Alternating and Direct Current Stimulation for Neuropathic Eye Pain

Study Overview
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Brief Summary
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The goal of this clinical intervention is to test if two forms of transcranial current stimulation, transcranial direct current stimulation (tDCS) or transcranial alternating current stimulation (tACS) can alleviate neuropathic eye pain in a sample of 20 patients. The main aims are: Test if tDCS/tACS can alleviate neuropathic eye pain and/or other cerebral symptoms: brain fatigue, migraine, light sensitivity, etc. Test if one stimulation method is superior to the other Patients will be treated for a total of fifteen 30-minute stimulation sessions, three times a day over a five-day period, each stimulation separated by approximately 4 hours, with either active tACS or tDCS over the scalp corresponding to primary sensory and motor areas. The patients will have questionnaires to monitor subjective experiences and pupillometry before and after treatment to monitor experimental outcomes.

Detailed Description
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Brief Summary sufficient

Official Title
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Alternating and Direct Current Stimulation for the Treatment of Chronic Neuropathic Eye Pain and Cerebral Symptoms: a Pilot Study

Conditions
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Eye Pain, Neuropathy, Optic, Cerebral Injury

Intervention / Treatment
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* Device: DC-Stimulator Plus (NeuroConn GmbH, Germany)
* Device: Sooma direct current stimulator (Sooma, Finland)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: persistent eye pain for at least 6 months average eye pain intensity of 4 or more on a 0-10 numerical rating scale naive to transcranial stimulation eye pain having neuropathic-like characteristics Exclusion Criteria: contraindication to transcranial stimulation (i.e., pacemaker, cardioverter defibrillator, neuro-stimulation (brain or spinal cord), bone growth stimulations, indwelling blood pressure monitors, epilepsy, pregnancy) presence of ocular diseases that are the likely cause of pain (i.e., corneal and conjunctival scarring, corneal edema, uveitis, iris transillumination defects, etc.) current participation in another study with an investigational drug or device within one month prior to screening

