Visual agnosia

Visual agnosia is an impairment in recognizing objects through vision despite adequate basic visual abilities. It can affect object form, identity, faces, or other visual categories.

Apperceptive agnosia: A form of visual agnosia in which impaired visual integration prevents reliable perception of object shape. It shows how recognition can fail before a coherent object representation forms.
Prosopagnosia: An impairment in recognizing familiar faces that is not explained by basic visual loss. It is a category-specific form of visual recognition impairment.
Visual perception: The processes by which the visual system organizes information from light into representations of the environment. Agnosia is diagnosed when basic visual processing is sufficiently preserved for the task.
Visual neglect: A disorder of attention in which a person fails to respond to stimuli on one side of space, usually after brain injury. Neglect limits attention to visual input rather than specifically preventing object recognition.
Neuropsychological assessment: The evaluation of cognitive and behavioral abilities using standardized tests and clinical observation. Testing separates perceptual, naming, memory, and attention problems that can resemble agnosia.
Associative agnosia: A form of visual agnosia in which a person perceives an object's form but cannot connect it to meaning. It separates intact shape perception from access to object knowledge.
Pure alexia: An acquired impairment in reading caused by damage to visual word-processing pathways, often with preserved writing. It demonstrates selective failure to recognize a visually defined category.
Visual field: The area visible to an eye or pair of eyes at a given moment while gaze is fixed. Visual field loss must be distinguished from failure to recognize what falls within view.
Cortical blindness: Loss of vision caused by damage to visual cortex, despite functioning eyes. Unlike agnosia, cortical blindness removes or severely reduces the visual information available.
Visual evoked potential: An electrical response recorded from the brain after visual stimulation. It can help assess early visual pathway function when recognition is impaired.

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