Cortically Blind Subject Inclusion Criteria:  Subjects between the ages of 17 and 75, who have sustained damage to primary visual cortex at age 17 or later, and are rendered blind over a portion of their visual field. Subjects must have 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. Subjects who demonstrate a clear deficit in either simple or complex visual perception in portions of their visual field. Subjects who are competent and responsible, as determined by the Principal Investigator. Subjects who will receive retinal electrophysiology (mfERG) testing must have a report from their ophthalmologist stating that they are able to receive dilating drops  Cortically Blind Subject Exclusion Criteria:  Subjects who do not possess damage of primary visual cortex or its immediate afferents Subjects who are suffering from an active disease process involving their nervous system. Subjects who are unable to fixate visual targets precisely with their eyes Subjects who have unreliable vision fields from prior testing indicated by greater than 20% fixation losses, false positives or false negatives Best corrected visual acuity worse than 20/40 in either eye Impaired foveal sensitivity as indicated by visual field tests Presence of vision loss from ocular disease or disorder Presence of bilateral visual acuity loss from any source Subjects who are suffering from one-sided attentional neglect Subjects who have impaired auditory thresholds that would influence test results and training efficacy (all our testing and training involves sound as a cue for trial/stimulus onset or as feedback) Persons who lack the competence or are otherwise unable to perform the visual training exercises as directed.  Control Subject Inclusion Criteria:  Subjects must be between the ages of 17 and 75 years of age Subjects must report no history of neurological disorder. Subjects who are competent and responsible, as determined by the Principal Investigator.  Control Subject Exclusion criteria:  Subjects who possess damage to the visual system Subjects who are suffering from an active disease process involving their nervous system. Subjects who are unable to fixate visual targets precisely with their eyes Best corrected visual acuity worse than 20/40 in either eye Presence of vision loss from ocular disease or disorder Presence of bilateral visual acuity loss from any source Subjects who are suffering from one-sided attentional neglect Subjects who have impaired auditory thresholds that would influence test results and training efficacy (all our testing and training involves sound as a cue for trial/stimulus onset or as feedback) Persons who lack the competence or are otherwise unable to perform the visual testing/training exercises as directed.