Pilot Study of TENS for Ocular Pain

A Pilot Study of the Safety and Feasibility of Transcutaneous Electrical Nerve Stimulation (TENS) for Chronic Ocular Pain

Approximately 20% of Veterans have a diagnosis of dry eye (DE) syndrome which is often accompanied by ocular pain that significantly impacts activities of daily living. Currently very few treatments are available for chronic ocular pain, likely because the mechanisms underlying this type of pain have only recently begun to be studied. New treatments that target the neuropathic mechanisms contributing to this type of pain are needed. The proposed research provides a crucial step in addressing the lack of treatments for neuropathic ocular pain by validating the methodology needed to support a randomized controlled trial of transcutaneous electrical nerve stimulation (TENS). TENS is a non-pharmacologic, non-addictive, non-invasive treatment that has been shown to be effective in other chronic pain conditions. The present pilot study aims to address the need for preliminary support of safety and efficacy of TENS for ocular pain, t to advance the study of new treatments for the long-term relief of chronic ocular pain and its impact on health.

Study Overview

• Status: Completed
• Conditions: Eye Pain
• Intervention / Treatment: Device: High frequency forehead TENS; Device: Low frequency forehead TENS

• Study Type: Interventional
• Enrollment (Actual): 39
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Florida
    • Miami, Florida, United States, 33125
      • Miami VA Healthcare System, Miami, FL

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 14 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• male or female
• all races and ethnicities
• at least 18 years of age
• persistent eye pain for at least 6 months
• average eye pain intensity of 4 or more on a 0-10 numerical rating scale
• on a stable medication regimen for at least the past 3 months
• naïve to TENS use for orofacial conditions
• eye pain having neuropathic-like characteristics

Exclusion Criteria:

• presence of ocular diseases that are the likely cause of pain (i.e., corneal and conjunctival scarring, corneal edema, uveitis, iris transillumination defects, etc.)
• contraindication to TENS (i.e., pacemaker, cardioverter defibrillator, neuro-stimulation (brain or spinal cord), bone growth stimulations, indwelling blood pressure monitors, epilepsy, pregnancy)
• patients with confirmed signs of tear dysfunction
• current participation in another study with an investigational drug or device within one month prior to screening

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: high frequency TENS; high frequency (60Hz) TENS delivered for 20 minutes to the forehead; at least 3 times per week in-home; for 6 months.	Device: High frequency forehead TENS; Transcutaneous electrical nerve stimulation (TENS) device with electrode placement at the forehead. Biphasic rectangular impulses at 60Hz frequency will be delivered for a maximum of 20 minutes at a maximum amplitude of 16mA. Participant may halt amplitude before it reaches maximum amplitude. The device has previously been cleared by the FDA for use in migraine patients.
Active Comparator: low frequency TENS; low frequency (3Hz) TENS delivered for 20 minutes to the forehead; at least 3 times per week in-home; for 6 months.	Device: Low frequency forehead TENS; Transcutaneous electrical nerve stimulation (TENS) device with electrode placement at the forehead. A 3Hz biphasic square wave will be delivered for 20 minutes up to a maximum amplitude of 16mA.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Reported Device-related Side-effects	An open-ended question of side-effects will be used to assess any bothersome changes in physical or mental health symptoms every 2 weeks during the 6-month at-home course of treatment. Presence, description of symptom, severity of symptoms, participant assessment of device/treatment-relatedness of symptoms, and desire or actual discontinuation of device use will be recorded.	6 months
Time to Peak Change in Numerical Rating Scale (NRS, 0-10)	Calculation of time (weeks) to peak reduction in eye pain will be made based on NRS scores obtained every two weeks after initiation of intervention protocol.	6 months
Number of Screen Failures	The number of individuals who meet pre-screening requirements, consent to study procedures, but who do not meet full criteria after screening visit is conducted	6 months
Treatment Compliance Rate	Count of the number (and calculated percentage) of individuals who reported completing at least 75% of treatment sessions.	6 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage of Individuals Who Score 100% on Checklist for Proper Use of TENS Device	The percentage of individuals who, after instruction, score 100% on checklist items for safe and proper use of the device.	baseline
Rate of Uncertainty in Participant Treatment Allocation Guess	Percentage of individuals who rate at least moderate uncertainty in guessing which treatment arm they were allocated to.	6 months

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Beta Coefficients for Participant Demographics (Sex, Age, Race/Ethnicity) in Regression Model Predicting Adherence to Treatment Protocol	Exploratory regression analysis to identify associations between demographic variables and number of treatment sessions completed	1 year
Beta Coefficients for Participant Demographics (Sex, Age, Race/Ethnicity) in Regression Model Predicting Change in Pain (Numerical Rating Scale)	Exploratory regression analysis to identify associations between demographic variables and change in pain ratings (before vs. after 6 month TENS treatment)	1 year

Collaborators and Investigators

• Sponsor: VA Office of Research and Development
• Investigators: Principal Investigator: Elizabeth R Felix, PhD, Miami VA Healthcare System, Miami, FL

Publications and helpful links

General Publications

• Shields C, Qazi S, Zaldivar A, Cabrera K, Mangwani-Mordani S, Peterson H, Bhatt S, Tang F, Galor A, Felix ER. Randomized Pilot Study of Transcutaneous Electrical Nerve Stimulation for Neuropathic/Nociplastic Ocular Pain. Am J Ophthalmol. 2026 Jun;286:318-331. doi: 10.1016/j.ajo.2026.03.008. Epub 2026 Mar 10.

Study record dates

Study Major Dates

• Study Start (Actual): October 3, 2022
• Primary Completion (Actual): November 30, 2024
• Study Completion (Actual): November 30, 2024

Study Registration Dates

• First Submitted: August 30, 2022
• First Submitted That Met QC Criteria: September 2, 2022
• First Posted (Actual): September 8, 2022

Study Record Updates

• Last Update Posted (Actual): June 10, 2026
• Last Update Submitted That Met QC Criteria: May 14, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Dry Eye; Neuropathic Pain; Transcutaneous Electrical Nerve Stimulation; Eye pain
• Additional Relevant MeSH Terms: Pain; Neurologic Manifestations; Nervous System Diseases; Neuromuscular Diseases; Peripheral Nervous System Diseases; Eye Diseases; Lacrimal Apparatus Diseases; Eye Manifestations; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Neuralgia; Dry Eye Syndromes; Eye Pain
• Other Study ID Numbers: F3883-P

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: No