Optic Nerve Sheath to Eyeball Diameter Ratio on Brain Computed Tomography and Mortality in Comatose Adult Post-Arrest Patients

Background: Prognostication after return of spontaneous circulation (ROSC) in comatose patients following out-of-hospital cardiac arrest (OHCA) remains challenging. This study aimed to evaluate the relationship between brain computed tomography (CT) derived optic nerve sheath diameter/eyeball transverse diameter (ONSD/ETD) measurements and mortality in this patient population.Methods: This retrospective, single-center observational study included adult comatose OHCA patients who achieved ROSC and underwent brain CT between January 2019 and January 2023. ONSD and ETD measurements were obtained from early post-arrest CT scans, and ONSD/ETD ratios were calculated. The primary outcome was 30-day mortality. Demographic, clinical, laboratory, and imaging variables were compared between mortality groups.Results: A total of 159 patients were included; 82 (51.6%) were male, and the median age was 76 years (IQR 67–84). Overall mortality was 80.5% (128/159), and patients in the mortality group were older than those in the non-mortality group (p=0.003). Median right and left ONSD values were 6.33 mm (5.91–6.98) and 6.37 mm (5.93–6.93), respectively, while median right and left ETD values were 2.25 cm (2.19–2.33) and 2.26 cm (2.20–2.33). The ONSD/ETD ratios in the mortality group were 0.28 (0.26–0.30) for both the right and left eyes. No significant differences were observed between mortality and non-mortality groups regarding ONSD, ETD, or ONSD/ETD measurements.Conclusions: In this study comatose patients after ROSC, early CT-derived ONSD and ONSD/ETD measurements did not differ between mortality groups. These findings suggest limited utility of early CT-based optic nerve metrics for mortality assessment in the immediate post–cardiac arrest period.