Patient Positioning. Case reports suggest that patient positioning
resulting in direct pressure to eyes (e.g., from the use
of a headrest, sheet roll, or other device) may precede the
onset of CRAO or retinal ischemia in spine surgery patients
(Category B3 evidence).#13–16,25,33–42 One observational
study indicates that, in 19% of ION cases listed in the ASA
Visual Loss Registry, patient head position was maintained
with Mayfield pins with the eyes free of pressure9 (Category
B2 evidence).