Chromatic Retinal Stimulation to Reduce Chronic Pain and Pain Sensitivity

Study Overview
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Brief Summary
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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.

Official Title
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Chromatic Retinal Stimulation to Reduce Chronic Pain and Pain Sensitivity

Conditions
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Chronic Low-back Pain, Chronic Pain, Fibromyalgia

Intervention / Treatment
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* Other: Green Light stimulation
* Other: Equal Energy White stimulation
* Other: S-cone modulating white light


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Adults greater than or equal to 18. Individuals who have been diagnosed with fibromyalgia or chronic low back pain by their physician. Individuals who experience an average pain severity greater than 7/10 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. Exclusion Criteria: Vision disorders or conditions resulting in severe vision impairment or blindness Individuals with self-report of color blindness Alert and oriented, and able to provide informed consent Ability to read and speak English to complete validated questionnaires. 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

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Equal energy white stimulus<br>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. | Other: Equal Energy White stimulation<br>* A portable battery-operated ganzfeld light stimulation device will be used to deliver white light for 2 hours per day for 5 consecutive days.<br>|
| Experimental: Green light stimulus<br>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. | Other: Green Light stimulation<br>* A portable battery-operated ganzfeld light stimulation device will be used to deliver green light for 2 hours per day for 5 consecutive days.<br>|
| Experimental: S-cone modulating white light<br>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. | Other: S-cone modulating white light<br>* A portable battery-operated ganzfeld light stimulation device will be used to deliver S-cone modulating light for 2 hours per day for 5 consecutive days.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Feasibility: Percent follow-up | Percent follow-up for 1 week baseline visit. Follow-up greater than 70% will be considered feasible. | 1 week | 
| Feasibility: Percent of flash surveys completed | 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. | 1 week | 
| Feasibility: Self-reported light stimulation sessions completed | 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. | 1 week | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in pain intensity after stimulation | Pain intensity measured by a 0-10 numeric rating scale for overall pain. 0 represents no pain, and 10 represents the worst pain imaginable. | Baseline, 1 week | 
| Change in pressure pain threshold | 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. | Baseline, 1 week | 
| Change in Conditioned Pain modulation | 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. | Baseline, 1 week | 
| Change in Temporal Summation | 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. | Baseline, 1 week | 
| Change in activity measured with an accelerometer | 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. | 1 week prior to baseline and 1 week during light stimulation |