We propose 3D Multi-Texture Active Appearance Model (3D MT-AAM) where the skin and the eyeball are considered as two decorrelated objects contrary to classical AAM where the eye region is a continuous part of the face mesh. The iris is modeled as a sphere and rotates under the eye hole permitting the synthesis of new gaze directions. We compare the model with previous work that models the iris as a simple 2D texture and with a classical method and we obtain better results. In addition we propose a method for back-projecting the search result of our model from the model frame to the real image frame using barycentric coordinates. On the other hand, we explore different optimizations namely: Gradient descent (GD), Simplex, and Genetic Algorithm (GA) to optimize our model and we compare the performance of the system. We obtain the best performance using GA. However with Simplex we improve the computation time, with a slightly lower performance.