This study evaluates the efficacy of visual perceptual learning for the treatment of visual field defect caused by brain damage. Half of participants will receive visual perceptual training using the Nunap Vision, while the other half will receive sham training using the Nunap Vision-C.

Inclusion Criteria:

• Age 19-80 years
• Brain damage-induced visual field defect
• At least 6 months after brain lesion
• Minimum of 4 testing locations, where measured threshold ≤ 20dB
• Verified visual pathway damage using CT or MRI
• K-MMSE(Korean Mini Mental Status Examination) score ≥ 24
• Visual acuity equal or better than 20/40
• Able to use the investigational device
• Patient/legally authorized representative has signed the informed consent form

Exclusion Criteria:

• Unreliable Humphrey visual field test (any of fixation loss, false positive, false negative ≥ 20%)
• Complete hemianopsia with sensitivity of the whole hemifield ≤ 3 dB
• Epilepsy, photosensitivity, Parkinson's disease
• Bilateral visual field defect
• Hemispatial neglect
• Ophthalmologic disorder that may interfere the trial
• Inability to discontinue psychostimulants such as methylphenidate, modafinil, and amphetamine.
• Candidate for carotid endarterectomy or stenting
• Received ophthalmologic surgery within 3 months, except for the cataract surgery
• Pregnant or breast feeding
• Participating in other clinical trial
• Any other condition that, in the opinion of the investigator, precludes participation in the trial