Effect of Transcranial Magnetic Stimulation on Visual Functions of Adult Amblyopia: a Preliminary Study

NCT05393739 | Recruiting

• 1 other identifier: 202106139DINC
• Study Type: interventional
• Target: 30
• Locations: 1 country
• Sites: 1

Brief Summary

Amblyopia, with a prevalence rates of 3% in adult population, is a common cause of vision impairment. It is characterized by impaired vision in one or both eyes because of disruption of normal visual stimuli and underdevelopment of the visual cortex, leads to lifelong visual deficits affecting both monocular and binocular visual function. Common causes of amblyopia include refraction error, anisometropia, strabismus and visual deprivation arising from ptosis or congenital cataract. Our previous studies had shed light on the relationship between abnormal early visual experience, and development of later amblyopia and possible neural developmental disorders. Functional recovery is difficult when neuroplasticity slows down at the end of the critical period. To date, there is no established effective treatment for adult amblyopia. Repetitive transcranial magnetic stimulation (rTMS) is one of the non-invasive stimulations had been used widely as a research tool to understand the brain functions and an established treatment modality in neuropsychiatric diseases. Theta burst stimulation (TBS) is a newer form of rTMS protocol which have a major advantage over traditional rTMS in their reduced administration duration and allowing stimulation at significantly lower intensities to attain comparable effects. TBS had been demonstrated to able to improve functions in participants with visual disorders. However, studies of its use on adult amblyopia are scarce. Due to lack of efficient treatment at present, it is of scientific significance to conduct placebo-controlled experiments on this topic. Investigators will evaluate the effect of three regimens of TBS (intermittent, continuous and sham), after one session and accumulative sessions, on visual functions of amblyopia adults shortly after treatment and 2 weeks later (lasting effect), in order to evaluate its potential role in amblyopia and find out the best paradigm for amblyopia treatment.

Conditions

Amblyopia

Keywords

Transcranial magnetic stimulation; Amblyopia; Neuroplasticity

Outcome Measures

Primary Outcomes (1)

• Objective

  Change from baseline best corrected visual acuity: distance visual acuity measured for each eye at a distance of 6 m. Visual acuity scored letter-by-letter instead and lonarithm of the minimum angle of resolution (logMAR) scores were recored.

  1 month for each participant

Study Arms (3)

Intermittent theta burst

EXPERIMENTAL

The total TBS time is about 1 to 3 minutes and the subjects have to look at at a visual stimulus on a computer monitor while receiving TBS and continue the visual training until 20 minutes after the treatment. In iTBS group, the subjects look at the visual stimulus with amblyopic eye while in cTBS group, subjects look at visual stimulus with non-amblyopic eye. The subjects will receive three times of stimulations in one week. The visual function evaluation includes BCVA, contrast sensitivity and stereoacuity. Visual functions will be evaluated right after TBS session (t1). Participant will receive same type of treatment for another 2 times within one week followed by visual function tests (t2). To evaluate the long-term effect, participants will be followed for another visual function tests (t3) after 2 weeks.

Device: Theta burst transcranial magnetic stimulation (TBS) procedure

Continuous theta burst

EXPERIMENTAL

The total TBS time is about 1 to 3 minutes and the subjects have to look at at a visual stimulus on a computer monitor while receiving TBS and continue the visual training until 20 minutes after the treatment. In iTBS group, the subjects look at the visual stimulus with amblyopic eye while in cTBS group, subjects look at visual stimulus with non-amblyopic eye. The subjects will receive three times of stimulations in one week. The visual function evaluation includes BCVA, contrast sensitivity and stereoacuity. Visual functions will be evaluated right after TBS session (t1). Participant will receive same type of treatment for another 2 times within one week followed by visual function tests (t2). To evaluate the long-term effect, participants will be followed for another visual function tests (t3) after 2 weeks.

Device: Theta burst transcranial magnetic stimulation (TBS) procedure

Sham theta burst

SHAM COMPARATOR

The stimulus intensity in sham group is about half of that in iTBS/cTBS groups, and the subjects receive a placebo stimulation with the coil orientation tilted to 90°. The visual function evaluation includes BCVA, contrast sensitivity and stereoacuity. Visual functions will be evaluated right after TBS session (t1). Participant will receive same type of treatment for another 2 times within one week followed by visual function tests (t2). To evaluate the long-term effect, participants will be followed for another visual function tests (t3) after 2 weeks.

Device: Theta burst transcranial magnetic stimulation (TBS) procedure

Interventions

Theta burst transcranial magnetic stimulation (TBS) procedure DEVICE

The procedure includes determining the specific occipital point at which place the stimulation coil; this corresponds to the area where magnetic stimulation is most capable of inducing phosphenes or transient visual phenomena. The phosphenes are directly induced by stimulation of the visual cortex and their presence indicates that the magnetic stimulation is in the correct location. The subjects would wear a personalized swimming cap with the determined area for stimulation marked on it. The major differences between iTBS and cTBS are the frequency and interval of stimulus.

Continuous theta burst; Intermittent theta burst; Sham theta burst

Eligibility Criteria

• Age: 20 Years - 50 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64)

You may qualify if:

• Adult amblyopia participants, aged 20-50 years old.
• An amblyogenic factor and history of amblyopia treatment was recorded

You may not qualify if:

• Unstable vital sign
• History of brain injury and/or head trauma
• Neurological and psychiatric disease
• Seizures or family history of seizure
• Pregnancy
• Uncontrolled migraine or the presence of metallic implants or shunt in the head or torso
• Wide region of ischemic cicatrix, multiple sclerosis, taking tricycle antidepressants,
• Analgesics or any drugs may decrease the threshold for inducing seizure
• Experienced sleep disorders during the rTMS treatment
• Severe alcoholism or taking seizure drugs
• Severe heart diseases or uncontrollable migraine caused by high intracranial pressure

Sponsors & Collaborators

• National Taiwan University Hospital: lead

Study Sites (1)

National Taiwan University Hospital

Taipei County, 100225, Taiwan

RECRUITING

MeSH Terms

Conditions

Amblyopia

Condition Hierarchy (Ancestors)

Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Vision Disorders; Sensation Disorders; Neurologic Manifestations; Eye Diseases; Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Study Officials

• Tzu-Hsun Tsai

  National Taiwan University Hospital

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Tzu-Hsun Tsai, PhD

CONTACT

886223123456; lucia_tsai@yahoo.com.tw

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: PARTICIPANT
• Purpose: HEALTH SERVICES RESEARCH
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: May 2, 2022
• First Posted: May 26, 2022
• Study Start: January 5, 2023
• Primary Completion: December 31, 2025
• Study Completion: December 31, 2025
• Last Updated: June 22, 2025

Record last verified: 2025-06

Locations

TW (1)