Unsigned surface positioning errors observed in 28 volumetric OCT images. Inter-observer variability is shown in blue, errors of the original graph search method with only hard constraints are shown in red [8], and errors of the proposed method are shown in green. For all four surfaces, the resulting errors are significantly smaller than the corresponding inter-observer variabilities (p < 0.001). Compared with the original graph search method, our method showed a significant improvement for surfaces 2, 3, and 4 (p < 0.05).