrong textures near the eyes.