Repeat 15-psi blast exposure causes greater and faster axon degeneration and vision loss than a single 15- or 26-psi blast. (A–D) Representative brightfield micrographs of ipsilateral optic nerve cross-sections from sham (A), 2-week single 15-psi (B), 2-week single 26-psi (C), and 2-week repeat 15-psi blast (D). (E) Quantification of total axons in each group at 2 weeks after blast. (F) Quantification of degenerative axon profiles in each group at 2 weeks after blast. (G and H) Representative brightfield micrographs of ipsilateral optic nerve cross-sections from mice 4 weeks after a single 26-psi blast (G) or a repeat 15-psi blast (H). (I) Quantification of total axons at 4 weeks after blast. (J) Quantification of degenerative axon profiles at 4 weeks after blast. (K) Quantification of the VEP N1 wave amplitude in each group. (L) Quantification of the VEP N1 wave latency in each group. psi, pounds per square inch; VEP, visual evoked potential. Color image is available online.