Bilateral Transcranial Direct Current Stimulation and Ocular Occlusion for Adults With Amblyopia

Effect of the Combination of tDCS and Visual Occlusion Therapy on Visual Acuity, Contrast Vision and Depth Vision, in Adult Patients With Amblyopia

A prospective interventional study is expected to be conducted, to test a possible new treatment for amblyopia (lazy eye syndrome). Bilateral transcranial direct current stimulation (tDCS) is a type of noninvasive brain stimulation, which may help in visual function recovery of adult patients with amblyopia. This pilot study will test the feasibility of said therapy, along with the short term effects of bilateral tDCS in visual function.

Study Overview

• Status: Terminated
• Conditions: Amblyopia
• Intervention / Treatment: Device: Bilateral transcranial direct current stimulation

Detailed Description

Theoretical Framework: Ocular occlusion treatment has been used classically and with excellent results for the treatment of amblyopia in those under 14 years of age, since in this period it has been seen that there is greater neuroplasticity, leaving little to do in the period of lower neuroplasticity, in young and adult patients with later diagnoses. Transcranial Direct Current Stimulation therapy is an emergent technique used in neurological diseases to increase neuroplasticity, by changing the resting potential of neurons. Our hypothesis is that the combination of tDCS and visual occlusion therapy is capable of increasing visual acuity, contrast sensitivity, and depth perception, in young people over 18 years of age.

Methodology: The application of a double-blind, randomized clinical trial is proposed to evaluate the application of 2 different therapies: Occlusion with bilateral tDCS, and Occlusion with tDCS sham (sham). The study subjects will be randomly assigned to a group, and one session of stimulation will be performed. Data will be analyzed using Student's t test, or Mann-Whitney test, according to the normal or non-normal distribution of the sample, respectively. Also, the change over time of the variables will be measured using the Conditional Change Model.

Expected Results: The investigators expect that visual acuity, contrast vision, and dichoptic vision in the Occlusion therapy group with bilateral tDCS will be significantly higher than the Occlusion therapy group with tDCS sham (sham).

• Study Type: Interventional
• Enrollment (Actual): 12
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Chile
  • Region Metropolitana
    • Santiago, Region Metropolitana, Chile, 8380453
      • Faculty of Medicine of University of Chile

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Prior diagnosis of Amblyopia

Exclusion Criteria:

• Ophthalmologic disease other than amblyopia
• Chronic pharmacological therapy
• Implanted medical device
• Neurologic disease or surgery history
• History of an adverse reaction to tDCS
• Pregnancy
• Not able to give informed consent

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
Sham Comparator: Sham bilateral transcranial direct current stimulation; Sham bilateral transcranial direct current stimulation consisted of 2 milliamperes (mA) of current from the anodal electrode in the amblyopic primary visual cortex to the cathodal electrode located in the fellow primary visual cortex, but the stimulation was turned off after 30 seconds. On Sham Stimulation onset, the participant's fellow eye was occluded and the participant performed a reading task for 20 minutes.	Device: Bilateral transcranial direct current stimulation; A direct current is applied with two electrodes (cathode and anode) in specific parts of the skull. In this case the anode was over the occipital area to target the amblyopic cortex, while the cathode was over the contralateral side, targeting the fellow cortex.
Experimental: Bilateral transcranial direct current stimulation; Bilateral transcranial direct current stimulation consisted of 2 mA of current from the anodal electrode in the amblyopic primary visual cortex to the cathodal electrode located in the fellow primary visual cortex and the stimulation was on for 20 minutes. On stimulation onset, the participant's fellow eye was occluded and the participant performed a reading task for 20 minutes.	Device: Bilateral transcranial direct current stimulation; A direct current is applied with two electrodes (cathode and anode) in specific parts of the skull. In this case the anode was over the occipital area to target the amblyopic cortex, while the cathode was over the contralateral side, targeting the fellow cortex.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Visual Acuity	Clarity or Sharpness in vision, measured in LogMar	1-2 hours
Visual Sensitivity	The ability to perceive differences between an object and its background, measured in percentage of contrast sensitivity.	1-2 hours
Stereopsis	the perception of depth produced by the reception in the brain of visual stimuli from both eyes in combination. Measured in degrees of arc.	1-2 hours
Visual evoked potentials	The electroencephalographic response from the primary visual cortex to a stimuli. Measured in millivolts (mV).	1-2 hours

Collaborators and Investigators

• Sponsor: University of Chile
• Investigators: Principal Investigator: Romulo A Fuentes Flores, PhD, University of Chile

Study record dates

Study Major Dates

• Study Start (Actual): November 5, 2019
• Primary Completion (Actual): January 31, 2020
• Study Completion (Actual): January 31, 2020

Study Registration Dates

• First Submitted: August 13, 2021
• First Submitted That Met QC Criteria: August 20, 2021
• First Posted (Actual): August 23, 2021

Study Record Updates

• Last Update Posted (Actual): August 23, 2021
• Last Update Submitted That Met QC Criteria: August 20, 2021
• Last Verified: August 1, 2021

More Information

Terms related to this study

• Keywords: Amblyopia; Transcranial direct current stimulation; Lazy eye syndrome; Ocular occlusion
• Additional Relevant MeSH Terms: Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Eye Diseases; Neurologic Manifestations; Sensation Disorders; Vision Disorders; Amblyopia
• Other Study ID Numbers: CECI-HCUCH Nº44-2019

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: No
• product manufactured in and exported from the U.S.: No