A system for aligning head scans of a subject, the system comprising: non-transitory memory configured to store: a reference head scan of at least a portion of a head of the subject , and a second head scan of the head of the subject; and a hardware processor in communication with the non-transitory memory, the hardware processor programmed by executable instructions to: receive the reference head scan of the subject ; determine a reference center point of each eyeball of the subject and a reference inferred point in the reference head scan based on a plurality of reference candidate points of a sclera of the each eyeball of the subject in the reference head scan ; receive the second head scan of the subject ; determine a second center point of the each eyeball of the subject and a second inferred point in the second head scan based on a plurality of second candidate points of the sclera of the each eyeball of the subject in the second head scan ; determine an affine transformation from the second head scan to the reference head scan based on the second center point of the each eyeball of the subject and the second inferred point in the second head scan and corresponding points in the reference head scan ; and perform the affine transformation on at least the head of the subject in the second head scan to generate an affine-transformed head of the subject in the second head scan. non-transitory memory configured to store: a reference head scan of at least a portion of a head of the subject , and a second head scan of the head of the subject; and a reference head scan of at least a portion of a head of the subject , and a second head scan of the head of the subject; and a hardware processor in communication with the non-transitory memory, the hardware processor programmed by executable instructions to: receive the reference head scan of the subject ; determine a reference center point of each eyeball of the subject and a reference inferred point in the reference head scan based on a plurality of reference candidate points of a sclera of the each eyeball of the subject in the reference head scan ; receive the second head scan of the subject ; determine a second center point of the each eyeball of the subject and a second inferred point in the second head scan based on a plurality of second candidate points of the sclera of the each eyeball of the subject in the second head scan ; determine an affine transformation from the second head scan to the reference head scan based on the second center point of the each eyeball of the subject and the second inferred point in the second head scan and corresponding points in the reference head scan ; and perform the affine transformation on at least the head of the subject in the second head scan to generate an affine-transformed head of the subject in the second head scan. receive the reference head scan of the subject ; determine a reference center point of each eyeball of the subject and a reference inferred point in the reference head scan based on a plurality of reference candidate points of a sclera of the each eyeball of the subject in the reference head scan ; receive the second head scan of the subject ; determine a second center point of the each eyeball of the subject and a second inferred point in the second head scan based on a plurality of second candidate points of the sclera of the each eyeball of the subject in the second head scan ; determine an affine transformation from the second head scan to the reference head scan based on the second center point of the each eyeball of the subject and the second inferred point in the second head scan and corresponding points in the reference head scan ; and perform the affine transformation on at least the head of the subject in the second head scan to generate an affine-transformed head of the subject in the second head scan. <EOS>