Glaucoma is a complex disease that can result in progressive vision loss. It is the second leading cause of blindness, accounting for 23% of permanent blindness in Hong Kong. There are no treatments that restore vision lost to glaucoma. This study will examine the effect of transcranial direct current stimulation (NIBS) on improving quality of life, visual function and functional performance in patients with peripheral field loss due to glaucoma.
Age range from 18 to 80 years;
Diagnosis of primary open angle or normal tension glaucoma with relative scotoma in both eyes;
A relative scotoma defined as a Humphrey Field Analyser (HFA) threshold perimetry loss (mean deviation of -6dB) within the central 24 degree of the visual field for at least one eye;
Best-corrected distance visual acuity of 6/12 or better (equivalent to 0.3 logMAR acuity or better to confirm that participant's central vision is preserved).
Ocular diseases other than glaucoma (e.g. age-related macular degeneration, diabetic retinopathy, moderate to severe cataract) or severe hearing impairment (to ensure that participant can hear the instructions clearly during assessments and training);
Severe medical problems (e.g. stroke, Parkinson's disease) or self-reported neurological (e.g. brain surgery, brain tumor, peripheral neuropathy), or cognitive disorders (e.g. diagnosed dementia or cognitive impairment);
Self-reported vestibular or cerebellar dysfunction, history of vertigo;
Using any medications for any neurological conditions or psychiatric drugs (e.g. sedative, hypnotic) that might interfere motor control;
Crossover
NIBS
Other interventionAround 1 hour
VTS
Other interventionAround 1 hour
NIBS+VTS
Other interventionAround 1 hour
Sham
Other interventionAround 1 hour
Visual field test
Visual field test is measured monocularly using the 24-2 Swedish interactive threshold algorithm (SITA) standard tests by Humphrey visual field analyzer (HFA, Carl Zeiss Meditec Inc., California). The mean deviation (MD), pattern standard deviation (PSD), and visual field index (VFI) are recorded, and the MD of the 24-2 visual field test will be used as the primary outcome of intervention effect.
Electroencephalography (EEG)
Electrophysiological function is assessed using a 64-channel high-resolution electroencephalography (EEG) system. EEG outcome measures include spectral power in the delta, theta, alpha, beta, and gamma frequency bands, with particular focus on alpha-band activity, as well as functional connectivity measures derived from scalp EEG recordings, including coherence, phase-based connectivity, and related network indices. Pattern-reversal visual evoked potentials (PR-VEP) are recorded during presentation of a high-contrast checkerboard stimulus to the central 20-degree visual field under monocular viewing conditions. Stimuli are presented at 0.5 Hz and 1.5 Hz with 40 reversals. PR-VEP outcome measures include N75 latency, P100 latency, N135 latency, and N75-P100 and/or P100-N135 amplitude.
Optical Coherence Tomography (OCT)
Retinal nerve fiber layer is measured using spectral-domain Optical Coherence Tomography (OCT). Peripapillary retinal nerve fiber layer thickness is obtained from a circular scan centered on the optic nerve head. Ganglion cell thickness is measure using macular OCT imaging
Optical Coherence Tomography Angiography (OCT-A)
Evaluation of retinal vascular function in glaucoma patients is measured. Detailed visualisation of microvasculature structure within the retina and optic nerve head is measured, change of ocular perfusion is shown.
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