13-second eye test predicts consciousness recovery after severe brain injury

A novel bedside eye assessment could significantly improve doctors’ ability to forecast recovery in patients with severe brain injuries

New research presented at the European Academy of Neurology (EAN) Congress 2026 demonstrates that analysing a specific, previously overlooked phase of the pupil’s reaction to light can predict whether a patient will regain consciousness seven days later.

The study was conducted by researchers from Copenhagen University Hospital, Rigshospitalet, and the Technical University of Denmark.

Reimaging the pupil’s reflex

Forecasting consciousness recovery is a significant clinical challenge in intensive care units (ICUs). While automated pupillometry—using a handheld digital device to measure how the pupil reacts to light—is standard practice in modern ICUs, existing metrics focus entirely on immediate reflexes.

Currently utilised metrics include:

• The Neurological Pupil Index (NPi): A composite score measuring overall pupillary reactivity.
• Pupillary Light Reflex (PLR) Latency: The speed at which the pupil constricts when a light is shone into it.

The study found that while standard NPi and PLR data tell doctors how the brain is functioning in the moment, they do not accurately predict future improvement. Instead, the breakthrough predictive indicator lies in the late light-off response (LOR)—the precise timeline of the pupil’s behavior and dilation after the stimulus light is turned off.

Unlocking unseen recovery potential

The clinical trial tracked 250 patients suffering from impaired consciousness caused by both traumatic and non-traumatic brain injuries, comparing them against 30 healthy controls. ICU patients received daily automated pupillometry tests alongside standard neurological assessments for up to 20 days.

The analysis yielded two vital insights:

• Independent prediction: Late LOR latency independently predicted visible improvements in a patient’s consciousness one week later. This holds true even after mathematically adjusting for baseline neurological status, time elapsed since the injury, sedation levels, and the specific type of injury.
• Hidden trajectory: A patient’s late LOR latency did not correlate with their actual physical responsiveness on the day of the test. This suggests the reflex uncovers latent biological recovery potential that standard physical bedside examinations miss entirely.

The statistical relationship appeared strongest in patients who were not taking sedative medications and those suffering from anoxic–ischaemic brain injuries (where the brain was starved of oxygen and blood flow). However, researchers note these sub-group findings remain exploratory and require broader validation.

Seamless integration into ICU care

Because the diagnostic technology is already integrated into the workflow of many modern ICUs, transitioning this discovery into a practical medical reality will require minimal structural change.

The assessment takes only 13 seconds per eye using standard handheld automated pupillometers. If the protocol is successfully validated in larger, multicenter clinical trials, it could be universally adopted as a rapid, low-cost bedside tool to help intensive care teams map long-term prognoses and treatment strategies.