Aim. To explore the impact of interference on the cognitive load of nursing work. Methods. This was a field observational study. ICU nurses wore a wearable eye tracker, Tobii Glasses 3 (sampling rate 100 Hz), for approximately 2 h during their shift. The nurses performed their daily tasks as usual. The nurses’ pupil diameter, working time using the nursing information system, and whether they were distracted while using the nursing information system were recorded. Paired T-tests were used to compare the pupil diameters of the 26 nurses when performing the nursing information system tasks with and without distractions. Results. The nurses were observed to complete work on the nursing information system for a total of 289 min, including 206 min with interference and 81 min without interference. Pupil diameters were significantly larger when nurses were interacting with nursing information systems with interference (3.22 ± 0.42 mm vs. 3.15 ± 0.43, P = 0.009). Conclusions. Our study highlights the significant impact of interference on the cognitive load of ICU nurses, as evidenced by changes in pupil diameter. These findings emphasize the importance of developing strategies to reduce interruptions and manage cognitive workload effectively in high-stress environments like the ICU.