Effects of Transcranial Direct Current Stimulation (tDCS) in Chronic Corneal Pain

Study Overview
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Brief Summary
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In this study the investigators aim to examine the effects of Transcranial Direct Current Stimulation (tDCS) on pain levels as well as the changes in cognitive (thought) processing in individuals with chronic pain of the cornea -- and also compared with healthy controls.

Official Title
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Neural Correlates of Pain-related Cognitive Processing in Chronic Pain of the Cornea: an ERP and Electrical Stimulation Study.

Conditions
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Corneal Pain, Chronic Pain, Neuropathic Pain

Intervention / Treatment
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* Device: Transcranial Direct Current Stimulation (tDCS)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria (for all subjects): Provide informed consent to participate in the study; 18 to 65 years old; Additional Inclusion Criteria for Subjects with Chronic Corneal Pain: Corneal pain for six months or more; Referral from a corneal specialist (Dr. Perry Rosenthal) with refractoriness to conventional ophthalmologic treatments for corneal pain such as local topical medications and soft bandage contact lenses; Report a Visual Analogue Scale (VAS) for pain of 4 or greater in the previous 3 weeks; Exclusion Criteria (for all subjects): History of alcohol or substance abuse within the last 6 months as self-reported; Diagnosis of any neurological diseases (such as epilepsy); Episodes of seizures within the last 6 months; Unexplained loss of consciousness Use of carbamazepine or neuropsychotropic drugs Contraindications to tDCS Metal in the head Implanted brain medical devices Pregnant at time of enrollment

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Active tDCS<br>Subjects will undergo 20 minutes of active tDCS stimulation. | Device: Transcranial Direct Current Stimulation (tDCS)<br>* Subjects will undergo 2 sessions of 20 minutes of tDCS stimulation (either active or sham)in a randomized order - each session will be separated by at least one week to prevent carry-over effects.<br>* Other names: 1x1 direct current stimulator; Soterix Medical;|
| Sham Comparator: Sham tDCS<br>Subjects will undergo 20 minutes of sham tDCS stimulation. | Device: Transcranial Direct Current Stimulation (tDCS)<br>* Subjects will undergo 2 sessions of 20 minutes of tDCS stimulation (either active or sham)in a randomized order - each session will be separated by at least one week to prevent carry-over effects.<br>* Other names: 1x1 direct current stimulator; Soterix Medical;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in pain scales | We will measure changes in the visual analogue scale (VAS) for pain, and also measure pain threshold (using an algometer) before and after each stimulation session. We will compare the measurements from before stimulation to after stimulation, in each scheduled session, as this study is measuring the effects of a single session of tDCS. | Measured for approximately 2 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in EEG measurements | We will measure changes in event related potentials (ex. P300, mismatch negativity) recorded via electroencephalography (EEG) before and after each stimulation session. We will compare the measurements from before stimulation to after stimulation, in each scheduled session, as this study is measuring the effects of a single session of tDCS. | Measured for approximately 2 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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transcranial stimulation, direct current stimulation