Pupil Dilation and Analgesia Nociception Index

Do Pupil Dilation and Analgesia Nociception Index Reflect Pain: a Pilot Study in Healthy, Conscious Volunteers

Status

Completed

Phases

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT03280238

Enrollment

Registered

2017-09-12

Start date

2017-03-01

Completion date

2017-05-31

Last updated

2017-09-13

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Pain

Brief summary

Pain assessment is crucial in clinical practice. Currently, subjective self-report is considered the most appropriate method to evaluate pain. Although several methods to assess pain objectively exist, the lack of a golden standard still remains. This pilot study assesses the changes in pupil dilation (PD) and the analgesia nociception index (ANI) as a measure of pain in healthy, conscious, male volunteers in a highly standardized and individualized environment. Nineteen subjects received three blocks of 4 individualized electrical stimulus intensities, ranging from no to severe pain. Subjects reported their perceived severity of each individual stimulus, enabling the comparison of changes in PD and ANI in relation to both administered stimulus intensities and perceived pain severities. PD and ANI were measured before and after each administration of a stimulus.

Interventions

DIAGNOSTIC_TESTMeasurement of pupil dilation and analgesia nociception index

painful electrical stimuli of various intensities were administered to the subjects after which changes in pupil diameter and analgesia nociception index were measured

Study design

Allocation

Intervention model

SINGLE_GROUP

Primary purpose

DIAGNOSTIC

Masking

NONE

Eligibility

Sex/Gender

MALE

Age

18 Years to 35 Years

Healthy volunteers

Yes

Inclusion criteria

* good health * no acute or chronic pain conditions * well rested

Exclusion criteria

* chronic treatment * bad health * daily use of analgetics or other medication * weekly tobacco use * weekly use of recreational drugs * more than 10 alcohol consumptions a week

Design outcomes

Primary

Measure	Time frame	Description
Pupil dilation in relation to pain	2sec before until 4sec after each painful stimulus	measurement of pupil dilation

Secondary

Measure	Time frame	Description
Analgesia nociception index in relation to pain	30sec before until 60sec after each painful stimulus	measurement of analgesia nociception index

Countries

Belgium

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Feb 4, 2026