Abstract Background There are no data on usefulness of optic nerve sheath diameter (ONSD) as a marker of patient’s fluid status in preeclampsia. The objective was to examine potential correlation between ONSD and lung ultrasound estimates of extravascular lung water in severe preeclampsia. Patients and methods Thirty patients with severe preeclampsia were included. Optic and lung ultrasound were performed within 24 hours from delivery. ONSD was measured 3 mm behind the globe. Lung ultrasound Echo Comet Score (ECS) was obtained summing B-lines (“comet tails”) in parasternal intercostal spaces bilaterally. Pearson’s correlation analysis was used to assess the relationship between ONSD and ECS (p < 0.05 significant). Results Median ONSD was 5.7 mm (range 3.8–7.5 mm). Median ECS value was 19 (range 0-24). Statistically significant correlation was found between ONSD and ECS (r² = 0.464; p < 0.001). Conclusions Significant correlation between ONSD and ECS suggests optic ultrasound could be used for assessing fluid status and guiding peripartum fluid therapy in patients with severe preeclampsia.