Fig. 4 |. Volumetric imaging with and without active tracking in a freestanding individual.

a, Sequential anterior segment 800 × 400 × 1,376 voxel volumes 1–8 (from left to right) without registration during transient suspension of axial tracking for t₁ < t < t₂ (grey) and lateral tracking for t₃ < t < t₄ (grey). Loss of either active-tracking dimension produced large disturbances in the raw data, compared with the fully tracked volumes 4 and 8. B, artefacts from blink. b, Axial shift required to register each volume from a, demonstrating increased axial motion artefact only for t₁ < t < t₂ (grey) when axial tracking was suspended. Mean shift from volumes 4–8 taken as background. c, Lateral shift required to register each volume from a, demonstrating increased lateral motion artefact only for t₃ < t < t₄ (grey) when lateral tracking was suspended. Mean shift from volumes 1–4 and 8 taken as background. d,e, Axial (d) and lateral (e) alignment error from pupil tracking that aligns approximately with b,c. The physical eye motion correlates with the registration shift during the two tracking suspension periods, revealing the motion-stabilization effect of active tracking. B, tracking loss during blink.