A simple bedside vision test may help predict recovery of consciousness in patients with severe brain injuries, according to new research presented at the 2026 European Academy of Neurology (EAN) Congress.
The study found that a previously overlooked phase of the pupillary response to light, known as the late lights-out response (LOR), predicted improvement in consciousness seven days later in acute brain injury patients. In contrast, standard pupillary measurements already widely used in intensive care units (ICUs), such as neurological pupillary index (NPi) and pupillary light reflex (PLR) latency, did not predict subsequent recovery of consciousness.
Predicting whether a patient will regain consciousness after severe brain injury remains one of the biggest challenges in intensive care. Automated pupillometry is already widely used in the ICU to assess brain function, but existing measurements primarily capture the pupil’s immediate response to light, with limited insight into long-term recovery.
Researchers from Copenhagen University Hospital Rigshospitalet and the Technical University of Denmark investigated whether the later stages of the pupillary reaction, which occur after the eye reacts to light, could provide further insight into the chances of recovery in patients with acute unconsciousness. The study involved 250 patients who suffered from disturbances of consciousness after traumatic and non-traumatic brain injury and 30 age- and gender-matched healthy controls. Patients underwent daily automated pupillary measurements and neurological evaluations for up to 20 days in the ICU.
This study found that slower LOR latencies independently predicted improvement in consciousness 7 days later, even after accounting for baseline neurological status, time since injury, sedation and injury type. Of note, this measurement was not associated with same-day patient reactivity levels, suggesting that it may reveal potential for recovery that was not apparent with routine bedside assessment.
Current pupillary function tests show how the brain is responding in the moment, but a slow lights-out response may provide clues about the brain’s potential for recovery. This could help us better understand which patients are likely to improve in the coming days. ”
Dr. Poul Laigaard, first author, Copenhagen University Hospital Rigshospitalet
The relationship was strongest in unsedated patients and in patients with anoxic-ischemic brain injury, a condition in which the brain lacks oxygen and blood flow. However, the researchers cautioned that the findings in these subgroups are exploratory and need to be confirmed in larger studies.
Professor Daniel Conziella, senior author of the study, added: “We believe this is an important observation that deserves further study. Larger multicenter studies are needed to determine whether this approach can be used routinely for bedside monitoring and prognosis.”
If validated in future studies, this approach could be relatively easy to implement, Dr. Rygaard explained, since the necessary technology is already available in many ICUs.
“Light-off response is measured using a hand-held automatic pupillometer in much the same way as current pupillary measurements. The entire assessment takes only 13 seconds per eye, making it a fast and practical bedside tool that could potentially be integrated into routine ICU care.”
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2026 European Academy of Neurology (EAN) Congress
