Pupillary diameter monitoring is currently used routinely for assessment of the nociception / antinociception balance during surgery.

Pupillary diameter decreases reflexively in response to light flash, called photomotor reflex. The photomotor reflex is described by the latency between the light flash and the beginning of the decay expressed in milliseconds, the slope or decay rate expressed in millimeters per second, and the percentage of variation, corresponding to the ratio between the basal pupil diameter and the minimum diameter reached during the light stimulation.

The AlgiScan™ videopupillometer used includes a device for producing a flash light, designed for this purpose.

It has recently been shown that the slope (or rate) of pupillary diameter decrease during a light flash varies during anesthesia, independently of any nociceptive stimulus.

The hypothesis of this study is the variation of the decay slope of the pupil diameter is proportional to the depth of the anesthesia.

Inclusion Criteria:

• Majors patients
• Score American Society of Anesthesiologists (ASA) 1 or 2
• Managed in the operating theater of the University Hospital of Saint-Etienne for a neurosurgical intervention.

Exclusion Criteria:

• Single or bilateral eye surgery modifying the possibilities of variation of the pupillary diameter
• Having been asleep under general anesthesia in the 7 days prior to the current surgery
• History of Parkinson's disease, insulin-dependent or non-insulin-dependent diabetes at a dysautonomic stage or chronic alcoholism at a dysautonomous stage

Patients who have a neurosurgical intervention will be included.