Brain Stimulation Effects on Orientation and Mobility Skills in Adults With Vision Impairment

Inclusion criteria

• Are healthy, capacitated adults with binocular constricted visual field loss (due to either retinitis pigmentosa (RP), rod-cone dystrophy, or advanced glaucoma) resulting in functional vision losses. These individuals with visual impairments can be those who have been previously trained by an Orientation and Mobility (O\&M) specialist to independently travel with the long white cane daily (since the length of the white cane and tip at the base are based on personal preference, they should be willing to use their own white cane for the study), and those who do not necessarily use a cane for travelling.
• Have binocular visual acuity or best corrected binocular visual acuity no worse than 6/12 or 20/40 or +0.30 logMAR (inclusive) with no eccentric viewing and binocular visual fields no better than 50 degrees in total in each eye as given by the Humphrey Field analyzer and no better than 50 degrees binocularly as given by arc perimeter test. The Humphrey Field Analyzer measures static visual field test, whereas the Arc perimeter test measures kinetic visual field test. Measuring kinetic and static visual field would promote a greater understanding of the individual's daily performance.
• Are over the age of 18 (inclusive) and has full legal capacity to provide informed consent.
• Have read and fully comprehends the information in the consent letter.
• Are willing and capable of adhering to instructions and maintaining the outlined appointment schedule.

Exclusion criteria

• Are involved in other recent eye-related studies, either clinical or research-related. To be eligible they would have to wait at least one week for studies not involving brain stimulation, and four weeks for studies in which they receive brain stimulation before they could participate in this study.
• Have been diagnosed with dementia or self-reported dementia with no formal diagnosis.
• Have been diagnosed with a cognitive impairment or self-reported cognitive impairment with no formal diagnosis.
• Have been diagnosed with physical or motor impairments resulting in walking and/or balancing issues or self-reported physical or motor impairments resulting in walking and/or balancing issues with no formal diagnosis.
• Have been diagnosed with vestibular disorders or dysfunctions which affects one's balance and/or mobility or self-reported vestibular disorders or dysfunctions which affects one's balance and/or mobility with no formal diagnosis.
• Are unable to follow the researcher's instructions.
• Are anticipating treatment (including ocular surgery) for any eye disease within the duration of the study.
• Have any ocular pathology in addition to retinitis pigmentosa (RP), rod-cone dystrophy, or advanced glaucoma, which can diminish their visual acuity and/or their visual field, however wearing glasses or contact lenses, as well as mild cataract of grade 2 or below is acceptable.
• Have severe hearing impairment.
• Are pregnant or trying to get pregnant.
• Fit any of the typical contraindicators for brain stimulation. See contraindicator section below.
• For all participants the contraindications for brain stimulation are:
• Diagnosed with epilepsy or have previously experienced an epileptic seizure.
• Implanted medication pump or implanted electronic device, including defibrillator or pacemaker.
• Any metal implants in the head (excluding tooth fillings).
• Active electric implants anywhere in the body (especially the head region).
• On psychoactive medication for any psychiatric or neurological conditions including but not limited to depression and schizophrenia.
• Areas of sensitive skin located on the face or head, or a skin condition on the face, or regularly use medication to alleviate skin irritation on the face.
• Recurring headaches.
• Previous head injury or skull fracture or head/brain surgery.
• Heart disease, neurological condition, or a history of cardiac or neurological surgery.
• Current or historical cancerous or noncancerous brain tumor, or other abnormalities in brain structure.