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: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Transcranial alternating current stimulation<br>Transcranial alternating current stimulation (tACS) device using 50x70 mm electrodes that are placed bilaterally between EEG coordinates C3/C5 for left hemisphere and C4/C6 for right hemisphere (corresponding to S1 and M1 of the eye). The alternating current electrodes are in-phase and have the same peak to peak stimulation 3mA, for 30 minutes duration at 10Hz. An impedance value under 15 ohms is required at all times to ensure patient comfort and safety. | Device: DC-Stimulator Plus (NeuroConn GmbH, Germany)<br>* Transcranial alternating current stimulation<br>|
| Experimental: Transcranial direct current stimulation<br>Transcranial direct current stimulation (tDCS) device using 50x70 mm electrodes that has the anodal electrode placed contralateral to most prominent ocular pain or, in the case of bilateral pain symptoms, contralateral to the dominant hand between EEG coordinates C3/C5 for left hemisphere and C4/C6 for right hemisphere (corresponding to S1 and M1 of the eye), and the cathode placed on the patient's upper arm. A current peaking at 3mA will ramp up for 20 secs and be delivered for a total of 20 minutes, thereafter, ramping down for 20s. An impedance value under 15 ohms is required at all times to ensure patient comfort and safety. | Device: Sooma direct current stimulator (Sooma, Finland)<br>* Transcranial direct current stimulation<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from baseline subjective pain via neuropathic pain symptom inventory for the eye (NPSI-eye) at 1 week | Assesses pain related symptoms on a scale from 0 indicating no pain (better outcome) to10 indicating worst pain imaginable (worse outcome) | through treatment completion, 1 week | 
| Change from baseline subjective pain via neuropathic pain symptom inventory for the eye (NPSI-eye) at 2 weeks | Assesses pain related symptoms on a scale from 0 indicating no pain (better outcome) to10 indicating worst pain imaginable (worse outcome) | through treatment completion, 2 weeks | 
| Change from baseline subjective pain via neuropathic pain symptom inventory for the eye (NPSI-eye) at 1 month | Assesses pain related symptoms on a scale from 0 indicating no pain (better outcome) to10 indicating worst pain imaginable (worse outcome) | through treatment completion, 1 month | 
| Change from baseline subjective pain effect experiences via Defense and Veteran Pain Rating Scale (DVPRS) at 1 week | Assesses pain related symptoms effecting sleep, stress, disposition, life quality, on a scale from 0 indicating no effect (better outcome) to10 indicating maximum effect (worse outcome) | through treatment completion, 1 week | 
| Change from baseline subjective pain effect experiences via Defense and Veteran Pain Rating Scale (DVPRS) at 2 weeks | Assesses pain related symptoms effecting sleep, stress, disposition, life quality, on a scale from 0 indicating no effect (better outcome) to10 indicating maximum effect (worse outcome) | through treatment completion, 2 weeks | 
| Change from baseline subjective pain effect experiences via Defense and Veteran Pain Rating Scale (DVPRS) at 1 month | Assesses pain related symptoms effecting sleep, stress, disposition, life quality, on a scale from 0 indicating no effect (better outcome) to10 indicating maximum effect (worse outcome) | through treatment completion, 1 month | 
| Change from baseline subjective mental symptoms via Mental Fatigue Scale (MFS) at 1 week | Assesses mental symptoms on a scale from 0 indicating no effect (better outcome) to 3 indicating extreme effect (worse outcome) | through treatment completion, 1 week | 
| Change from baseline subjective mental symptoms via Mental Fatigue Scale (MFS) at 2 weeks | Assesses mental symptoms on a scale from 0 indicating no effect (better outcome) to 3 indicating extreme effect (worse outcome) | through treatment completion, 2 weeks | 
| Change from baseline subjective mental symptoms via Mental Fatigue Scale (MFS) at 1 month | Assesses mental symptoms on a scale from 0 indicating no effect (better outcome) to 3 indicating extreme effect (worse outcome) | through treatment completion, 1 month | 
| Change from baseline subjective ocular symptoms and symptom frequency via custom ocular pain questionnaire at 1 week | Ocular pain questionnaire using a visual analog scale with 0 indicating no pain (better outcome) and 10 indicating extreme pain (worse outcome) and frequency measure from 0% indicating never occurring (better outcome) to 100% indicating always occurring (worse outcome) | through treatment completion, 1 week | 
| Change from baseline subjective ocular symptoms and symptom frequency via custom ocular pain questionnaire at 2 weeks | Ocular pain questionnaire using a visual analog scale with 0 indicating no pain (better outcome) and 10 indicating extreme pain (worse outcome) and frequency measure from 0% indicating never occurring (better outcome) to 100% indicating always occurring (worse outcome) | through treatment completion, 1 month | 
| Change from baseline subjective ocular symptoms and symptom frequency via custom ocular pain questionnaire at 1 month | Ocular pain questionnaire using a visual analog scale with 0 indicating no pain (better outcome) and 10 indicating extreme pain (worse outcome) and frequency measure from 0% indicating never occurring (better outcome) to 100% indicating always occurring (worse outcome) | through treatment completion, 1 month | 
| Number of patients with treatment-related adverse events as assessed by ocular pain questionnaire | Ocular pain questionnaire using a visual analog scale with 0 indicating no pain (better outcome) and 10 indicating extreme pain (worse outcome) and frequency measure from 0% indicating never occurring (better outcome) to 100% indicating always occurring (worse outcome) | through treatment completion, 1 month | 
| Change from baseline pupil diameter in millimeters at 1 week | Minimum and maximum pupil diameter in millimeters | through treament completion, 1 week | 
| Change from baseline pupil velocity in millimeters per second at 1 week | Pupil change velocity in millimeters per second | through treament completion, 1 week | 
| Change from baseline pupil latency in milliseconds at 1 week | Pupil latency latency in milliseconds | through treament completion, 1 week | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Treatment compliance rate | Evaluation of completed treatment from a total of 15 | through study completion, 1 year |