Chromatic Retinal Stimulation to Reduce Chronic Pain and Pain Sensitivity

Not Applicable

Recruiting

• Conditions: Fibromyalgia; Chronic Low-back Pain; Chronic Pain
• Interventions: Device: Equal Energy White stimulation; Device: S-cone modulating white light; Device: Green Light stimulation

• Registration Number: NCT05956067
• Lead Sponsor: University of North Carolina, Chapel Hill

Brief Summary

Participants with chronic pain conditions including chronic low back pain and fibromyalgia may benefit from light stimuli presented to the retina to reduce chronic pain severity and pain sensitivity. Participants will be recruited into this study and will be presented with one of three uniform light stimuli via a wide-field ganzfeld in three conditions to determine the retinal mechanisms that reduce pain. This work will lead to a greater understanding of retinal mechanisms that contribute to pain and will assist the design of future studies to harness the potential of light based pain therapies.

Detailed Description

Not available

Study Timeline

• Study First Submitted: 2023-06-28
• Study First Submitted QC: 2023-07-13
• Study First Posted: 2023-07-21
• Study Start: 2023-08-25
• Status Verified: 2023-10
• Last Update Submitted: 2024-06-12
• Last Update Posted: 2024-06-14
• Primary Completion: 2025-07-17
• Study Completion: 2025-07-29

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 60

Inclusion Criteria

• Adults greater than or equal to 18 and less than or equal to 65.
• Individuals who have been diagnosed with fibromyalgia or chronic low back pain by their physician.
• Individuals who experience an average pain severity greater than 4/10 in intensity at baseline.
• Willingness to wear a battery-operated portable ganzfeld light stimulator device for 2 hours per day at the same time each day (ideally complete the light therapy session between 5 am-10 am each morning) for 5 days.
• Alert and oriented, and able to provide informed consent
• Ability to read and speak English to complete validated questionnaires.

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Exclusion Criteria

• Vision disorders or conditions resulting in severe vision impairment or blindness
• Individuals with self-report of color blindness
• Prisoner Status
• Pregnancy
• No other history or condition that would, in the investigator's judgment, indicate that the patient would very likely be non-compliant with the study or unsuitable for the study (e.g., might interfere with the study, confound interpretation, or endanger the patient).
• History of seizure disorder

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Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Equal energy white stimulus	Equal Energy White stimulation	Equal energy white light at 500 lux. The International Commission on Illumination (CIE) coordinates of this light are (x=y=0.33), indicating that the stimulus appears uniformly white which means that the activation of each of the three classes of photoreceptors are equivalent, thus silencing any chromatic opponency. The stimulus will be delivered by a portable battery-operated ganzfeld light stimulation device for 2 hours per day for 5 consecutive days.
S-cone modulating white light	S-cone modulating white light	The S-cone modulating light stimulus will alternate between two light conditions at 500 lux that will activate the S-cones by about 100x differentially between the two conditions while maintaining the L- an M-cones at constant activation between the two alternating conditions using 427 nm versus 545 nm light. The stimulus will be delivered by a portable battery-operated ganzfeld light stimulation device for 2 hours per day for 5 consecutive days.
Green light stimulus	Green Light stimulation	Green light at 500 lux. Participants will view 545 nm green light delivered via a portable battery-operated ganzfeld light stimulation device for 2 hours per day for 5 consecutive days.

Primary Outcome Measures

Name	Time	Method
Feasibility: Percent of flash surveys completed	1 week	Percent of flash surveys completed during light stimulation period. 0% is the lowest and 100% is the highest. Higher percentages indicate greater percent of flash surveys completed.
Feasibility: Percent follow-up	1 week	Percent follow-up for 1 week baseline visit. Follow-up greater than 70% will be considered feasible.
Feasibility: Self-reported light stimulation sessions completed	1 week	Self-reported light stimulation sessions completed by flash survey administered after each light stimulation session over the 5 day stimulation period. Number of sessions will be reported the minimum is 0 and the maximum is 5.

Secondary Outcome Measures

Name	Time	Method
Change in Temporal Summation	Baseline, 1 week	Temporal Summation. The investigators will evaluate temporal summation using a 40g Neuropen applied to the skin of the volar forearm and lumbar region, following a train of 10 identical stimuli (1 Hz). Participants will report retrospectively, the pain intensity of the 1st and 10th pinprick using a 0-10 numerical rating scale (NRS). 0 is the minimum and 10 is the maximum pain intensity that will be reported.
Change in pain intensity after stimulation	Baseline, 1 week	Pain intensity measured by a 0-10 numeric rating scale for overall pain. 0 represents no pain, and 10 represents the worst pain imaginable.
Change in pressure pain threshold	Baseline, 1 week	Pressure Pain Threshold is the threshold in which pain is experienced in response to increasing force applied to the trapezius measured by a pressure algometer in kilograms of force per square centimeter (kgf/cm\^2). The higher the value, the higher the threshold. The maximum is 10 kgf/cm\^2 and minimum is 0.
Change in Conditioned Pain modulation	Baseline, 1 week	Conditioned Pain modulation magnitude will be calculated as the difference in mean pressure pain threshold (kgf/cm\^2) measured prior to and during the conditioning stimulus (cold water bath), with increases in pressure pain threshold during conditioning interpreted as evidence of efficient endogenous pain inhibition.
Change in activity measured with an accelerometer	1 week prior to baseline and 1 week during light stimulation	Activity will be measured by an accelerometer. Average daily step count for the duration of the stimulus. Average non-sedentary time in minutes will able be determined over the stimulation period and compared to the data collected over the 1 week run-in period.

Trial Locations

Locations (1)

University Of North Carolina; 🇺🇸 Chapel Hill, North Carolina, United States