Effect of Green Light Exposure at Different Times on the Pain of Subjects

The Second Affiliated Hospital of Chongqing Medical University140 enrolled

Overview

This study investigated the effects of green-light exposure on pain sensitivity in healthy volunteers and on perioperative pain in surgical patients. Healthy volunteers underwent 30-min green-light exposure at three different times of day (08:00-09:00, 12:00-13:00, and 16:00-17:00) on separate days using a within-subject design, with a washout period of at least 2 days between sessions. Surgical patients undergoing elective surgery under general anesthesia with preoperative arterial puncture were randomly assigned in a 1:1 ratio to either a green-light intervention group or a sham-device control group. The assigned intervention was initiated before arterial puncture and continued throughout surgery. The effects of green-light exposure on pain sensitivity, procedural pain, and perioperative pain were evaluated.

The study consisted of two components. In the healthy-volunteer component, participants underwent a 30-min green-light exposure at three different times of day (08:00-09:00, 12:00-13:00, and 16:00-17:00) on separate days in a within-subject design, with a washout period of at least 2 days between sessions. Pain threshold, pain tolerance, and cold pain sensitivity were assessed before and after each exposure. In the surgical component, eligible patients were randomly assigned in a 1:1 ratio to either the green-light intervention group or the sham-device control group using a computer-generated random sequence. Participants wore identical wearable GLED glasses for 30 min before arterial puncture and throughout surgery. In the intervention group, the device delivered 511-515 nm green light at 100 lux; in the control group, the device remained powered off and participants were exposed only to ambient room light. Care providers, investigators not involved in intervention administration, and clinical outcome assessors were blinded to group allocation. Personnel responsible for device allocation and administration were unblinded and were not involved in perioperative clinical care or outcome assessment.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

PREVENTION

Masking

Eligibility

Sex: ALLMin age: 18 YearsMax age: 65 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria Healthy volunteers: 1. Age 18-65 years. 2. ASA physical status I. 1\. Age 18-65 years. 2. ASA physical status I-III. 3. Scheduled for elective abdominal surgery under general anesthesia requiring arterial puncture. Exclusion Criteria： 1. Skin ulceration, dermatitis, or allergic reactions at the study site. 2. Chronic use of analgesics or psychiatric medications. 3. Color blindness or uncorrected cataracts. 4. Severe cardiovascular, respiratory, or inflammatory diseases. 5. Failure of the initial arterial puncture attempt (surgical cohort only). 6. Inability to communicate or provide informed consent.

Outcomes

Primary Outcomes

Pain intensity during arterial puncture

Numeric Rating Scale (NRS), ranging from 0 to 10, with higher scores indicating greater pain intensity.

Time frame: The pain score during arterial puncture

Secondary Outcomes

Pain sensitivity

Pain sensitivity was assessed using pressure pain threshold and pressure pain tolerance measured with an algometer. In healthy volunteers, cold pain sensitivity was additionally assessed using a cold test.

Time frame: Immediately before and 30 minutes after light exposure

Analgesic consumption during surgery

assessed by the actual dose of analgesic during the surgery

Time frame: From surgery beginning to the ending of the surgery

Pain intensity after surgery

Numeric Rating Scale (NRS), ranging from 0 to 10, with higher scores indicating greater pain intensity.

Time frame: From ending of the surgery to 24 hours after surgery

Analgesic consumption after surgery

assessed by the actual dose of analgesic after surgery