An enrollment template can be a collection of interest points such as vascular points (VPD) and corresponding features such as Enhanced Multi-Radii Local Binary Patterns (EMR-LBP), Pattern Histograms of Enhanced Multi-Radii Local Binary Patterns (PH-EMR-LBP), Pattern histograms of Enhanced Multi-Radii Center-Symmetric Local Binary Patterns (PH-EMR-CS-LBP), and Enhanced Multi-Radii Center-Symmetric Local Binary Patterns (EMR-CS-LBP). In some implementations, an enrollment template can be created only if the acquired image exceeds a certain threshold based on ratio of VPD points to that of size of segmented scleral region. More than one enrollments are possible for a single user. Enrollment templates can be updated to accommodate behavioral and/or environmental variations affecting the acquired scans. Updating the enrollment templates using verification can be based on quality of a candidate verification template, match score, and/or other image and exposure similarity measures.