Noninvasive Brain Stimulation for Visual Field Deficits

Inclusion Criteria: 1. 18 years of age or older. 2. Presence of some intact visual cortical areas (other than primary visual cortex) in the damaged brain hemisphere. This assessment will be made from MRI or CT scans of the subject's head, which will be obtained via standard release from their neurologist. 3. First ever ischemic or hemorrhagic stroke with damage to primary visual cortex, and rendered blind over a portion of their visual field. * Ischemic stroke patients will be either subacute (within 6 months of their stroke) or chronic (more than 6 months) * Hemorrhagic stroke patients will be chronic only (greater than 6 months) 4. Must demonstrate a clear deficit in either simple or complex visual perception in portions of their visual field as measured by visual perimetry. 5. Imaging evidence that the stroke is primarily affecting the visual cortex. 6. Willing and able to participate in the study protocol and to comply with study procedures. Exclusion Criteria: 1. No evidence of damage to the primary visual cortex. 2. Visual cortex damage as a result of a subsequent stroke (not primary). 3. Total cortical blindness, covering both left and right visual fields. 4. Unable to fixate visual targets precisely or unable to perform the visual training exercises as directed. 5. Complete loss of reading abilities. 6. Current or prior history of any neurological disorder other than stroke, such as epilepsy, a progressive neurologic disease (e.g. multiple sclerosis) or intracranial brain lesions other than the qualifying stroke lesion. 7. Current history of poorly controlled migraines including chronic medication for migraine prevention. 8. History of seizures, diagnosis of epilepsy, history of abnormal (epileptiform) EEG or immediate (1st degree relative) family history of epilepsy; with the exception of a single seizure of benign etiology (e.g. febrile seizure) in the judgment of the investigator. 9. History of fainting spells of unknown or undetermined etiology that might constitute seizures. 10. Past or current history of major depression, bipolar disorder or psychotic disorders, or any other major psychiatric condition. 11. Participants who are suffering from one-sided attentional neglect as determined by standard neuropsychological tests: figure cancellation and line bisection tasks. 12. Contraindication for receiving tRNS. 13. Chronic (particularly) uncontrolled medical conditions that may cause a medical emergency in case of a provoked seizure (cardiac malformation, cardiac dysrhythmia, asthma, etc.). 14. Any complex, uncontrolled/unstable or terminal medical illness. 15. Substance abuse or dependence within the past six months. 16. Medications will be reviewed by the responsible MD (Drs. Sandeep Kumar or Dan Press) and a decision about inclusion will be made based on the following: The patient's past medical history, drug dose, history of recent medication changes or duration of treatment, and combination of CNS active drugs. 17. All female participants that are pre-menopausal will be required to have a pregnancy test; any participant who is pregnant or breastfeeding will not be enrolled in the study. 18. Subjects who, in the investigator's opinion, might not be suitable for the study. 19. A hair style or head dress that prevents electrode contact with the scalp or would interfere with the stimulation (for example: thick braids, hair weave, afro, wig). 20. Additional criteria for Group 1b only: Contraindication for using VR technology, specifically an implanted medical device such as a pacemaker, implanted defibrillator, deep brain or vagal nerve stimulator. Participants with a history of seizures are already excluded per the above criteria.